Design, Manufacturing and Applications of Composites
Enhancement of Energy Conversion Efficiency in Organic Solar Cell Using Nanoparticles
Doping nanomaterials such as the nanoparticles, nanorods, nanoprisms, etc. into composite organic solar cells (OSCs) have recently attracted considerable research interest to obtain higher energy conversion efficiency. Among them, doping of Ag, ZnO nanoparticles into photoactive layers of multilayered composite OSCs are proposed to enhance the photocurrent due to the localized surface plasmon resonance (LSPR) effect. The size as well as the geometry of these nanoparticles are the most important key factors to contribute to LSPR effect. In this work we have investigated the LSPR effects of Ag and ZnO nanoparticles on the photoactive layer in a regular structure of OSC as ITO/photo-active layer doped with nanoparticles/ buffer layer/Al. The photoactive layer such as P3HT:PCBM doping with nanoparticles can be modeled as the light absorbed medium in which its physics behavior is altered by LSPR. Changing the size of Ag and ZnO nanoparticles, i.e. the radius, in P3HT:PCBM active layers will tune their absorption spectrum. The mechanical properties of nanoparticles doping in OSC structures based on P3HT:PCBM will also be discussed.
Nguyen Nang Dinh, Pham Duc Thang, Dang Dinh Long and Nguyen Xuan Nguyen
The Braided Composite Used as Sealing Parts
Braided fabric has excellent mechanical properties as its structure shows the ability of long fiber bundle. The braided fabric is normally classified into three kinds; flat braided, round braided and square-braided, which according to the shape and manufacturing technique. In the square-braided fabric, the fiber bundles are continuously braided each other throughout the thickness and longitudinal direction. Therefore, it is used in braided composite as sealing parts. It do not show ravel or come apart in service that is the disadvantage of the round braided fabric. This study currently has focused on the relation between structure of the braided packing and mechanical behavior of the packing. Cyclic compression test was performed on the square-braided fabric. The hysteresis loop in load and displacement were investigated. From the results, mechanism of deformation on the square-braided packing was clarified.
Composite Sandwich Structural Super Capacitor
Structural capacitors have functions of load bearable structures and energy storable capacitors. Although a parallel plate type capacitor has advantage of high voltage resistance, the parallel plate capacitor has the drawback of low capacitance. An electric double layer capacitor of a composite structure using electrolyte polymer matrix has developed with glass fiber fabric separator. The electrolyte polymer, however, caused high internal resistance of the capacitor. In the present study, therefore, a new method to use sandwich form core that have high water retentivity is proposed and experimentally investigated. As activated carbon sheet is used as electrodes to make a supercapacitor. Woven carbon fabric is used as lead wires of the supercapacitor in the sandwich form core. The new method is expected to have low internal resistance and high capacitance. As a result, the new system realized 520 mF/cm2 and low surface resistance of 810 ï—cm2.
Characterization of Electrochromic Properties of Polyaniline and Polyethylenedioxythiophene based Devices
Polyaniline (PANI) and polyethylenedioxythiophene (PEDOT) onto ITO-coated glass samples were prepared by electro-polymerization. UV-Vis transmission spectra of the both films show that PEDOT films have a high transmittance in a range from 350 to 600 nm, whereas PANI films exhibit a light-green color. The PANI-PEDOT electrochromic devices exhibited a deep-blue coloration and a good reversible coloration /bleaching performance in 0.1M LiClO4 +PC electrolyte. The response time of the ECD coloration was found to be as small as 20 s and the coloration efficiency was found to be of 10.70 cm2 ï‚´C-1. This demonstrates that the electropolymerized PANI and PEDOT films can be served as a good candidate for complementary ECD smart windows, taking advantage of their excellent properties in terms of chemical stability.
Investigation of Mechanical Properties and Microstructure of Various Fabric-Reinforced Geo-Composite at Elevated Temperature
Series of experiments is used to investigate mechanical strength of various fabric-reinforced geocomposites at elevated temperature (up to 1000 oC). A correlation between increase in mechanical strength and the microstructure reliability of fabric reinforced geocomposites is established in elevated temperature range. The mechanical strength of the fabric reinforced geocomposites is investigated at elevated temperature in terms of physical, fire testing and thermal conductivity. The result proves that the strength of carbon based geopolymers increased towards higher temperature that strongly correlated with development of various microstructures. Fire testing was conducted on 3 mm thick panels with surface exposure of region 14 x 90 mm. The fires rating more than half an hour were achieved with resistance to shrinkage cracking exhibited as important parameter. The microstructure of geocomposites shows large pores towards 600 ºC, that indicated lower in mechanical strength. On increasing the temperature, microstructure of carbon based geocomposites shows oxidized layer and very homogenous layer with less porosity. As a result the mechanical strength increases on increasing the temperature and developing oxidized layer. Fiber reinforced composites may be considered as an alternative to improve flexural strength and fracture toughness at elevated temperature. The carbon reinforced geocomposite proves as one of the suitable candidates for the high temperature applications such as thermal barrier and fire resistant panels.
Self Healing Materials for Low Temperature Applications
This work investigates the feasibility of structural self-healing of Fiber reinforced Polymer Composites (FRPC) using microencapsulated monomer/catalyst system for low temperature applications. Microcapsule containing liquid 5E2N monomer in poly melamine urea formaldehyde (PMUF) shells have been synthesized following the insitu emulsion polymerization technique. Free flowing microcapsules of average size ranging from 200 μm down to 20 μm have been successfully produced. Healing agents (catalyst particles and microcapsules) are dispersed into the resin using vacuum centrifugation technique. Feasibility of self-healing of cracks in cured resin samples containing the healing agents is demonstrated by visually observing the flow of monomer filling and healing the cracks. Methods are developed to evaluate the quality of self-healing in FRPC samples containing initial mid layer flaw. Healing agents dispersed in resin are applied between the mid layers of dry carbon fabric to manufacture FRPC laminate using hand lay-up method in autoclave. The load-unloadheal- load steps within the ASTM test protocol has been employed to study the healing effects of FRPC. Composite samples containing different average sizes and weight percentage of microcapsules are tested to understand their effect on self-healing performance. Test results are compared between no healing (without healing agents) and healing (with healing agents) specimens.
Process Parameters on Deep Drawing of Fiber Reinforced Thermoplastic Composites
Manufacturing technologies of fiber reinforced plastics (FRPs) are an essential and promising area for the automobile, marine, and aerospace industries in order to cause an increase in production rate, reduction in labor cost, and improvement in processing accuracy. The deep drawing process contributes to rapid processing time, product consistency, complex design, saving material waste, and high cost efficiency. Thermoplastic polymers are suitable to a blank of this process since they soften when heated and harden upon cooling, i.e., a reversible process. Therefore, the development of inexpensive and fast cycle processing technologies for FRPs is a significant key factor to boost the availability of high-strength and lightweight FRPs. Herein, we assess the influence of process parameters on the application of fiber reinforced thermoplastic composites to deep drawing. The interested range in processing temperature is between the glass transition temperature and melting point of thermoplastic composites. The experimental study of deep drawing is undertaken to evaluate the formability of FRP materials. This study found the appropriate temperature distribution through thickness of the blank and the minimum value of the blank holder pressure in order to produce products with good appearance by deep drawing.
Yuki Matsuno, Kazuya Kitabayashi and Michihiko Hosihino
Effects of Process-Induced Fiber Bundle Waviness on the Flexural Strength of Carbon Fiber Reinforced Thermoplastic Composites
This study focuses on the process-induced fiber bundle waviness in carbon fiber reinforced thermoplastic composites (CFRTP). Fiber bundle waviness is often observed in manufactured CFRTPs, which deteriorates the mechanical properties. This study experimentally investigates the quantitative measurement of fiber bundle waviness in unidirectional CFRTP using the optical microscope and the X-ray CT scanning. Flexural mechanical properties are measured in relation to the magnitude of the included fiber waviness. Strength deterioration is experimentally evaluated as a function of the fiber waviness parameter.
Kotaro Akakabe, Takahira Aoki and Akira Kobiki
Influence of Molding Condition on Process- Induced Strain of Reinforcements
In the present study, the evaluation method for process-induced stress of thermosetting FRP has been developed by in-situ strain evaluation using an FBG sensor and a viscoelastic FEM analysis. A model specimen of glass optical-fiber reinforced polymers where the FBG sensor were embedded, was manufactured for the evaluation. From the experimental results, it was found that cure shrinkage strain as well as thermal strain should be considered for evaluating residual stress in reinforcing fibers. The mechanical properties of resin used for the simulation were represented as functions of degree-of-cure and temperature. Since the FEM results agreed well with experimental result, it was found that viscoelastic properties, thermal expansion and curing shrinkage of resin play significant roles for generating process-induced strain of fibers. In addition, simulated results show that the process-induced strain decreases when heating rate is smaller.
Cure Cycle Optimization of Out-of-Autoclave Composites Based on In-Process Cure Strain Monitoring
Aerospace-grade CFRPs are mainly manufactured under high pressure using an autoclave to achieve high quality. The method, however, has enormous costs during installation and operation, and it is also time-consuming. Therefore, out-of-autoclave (OOA) method is recently attracting considerable attention to overcome these disadvantages. There are several OOA methods such as filament winding and vacuum assisted resin transfer molding. Among them, prepreg based vacuum bag only (VBO) method is a promising one for aerospace applications due to high fiber volume fraction and the similarity to the autoclave method. Several studies on VBO were conducted and considerable insight into void formation was obtained. However, they focused on only void and did not investigate the internal states such as residual strain which significantly affects the mechanical properties after molding. Therefore, in this study we measured strain development during VBO cure processes using fiber Bragg grating (FBG) sensors. First, we proposed a novel cure cycle (Modified cycle) in which the cure temperature is controlled to be lower than Tg during the heating. Then, we measured internal strain for specimens fabricated using manufacturer’s recommendation cure cycle (MRCC) and modified cycle. In modified cycle, the residual strain was considerably reduced compared with that in MRCC. Finally, we conducted tensile tests to evaluate the validity of the modified cycle, showing that the higher strength can be achieved using the proposed cure cycle.
Shinsaku Hisada, Kazunori Takagaki and Shu Minakuchi
Worker's Skill Comparison and Analysis of Mechanical Property
It is difficult discovering the optimal conditions for molding, as VaRTM molding requires perform manufacturing process which makes the fiber base material fit into a three-dimensional shape by applying pressure and heat. It is said that the accuracy of the preform affects the mechanical properties of the molding product. In recent years, despite continued investigations into the automated manufacturing of preforms, it was still causing the accuracy of the preform to be dependent on the ability of the worker. In this research, we made three subjects with varying number of years’ experience create preforms and produce a VaRTM molding. The test results for comparing the mechanical properties of the molding product, on the one hand, they revealed a higher intensity in order of the most years of experience to least. On the other hand, results reversed to what was intend at all. Based on the fact that there were differences in the accuracy of the preforms, while optimizing the creation of systems which produce exactly the same accuracy, regardless of the worker manufacturing the preform, we will continue to conduct research that leads to the development of automated production technology.
Kentaro Hase, Tomoe Kawazu, Aya Miki, Tadashi Uozumi, Akihiko Goto and Hiroyuki Hamada
Manufacturing of Thermoplastic Composite Rods using Vacuum Assisted Pultrusion
Pultrusion is an automated composite manufacturing process allowing the continuous production of constant cross-section beams. Pultrusion has been successfully used in the industry with thermoset matrixes. The pultrusion of thermoplastic matrix composites, however, has not reached the same level of industrial penetration. This can be attributed to the viscous thermoplastic polymer melts. Their high viscosity hinders the impregnation flow of the reinforcing fibers, resulting in porous composites. The aim of this study was to reduce the porosity of pultruded composites. The addition of a vacuum chamber was used to extract entrapped air in the composite during pultrusion. The pultrusion system is also equipped with 31 thermocouples, 2 load cells and a rotary encoder to acquire processing parameters. Different material systems were used: Carbon fibers with Nylon polymer as well as bio-sourced flax fibers and PLA polymer. The reinforcement and polymer, procured as filaments, were first combined in hybrid yarns. Pultrusion experiments were done at 50 mm/min with or without vacuum. Pultruded rods’ consolidation quality was assessed by microscopy. It was observed that the addition of the vacuum chamber can reduce the porosity. These results are promising features that may allow the largescale production thermoplastic composite pultruded parts.
Development of Finite Strain Shell Elements for Multi-Layered Fiber-Reinforced Materials Applied for Non-Rigid Parts Deformation during Assembly Process
Non-rigid parts in assembly process may have different shapes in a free state compared to the designed (nominal) model due to geometric variations, gravity loads and residual stresses. This may make the assembly process difficult, even impossible. For multi-layered fiberreinforced composite non-rigid parts, it becomes much more complex. Therefore, studying the material behavior of fiber-reinforced non-rigid parts during an assembly process is very important. This paper describes the development of a constitutive model for fiber-reinforced materials. An anisotropic hyperelastic material model with a polyconvex strain energy function was investigated and implemented in Abaqus as a user-defined material used with finite strain shell elements. An inverse characterization method was applied to identify the parameters of this material model based on experimental measurements.
Vincent Francois, Jean-Christophe Cuilliere and Xuan-Tan Pham
Non-destructive Evaluation for Chemical Degraded GFRP
This paper describes the mechanical properties of GFRP after the immersion test in 10% sodium hydroxide and 30% hydrochloric acid solutions and vapors conditions at 40ºC. The bending strength and the flexural modulus of the sample immerged in sodium hydroxide solution for one month greatly decreased although these of the sample immerged in hydrochloric acid for one month did not change. It was also found that there was a large difference of ultrasonic echo level between before and after immerged samples in sodium hydroxide solution. NaOH is attacked surface of GFRP and HCl is penetrated in GFRP.
Keisuke Ono, Akihiro Wada and Hiroyuki Nishimura
Impregnation Behavior During CFRTP Pipe Fabrication by Simultaneous Heating in Textile Preforming Process
In general, to product carbon fiber reinforced thermoplastics (CFRTP) a press molding machine and a mold are necessary. These initial equipment costs cause the increase in the production cost. An open mold method without using a mold is expected to reduce the production costs. Therefore, in this study, an open mold method have been developed. In the new molding method, an intermediate material, the stretch broken yarn with PA12 (SBY) was used. CFRTP pipe was fabricated by simultaneous heating in braiding process. The reinforcements were braided structure with 40 degree fiber orientation angle to the longitudinal direction. CFRTP pipes were molded by changing heating position in order to investigate the relationship between impregnation states and heating conditions. The impregnation states were quantified by measuring un-impregnation area from the cross-sectional observation after molding. Impregnation process was clarified by thermographic measurement and crosssectional observation of the molded composite. Furthermore, impregnation mechanism was clarified as below, (1) The braiding yarn was heated in individual and was impregnated before braiding point, (2) Braiding yarn was compressed to the mandrel by the tension at the braiding point．
Processing and Thermal Response Properties of Temperature Sensitive Gel/Polymer Composites
Many kinds of temperature sensitive gels (TSG) were developed currently. TSG were used in various fields such as medical, industrial and daily life. TSG having a lower transfer temperature at around 60ã€œ100 deg. C. were desired in order to expand their further applications and due to the reason of energy saving at the time of softening. In this study, we prepared TSG having a lower transfer temperature, which became more toughness than that of existing TSG because the side crystalline chains were introduced into the polymer structure. The developed TSG also were compounded to polymer composites with different filler composition. In order to clarify mechanical and thermal properties of developed TSG/polymer composites films, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA) and tensile mechanical testing were performed. These results showed that the transfer temperature of TSG was at around 60 deg. C. The form reversibility of these composite films depended on the transfer temperature to a certain degree. Modulus of TSG composites films was significantly improved by almost 3 times as compared to that of matrix polymer, and the elongation at break of TSG composites film was also increased as compared to that of TSG.
Jin Gong, Hiroshi Ito, Yoshikazu Shibata, Dai Nakanishi and Shin-ichiro Ishihara
Effect of Surface Microstructure on Conjugation behaviors of Joining Process for Polymer-Metal Hybrid Material
Recently, polymer-metal hybrid (PMH) material plays a key role in the various field of automotive parts, electronic devices, and medical equipment. In this research, polyphenylene sulfide (PPS)/aluminum joining molded was successful developed which modified micro-structure on the aluminum surface by using an injection molding for joining process. The results show that the joining strength as the maximum load and the maximum stress were increased by increasing groove height and groove number, but the crystallinity did not change by using different of groove height and number of the groove at the same of annealing process. The 2 kinds of conjugation behaviors were obtained after adhesive test as matrix-fracture-like and cohesive-failure-like. The obtained PPS groove height 40-70 μm indicated the cohesive failure, while the higher value indicated the matrix fracture, at the height about 70 μm is considered to be critical boundary point of the 2 behaviors.
Development of Real-Time Cure Monitoring System of FRP Laminates
Our study focuses development of real-time cure monitoring system for FRP prepregs using Fresnel-based fiber-optic sensors. The sensor can measure changes in refractive index of resin and degree-of-cure can be calculated from the measured value and temperature. However, during hot-press molding using prepregs, the sensor outputs show large fluctuation induced by air-voids near the sensor tip before melting temperature of B-stage matrix, and the fluctuation decreased measurement accuracy. In the present study, calculation method of degree-of-cure was improved using measurement of absolute refractive index of resin. In addition, a real-time filter was introduced into the monitoring system for elimination of the noise effect. The experimental results were discussed in comparison with cure process simulation. From the results, it appeared that the present monitoring system could measure degree-of-cure of FRP prepregs precisely in real-time.
Cure Monitoring and Simulation of Textile CFRP by Optical Fiber Sensors
In the present study, Fresnel-based fiber-optic sensors were used for cure monitoring of textile FRP. First, degree-of-cure curves of resin were measured by the fiber-optic sensors and DSC analysis. Comparing the curves by fiber-optic sensors and DSC analysis, it appeared that the degree-of-cure curves by the two methods agreed well with each other. Second, the cure monitoring of textile CFRP was conducted with heating temperature of 80°C. It was found that the degree-of-cure curve of CFRP was almost the same as that of matrix resin. Cure process simulation was conducted using a kinetic model obtained from DSC analysis and fiber-optic sensing. The simulated results showed good agreement with the experimental results. Moreover, it was confirmed that this method can be used for real-time simulation of degree-of-cure and control of molding temperature. Next, the GFRP which the temperature distribution occurred was conducted multi-point cure monitoring. It was able to measure the distribution of the degree of cure. It has been found that multi-points measurement of the degree-of-cure was useful to estimate distribution of degree of cure of FRP.
An Investigation on Skillful Techniques and Quantified Instructional Tool on Spray-up Fabrication Method
Spray up fabrication method has been used for forming composite structures since ancient times. On the other hand, spray up work itself relies on human skills, which means that the finish differs according to the operator carrying out the work. Hence highly specialized control technique and the tradition of skill are required to ensure the consistent stability of product quality. Generally, it needs more than 10 years of training and practice, as well as relentless efforts and an instinctive sense of molding to master the art of spray up; there are in fact very few people who can be called experts of the technique in Japan. For this reason, the tradition of molding techniques needs to be carried on as quickly as possible. In this study, the authors thus conducted a motion analysis experiment using spray up experts as subjects. The experiment, seemingly a new and only attempt in Japan, quantified techniques that are not visibly apparent and considered to be tacit knowledge. For this reason, motion analysis of the spray up method process was conducted to obtain objective data on an expert applier’s skills (the default value). It was also suggested that highly specialized control techniques, the appropriate training of non-experts, and technical tradition are possible.
Techniques for Preparing Random and Unidirectional Preform for Coconut Fibers Reinforced Composite
The preform production is of virtual importance for the manufacturing fiberreinforced composites. The distribution and orientation of the individual fibers in the preform significantly affect the mechanical properties of the later composites. This paper presents the techniques for preparing random (non-oriented) and unidirectional (UD) preforms for coconut fiber-reinforced composites. The experimental results confirm that the length and the state (wet or dry) of coconut fibers in the random (nonoriented) preforms affects the mechanical properties of random coconut fiberreinforced composites. The effects of techniques of random preform preparation on the mechanical properties of composites were investigated for various fiber volume fraction. It was found that the preforms prepared from wet coconut fibers show higher and more stable properties. On the other hand, the research also presents a technique to prepare straight coconut fibers for UD preform production. Several parameters such as composite processing method, experimental conditions of chemical treatment were examined for UD preform based composites.
Truong Chi Thanh, Nguyen Minh Tri, Nguyen Van Viet and Huynh Van Ton
Coconut Fibers Reinforced Polypropylene Composite: Investigation of Production Parameters using Compression Molding
The abundant coconut fibers in Mekong Delta – Vietnam were used as reinforcement for composite to improve the economic value of coconut trees and the income of farmers who earn their living with this type of plant. Moreover, the development of the coconut fibers reinforced composite also aims to protect the environment. This paper present the technology for extraction of non-oriented coconut fibers from their husks by machine aiming to obtain quality fibers with high recovery rate. The fibers then were used to produce polypropylene composite utilizing conventional compression molding. To optimize the mechanical properties of the resulting composite, the process parameters of compression molding including temperature, holding time and pressure were investigated. It was suggested that at fiber volume fraction of 45%, compression molding with temperature of 180 0C, pressure in the mold cavity of 90 kg/cm2 (equivalent to pressure in the cylinder of the press 110kg/cm2) held in 4 minutes provides a polypropylene composite reinforced with random coconut fibers with good mechanical performance.
Nguyen Minh Tri, Cao Luu Ngoc Hanh, Truong Lam Quynh Nhu, Aart Willem Van Vuure, Ignaas Ve
Novel Durable Biocomposites from Biobased PC/PLA Blend Matrix System
High performance polycarbonate (PC) and poly(lactic acid) (PLA) blends were created using compatibilizer and impact modifier with the aid of commercially available industrial chain extender. Atomic Force Microscopy studies have shown that the additive phase concentrated exclusively in brittle PLA phase ensuring high efficiency of impact strength modification with relatively small amount of modifier in composites. The small amount of glass fiber loading allowed the new PC/PLA blend based composites to maintain excellent elongational properties and impact strength. It was found that PLA and PC phases form co-continuous morphology in blend allowing the blend reaching high heat resistance of over 130 ºC which can be further increased in glass fiber composites. A competitive mechanical property (as compared to commercial PC/ABS composites) as well as relatively low density makes new biocomposites suitable for wide range of structural and durable applications.
Design Exploration of Non-crimp Fabric for Resin Transfer Molding by the GP using AIC and TOL
This paper reports on a study in which the architecture of non-crimp fabric (NCF) was optimized to improve its stiffness and permeability. The selection of design variables in shape optimization is extremely important, but in many cases the appropriate criteria to use in choosing those design variables are unclear. This study investigated a proposed method for extraction of effective design variables. In the proposed method, Pareto solutions are first obtained by preliminarily optimizing a simple NCF model with a few design variables. The effective design variables, including dependent variables, are then extracted from the obtained Pareto solutions. In-plane and out-of-plane stiffness and permeability values are also calculated in the optimization process using the homogenization method in liquid and solid phases as objective functions. Further, the relationship between the design variables and the objective functions are determined by applying genetic programming (GP) with the akaike information criterion (AIC) and tolerance (TOL) to the Pareto solutions. The results of analysis indicated that constriction and waviness of the fiber bundles improved the performance of the NCF. Consequently, the model was again optimized, with special focus on constriction and waviness, to ensure its utility as a design guideline. The optimized model simultaneously improved the elastic modulus and permeability coefficient of the trade-off relationship—thereby verifying the efficacy of the proposed method.
Ryosuke Matsuzaki, Tomonaga Okabe and Shigeki Yashiro
Homogenization of Viscoelastic Composite Reinforced Woven Flax Fibers
Natural fiber reinforced composites (NFRC) are used in several applications because of their good specific properties, eco-friendly characteristic and low cost. Moreover, due to the viscoelastic behavior of natural fibers, NFRC could present high damping capacity that is an important characteristic required in several structures supporting high dynamic load. This work aims to investigate the viscoelastic behavior of woven natural fiber reinforced composite, especially, its damping property. Firstly, an analytical homogenization model of woven natural fibers is established. This homogenization model is based on iso-strain model and correspondence principle. Experimental tests were carried out in order to validate the homogenization model. The result shows a good agreement between the homogenization model and the experimentation. By using the model, the properties, especially the damping capacity, of woven natural fiber reinforced composites was determined and compared with other synthetic fiber reinforced composites (SFRC).
Nonlinear Buckling and Postbuckling of an Eccentrically Stiffened E-FGM Circular Cylindrical Shells Resting on Elastic Foundations in Thermal Environment
Based on the first order shear deformation shell theory, this investigation presents analytical formulations and solutions for the nonlinear buckling and postbuckling of imperfect eccentrically stiffened E-FGM thick circular cylindrical shells on elastic foundations in thermal environments. It is assumed that the shell is a mixture of metal and ceramic by exponential distribution law (E-FGM) and its properties depend on temperature. The shell is reinforced by the eccentrically stringers and rings stiffeners made of full metal. The Galerkin method is applied to determine load–deflection curves. The influences of inhomogeneous parameters, dimensional parameters, stiffeners, elastic foundations, initial imperfection and temperature dependent properties on the buckling and postbuckling of thick FGM circular cylindrical shells are discussed in detail.
Dynamic Response Analysis of CFRTP Cylindrical Member for Front Collision of Automobiles
CFRP cylindrical member have high energy absorption performance under axial compressive load. Carbon Fiber Reinforced Thermo Plastics (CFRTP) will be useful for structural material of a shock absorber in the various industries. And in order to evaluate the behavior of this composite, several experimental study and numerical simulations using FEM are carried out recently. However, it is difficult to simulate the crushing behavior of CFRTP cylindrical member with progressive crushing by the FEM, because the crushing mechanism contains various kinds of fractures such as delamination and micro buckling and so on. In the present study, we developed cylindrical CFRTP member designed and fabricated for the purpose of designing impact energy absorption members under fulllap collision. Drop weight impact tests were carried out to investigate impact response behaviors and impact energy absorption characteristics of the cylindrical CFRTP member. Also, a finite element (FE) model was developed by using the nonlinear, explicit dynamic code LS-DYNA to simulate the progressive crushing behaviors and absorbed energy of the cylindrical CFRTP member under impact loading.
Yuma Otsuka, Hitoshi Yamada, Katsunari Muranaka and Yoshio Aoki
Free Vibration of Rotating Functionally Graded Material Cylindrical Shells with Orthogonal Stiffeners
In this paper, free vibration analysis of rotating functionally graded cylindrical shells with orthogonal stiffeners is presented. Based on Love’s first approximation theory, using energy approach, the governing equations of motion which take into account the effects of initial hoop tension and also the centrifugal and Coriolis forces due to rotation are derived. To validate the present analysis, comparisons are made with those available in the literature for particular cases; very good agreements are achieved. The influence of the power law index and rotating speed on the natural fundamental frequency of the simply supported rotating stiffened functionally graded shell are investigated.
Application of X-Ray Microtomography and Dual Kriging to the Analysis of High Performance Composites
Accurate description of the complex architecture of fibrous woven reinforcements in composites is required for detailed numerical simulation of material manufacture, especially of textile compression and impregnation. Volume imaging techniques like X-ray microtomography provide information on realistic geometry, but require optimization to be efficient in practical applications. We propose a dual kriging-based method for reconstructing the continuous model of the textile reinforcement applied to data extracted from micro-tomographic scans. The smoothness of the model is controlled by the nugget effect. The discretization scheme based on the curvature energy of the fiber tow cross-section. This approach decreases the computer memory requirements by a factor of 500 compared to the initial X-ray scan.
Fracture Morphology Characterization of Unidirectional CFRP and CFRTP Composites
In this study, typical thermoplastic resin polyamide 6 (PA6) and thermosetting epoxy resin were used as matrices to manufacture unidirectional (UD) carbon fiber (CF) reinforced PA6 resin plates (CF/PA6) and epoxy resin plates (CF/Epoxy) to investigate their fracture morphology characterization through using tensile tests, microscope observation and scanning electron microscope (SEM) observation methods.
Toshi Sugahara, Yiyi Zhang, Yuqiu Yang and Hiroyuki Hamada
Nonlinear Dynamic and Vibration Analysis of an Eccentrically Stiffened E-FGM Plate in Thermal Environment
This paper investigated the nonlinear dynamic and vibration of eccentrically stiffened functionally graded plates under temperature using an exponential distribution law (E-FGM). Both E-FGM plate and stiffeners are deformed under temperature. The formulations are based on the classical plate theory taking into account geometrical nonlinearity, initial geometrical imperfection, temperaturedependent properties and thermal stresses in both plates and stiffeners. By applying Galerkin method and using stress function, effects of geometrical properties, temperature and eccentrically stiffeners on the nonlinear dynamic and vibration of the eccentrically stiffened E-FGM plate in thermal environments are analyzed and discussed.
Optimal Design of High Pressure Toroidal Tank Produced by Wrapping with Durable Composite
Structure - technology solution for light, high-pressure toroidal tanks with high strength composite materials, applicable to structures in missiles, flying and special devices, is proposed. The basic equations for calculation of the structure parameters of these tanks has been built. Based on these equations the designs of high-pressure toroidal tanks for an anti-ship missile and a special device has been realized. Calculation results indicate that the designed composite tank’s weight may be reduced significantly, compared to similar tanks made from high-strength steel.
Static Analysis of Functionally Graded Plates using the High-Order Shear Deformation Theory by MITC3 Plate Elements Having Strains Smoothed on Edges
The paper presents an efficient 3-node triangular finite plate element for static analysis of functionally graded plates using the high-order shear deformation theory (HSDT). The strain fields of the plate elements, which use the MITC3 technique to remove the shear-locking phenomenon, are smoothed on the edges of the elements to improve numerical demonstration. The proposed C 0-type plate elements, namely ESMITC3, need to two additional degrees of freedom at each node for solving functionally graded plates using the HSDT but shear correction factors of the plates are eliminated. The robustness and accuracy of the ES-MITC3 plate elements are evaluated by several numerical examples.
A Cell-Based Smoothed Discrete Shear Gap Method (Cs-Fem-Dsg3) for Non-Linear Dynamic Response of Laminate Composite Plate to Underwater Blast Load
The paper investigates the dynamic response of laminated composite plate subjected to underwater explosive loading. The cell-based smoothed discrete shear gap method (CS-FEM-DSG3) based on the first-order shear deformation theory (FSDT) and von-Karman non-linear kinematics are used to model the behavior of the laminated composite plate. The study is carried out in framework of a geometrical non-linear model of composite structures, in conjunction with the unsteady pressure generated by an underwater explosion. The effects of the number of layers and fiber of orientations to behavior of laminated composite plate are discussed. Numerical results demonstrate the accuracy and reliability of the present method compared with previous published methods.
Weibull Modulus of Post-Cracking Properties of Ultra-High-Performance Fiber-Reinforced Concretes
The Weibull modulus “mâ€ indicating brittleness of ultra-high-performance fiberreinforced concrete (UHPFRC) were statistically investigated according to the size effect on their uniaxial tensile behavior. The studied UHPFRC contained 1% macro twisted and 1% micro smooth steel fibers by volume. Tensile specimens were designed to have identical section shapes (constant ratio of width to thickness) as follows: 25×50×125, 25× 50×175, 25×50×250 and 50×100×250 mm3. The Weibull modulus values were obtained from size effect not only on post-cracking strength but also on strain capacity and toughness. The derived Weibull modulus values of UHPFRC were then discussed.
On the Elastic Properties of Heterogeneous Materials Containing Cubic Inclusions: Fourier Series Versus Finite Element Method
Both analytical and numerical methods are developed to deal with the effective elastic properties of composite materials containing cubic inclusions. In the framework of the analytical method, the elastic Hill tensor required for the calculation of the effective elastic tensors is obtained explicitly in terms of Fourier series. Numerical method is realized on the representative elementary volume of the medium using FEM. A perfect fit between the two developed method is observed.
The Dynamic Analysis of Laminated Composite Plates Resting on Viscoelastic Foundations Subjected to a Moving Harmonic Load Using Moving Element Method
In this paper, a recently developed method, namely Moving Element Method (MEM) is employed to investigate dynamic responses of the laminated composite plates resting on viscoelastic foundations subjected to a moving harmonic load based on the first-order shear deformation theory (FSDT). By using the MEM method, the laminated composite plate is discretized into “moving-elementsâ€, which are not physical elements fixed to the plate but are conceptual elements that “flowâ€ with the moving load through the plate. The governing equations of motions as well as the structural matrices of moving elements are formulated in a coordinate system attached to the moving load. Thus, the proposed method eliminates the need of keeping track the location of moving load with respect to the plate. The accuracy and reliability of the proposed method are verified by comparing its numerical solutions with those of other available numerical results. A parametric examination is also conducted to determine the effects of various parameters on the dynamic responses of the laminated composite plates resting on viscoelastic foundations subjected to a moving harmonic load.
Luong Van Hai, Tran Minh Thi and Nguyen Trong Phuoc
Analytical Estimation of Impact Damage and CAI Strength
Significance of the damage to low velocity foreign object impact in quasi-isotropic composite laminates and the residual compressive strength of the damaged plates are theoretically evaluated to estimate the CAI strength of the composite laminates. The damaged portion is modelled as equally spaced multiple circular plates without delamination opening which is a rough but mechanically acceptable approximation of the impact damage for damage growth stage as well as the compression behavior of damaged plates. Superposition technique is used to derive approximate closed-form formula for both the impact and compression problem. The expressions of the energy release rate derived as a function of geometrical and material parameters are able to predict the damage initiation and growth of both problems.
Effect of Fiber Architecture on Acoustic Emission Characteristics of Glass/Polyester Composites
This study discussed the acoustic emission (AE) characteristics of different kinds of glass fiber reinforced unsaturated polyester composites under static tensile loading. Two types of AE sensor with different resonant frequency were adopted to distinguish the fracture type; matrix dominated or fiber dominated fracture. Glass fiber chopped strand mat, cloth and roving cloth were used as reinforcement and the AE characteristics of these glass fiber reinforced polyester composites under static tensile loading were discussed.
Frequency Effect on Fatigue Tensile Behaviour of Carbon/Epoxy Plain Weave Laminates under Different Hygrothermal Conditions
The purpose of this paper is to study the load frequency effect on the fatigue behaviour at different environmental conditions of a quasi-isotropic carbon/epoxy plain weave laminate containing artificial flaw under tensile loading. Dry and wet specimens were exposed to tensile load-controlled cyclic loading with a stress ratio R = 0.1 at room temperature (RT) and at 82°C for load frequencies of 7 and 15Hz under different stress levels. Allowable stiffness reduction as a failure onset criterion was used to determine the delamination propagation threshold under cyclic tensile loading at each frequency and environmental condition. The propagation of delamination was verified using the ultrasonic imaging (C-Scan) technique. The experimental results show that load frequency played a positive effect by increasing the fatigue life of specimens for two conditions (RT, 85%RH) and (82°C, Dry). However, for the condition (RT, Dry) higher load frequency tended to reduce the fatigue life of tested specimen at high stress levels while starting from certain lower stress level it tended to increase their fatigue lives. On the contrary at the condition of (82°C, 85%RH) the effect was reversed compared to that of (82°C, Dry).
Effect of Self-Heating of High Damping Rubber Bearings on Design Practice
Traditional design guidelines generally assume uniform temperature distribution, and the value of design temperature is chosen to be the ambient temperature under which the rubber bearing is intended to operate. However, when high damping rubber bearings (HDRBs) are subjected to cyclic loads, the energy dissipated by the bearings is converted into heat and this heat causes significant temperature increase in the rubber bearings. This phenomenon is known as self-heating. The preliminary result of this topic is presented in a presentation at a conference [1]. This paper is devoted to investigate the self-heating effect on the design practice by conducting a seismic analysis of a single-span bridge at different ambient temperatures (23oC, -10oC, - 30oC). The inside temperature of HDRBs under earthquake Type-II increases about 10oC and 5oC at 23oC and -30oC ambient temperatures, respectively. Since the temperature increases during an earthquake is considered not so large as that during a cycling loading test in Nguyen et al (2013), a seismic model for HDRBs at low temperatures should be based on the inside temperatures. The design temperature of the model is chosen to be the inside temperature of the bearings in the selected cycle of the sinusoidal loading tests.
Evaluation of Fracture Properties of CFRTP・ CFRP and GFRTP・GFRP Using Woven Fabric by High-Speed Tensile Test
In this study, static and dynamic tensile tests of woven fabric reinforced thermal and thermoset plastic composites (FRTP and FRP) were carried out and strain rates from 1×10^-3 to 1×10^2 were loaded in the two tensile directions of 0-degree and 45- degree with respect to the fabric directions with a servo hydraulic testing machine. The specimens of FRTP and FRP were composed of two different woven fabrics of carbon and glass fibers, and two different matrix resin of PA6 and epoxy. All of the specimens were fabricated with VaRTM process. The experimental results for the strength, strain and absorbed energy depended on the strain rates of the tensile test, except the 0-degree specimens of CFRTP and CFRP. The experimental energy absorptions in the 45-degree specimens of CFRTP and GFRTP demonstrated higher values than those of CFRP and GFRP in every strain rates.
Combustion Behavior of Carbon Fiber Reinforced Plastics
This paper describes the evaluation of the flame resistance on Carbon Fiber Reinforced Plastics (CFRP). CFRP have the both conflicting performance between the lightness and the toughness. Use of the CFRP has increased dramatically since it was introduced 40 years ago. On the other hand, it is difficult for CFRP to add the flame retardancy in getting use of vehicle and airplane. In order to increase demand for a safety, we embarked on the fundamental research of CFRP that includes flame retardant.
Yusaku Mochizuki, Aly Hassan and Hiroyuki Hamada
Mechanical Properties and Structure of Polyamide 6 / Polypropylene Blends and Its Composites
In this study, polyamide 6 (PA6) / polypropylene (PP) blends were fabricated by high shear process technology as novel polymer process. Moreover, PA6/PP/glass fiber (GF) composite and PA6/PP/carbon fiber (CF) composite were prepared using novel polymer blends, and it was molded by hot press. Internal structure and morphology of PA6/PP blends were observed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results of SEM and TEM observation were confirmed that PP domain in PA6 was micro- and nano-meter order were dispersed. In addition, nano-dispersion for the PP domain diameter was proceeded to a greater degree while stabilized by the addition of PP-g-MAH. Tensile and Izod impact tests revealed their mechanical properties of obtained polymer blends and its composites. Results showed the PA6/PP blends had higher breaking strain and impact resistance than that of neat PA6. However, PA6/PP blends were fabricated under a certain condition of excessive high-shear rotation. These blends showed considerably lower breaking strain and yield strength. PA6/PP/GF and PA6/PP/CF composites also showed higher bending modulus and bending strength than that of neat PA6.
Initial Studies on the Mechanical Properties of Geopolymer Mortar after Additive Stone Powder Treatment
Concrete is the most commonly used construction material. Its use by communities across the globe is second only to water. Geopolymeric binders appear to be an alternative to ordinary portland cement (OPC), due to high mechanical performances and environmental advantages. However the cost of geopolymer binders is still higher than OPC, it is one of the major factors explaining why this new product is not yet a current alternative. So the purpose of this research was reduced the cost of geopolymer binders by addition stone powder (SP) content but mechanical properties of mortar is still good enough to meet essential requirements of industries. In order to determine the optimal proportion of stone powder content in mortar, the influences of ratio of stone powder/geopolymer cement (SP / GC), effects of stone powder on mechanical properties of mortar were investigated in this study.
Strain Rate Effects on Tensile Behavior of Ultra High Performance Hybrid Fiber Reinforced Concrete
Strain rate effect on direct tensile behavior of ultra-high-performance hybrid-fiberreinforced concrete (UHPHFRC) containing two types of macro fiber, steel (S-) and polyamide (P-), and one type of micro fiber, polyamide (p-), at high strain rates (10 and 47 s-1) was investigated. The volume content of macro fiber was maintained as 1.0%, whereas that of micro fiber varied from 0.0 to 1.5%. The UHPHFRCs with steel macro fibers (S-UHPHFRC) produced much higher rate sensitive tensile behavior than those with polyamide macro fibers (P-UHPHFRC). As the volume content of micro polyamide fibers increased, P-UHPHFRC produced higher rate sensitivity on post cracking tensile strength whereas S-UHPHFRC showed lower sensitivity. A proper amount of micro polyamide fibers, 0.5% in this study, would noticeably improve the impact resistance of S-UHPHFRCs, especially for strain capacity and peak toughness.
Wettability of Flame-Resistant Magnesium Alloy on Graphite Sheet and Preparation of VGCF/ Magnesium Alloy Composites
Mg-5wt%Al-3wt%Ca (Mg-5Al-3Ca) alloy is the representative flame resistant magnesium alloy, which is developing to use the parts of transformation equipment such as train, automobile and airplane. In order to improve the mechanical properties of this alloy, the development of the composite with carbon fiber is one of the suitable solution. In order to obtain the high performance metal matrix composites, the estimation of the wettability between the reinforcement and alloy is important because of the estimation of the interface strength between alloy and carbon fiber, and the choice of composite preparation process. In this study, the wettability between the alloy and the graphite sheet with (002) oriented surface structure was estimated. The wettability at 573 K in vacuum is about 120 degrees, which is low wettability. In order to improve the wettability, Ni was coated on graphite sheet. By using Ni coating with 3.7 μm in thickness, the wettability was improved to 90 degrees. Then, 0.5 wt. % vapor grown carbon fiber (VGCF) dispersed Mg-5Al-3Ca alloy composites was fabricated by stir casting process. Ni was coated on welldispersed VGCF by electroless Ni plating. VGCF was dispersed uniformly without aggregation in matrix, and microstructure of matrix was very similar with the conventional casted Mg-5Al-3Ca alloy.
A Workflow for Liquid Composite Moulding Process Assessment
Liquid composite moulding (LCM) processes are of great interest to the advanced composites industry as it provides a means of efficiently processing complex parts with a process that can be automated. To design an LCM process a number of decisions must be made including constituent material selection, injection pressure, processing temperature, tool design, and ancillary equipment selection among others. There is currently no comprehensive methodology/workflow used to assess and/or design these processes. This paper lays out a structured approach for designing them. This approach combines a number of experimental characterization and simulation techniques to estimate the cycle time of an LCM process. The workflow begins by characterizing the constituent materials. Experiments to determine resin viscosity and cure kinetics, and fiber preform permeability are performed. Process simulation is employed to estimate the mould fill time as a function of temperature and compared to the resin working time vs temperature. The processing temperature and infusion time can then be determined. Once the processing temperature is identified, thermochemical analysis is performed to determine to the overall cycle time. A detailed explanation of this methodology and case study are presented in this paper.
Christophe Mobuchon, Navid Zobeiry, Goran Fernlund and Anoush Poursartip
Microstructure and Mechanical Properties of Mg/Zn Composites Fabricated by Spark Plasma Sintering for Biomedical Implants
Magnesium stands as the most promising candidate for temporary fixation implants due to its superior biological properties and comparable mechanical properties to those of human bones. However, the initial mechanical properties of Magnesium are insufficient for these applications. In the present study, magnesium composites with 5 or 10 at% Zn were fabricated by means of the spark plasma sintering (SPS) method in order to enhance the mechanical properties. Intermetallic compounds formed by in-situ reaction between Mg and Zn were characterized by X-ray diffractometry (XRD) and energy-dispersive spectroscopy (EDS). Ascomposited microstructure observed by optical microscopy clearly revealed a quite homogeneous distribution of intermetallic phases with some aggregations. The hardness of these phases showed much higher values compared to that of Mgmatrix. The reactions are considered to strengthen the materials by producing hard intermetallic phases contributing as the reinforcements and enhancing the interfacial bonding between them and the matrix. The compression test results illustrated the much higher strengths of composites in comparison with those of pure magnesium. Hardness and compressive strength of composites indicated the good bonding between the matrix and reinforcement due to the same tendency in increasing of the values.
Effect of Polyethylene Terephthalate (PET) from Plastic Waste on Strength of Hot Mix Asphalt Concrete in Southern Vietnam
Waste plastic material, e.g. bottles, baskets, and bags, is one of urgent issues which cause environmental pollution these days around the world, especially in Vietnam. Waste plastic including Polyethylene Terephthalate (PET) - a type from plastic bottles in normal life can be used in asphalt mixture for enhancing the properties of mixture in terms of asphalt concrete performance in addition to solving disposal problem. In this study, waste plastic from mineral bottles is cleaned and cut into small dimensions by shredding machine before adding to hot mix asphalt concrete at high temperature. The hot mix asphalt concrete with and without PET are conducted through many experiments such as Marshall stability, indirect tensile strength, Cantabro abrasion loss test for strength evaluation of asphalt concrete. Many contents of PET also are evaluated in the study. Some results of Styrene-Butadiene-Styrene modified asphalt concrete are also included in order to show that PET from waste plastic bottle can be a promising additive or a thermoplastic polymer for hot mix asphalt concrete in aspects of strength performance in this study.
Study on Carbon Nano Fiber by Cotton Candy Method
In this study we focused on Carbon Nano Fiber (CNF) in the carbon-based nano materials’s field. CNF is expected to various applications. However, CNF have a high cost of production. Therefore, we are trying to reduce a cost to make a preparation of the CNF precursor using Cotton Candy Method (CoCaM). The CoCaM is a novel method that can fabricate large amount of nano fiber. The feature of CoCaM is used to forming a fiber with only air injection. Therefore, it is possible to make a cost saving by CoCaM, because it does not need to heating and using the electric field. We studied producing PAN nano fibers by CoCaM and carbonizing conditions for nanofibers. We found the factor that PAN concentration, air pressure and feeding speed affected diameter of nano fiber. The average nano PAN fiber diameter changed from macro- to nano- meters under the CoCaM. After carbonization, we obverted that CNF were same shape of the PAN nano fiber. However, the diameter of CNF was decreased. The Raman spectrometry of nano carbon fiber by CoCaM showed high crystallinity. It was found that the ratio of the D and G band intensities (ID/IG) of carbon nano fiber is 0.58.
Ryo Takematsu, Supaphorn Thumsorn, Masayuki Okoshi, Hiroyuki Inoya, Hiroyuki Hamada and Yo
Hybrid RCS frames consisting of reinforced concrete (RC) column and steel (S) are used frequently in practice for mid to high-rise buildings. RCS frames possess several advantages from structural, economical and construction view points compared to either traditional RC or steel frames. One of the key elements in RCS frames is the composite shear wall consisting of several steel sections encased in reinforced concrete. Regarding the RC walls reinforced by more than one steel profile, namely “Hybridâ€ wall, although a number of researchers have focused on its various aspects, they are currently not covered by standards because they are neither reinforced concrete structures in the sense of Eurocode 2 or ACI318, nor composite steel-concrete structures in the sense of Eurocode 4 or AISC 2010. This paper is dedicated to present a tentative design model for hybrid walls with several embedded steel profiles subjected to combined axial force, bending and shear. The model is based principally on the design rules of Eurocode 2 and Eurocode 4. Particular attention will be paid to shear (longitudinal and transversal) resistances because preventing shear failure is one of the major concerns when designing a composite structural member. A strut-and-tie model is developed to evaluate the transverse shear resistance taking into account the contribution of the steel profiles. Furthermore, an analytical method is proposed for the prediction of the longitudinal shear stress at the concrete-steel profile interface which allows to design adequate shear connection of the profile to concrete. The proposed design model provides a faire estimation of the part of applied shear which is applied to the embedded steel profiles; this allows to take into account the influence of transverse shear on the combined axial force and bending resistance. When used with design values of bond and friction shear strength of Eurocode 4, the proposed design model gives a faire estimation of the longitudinal shear stress at the concrete-steel profile interface.