A Multiscale Approach to Investigate the Effect of Temperature and Crystallinity on the Development of Residual Stresses in Semicrystalline PEEK

Abstract

Thermoplastic Matrix Composites (TMC) are shown to have a considerable commercial interest in cutting-edge industries due to their superior mechanical and chemical properties and the resistance to high temperatures. During the processing, TMCs are subjected to a wide range of elevated temperatures involving different cooling and heating cycles which result in the development of internal residual stresses in the matrix. In semicrystalline polymers such as PEEK, formation of crystalline regions during the processing causes shrinkage in the matrix leading to generation of additional residual stresses. Optimization of materials, manufacturing and design of components reduces development cycle time and cost for future hightechnology applications of TMCs. It has been shown that manufacturing of TMCs has a huge impact on the microstructure of these material, which in turn control the in-service performance. Since the thermo-mechanical properties of composite materials are defined by phenomena at multiple length scales, to have precise estimation of these residual stresses, a computational approach is required to combine simulation tools at multiple length scale. In this study, a multiscale approach has been introduced based on the Integrated Computational Material Engineering (ICME) which integrates Molecular Dynamics (MD) and Finite Element Analysis (FEA) to predict the induced residual stresses during processing. In the first step, thermoelastic properties of semicrystalline PEEK are determined as function of crystallinity content at different processing temperature at nanoscale using MD and micromechanics modeling. In the next step, the evolution of thermo-elastic properties during the crystallization is achieved using computational and experimental data. These results will be used to estimate the induced residual stresses of composites at higher length scales. This two-scale approach will allow us to virtually characterize material properties and predict the residual stress state of composites during manufacturing as a function of processing parameters and investigate the effect of temperature and temperature history on semi-crystalline PEEK thermal-mechanical properties.