Interlayer Fracture Toughness of Additively Manufactured Unreinforced and Carbon-Fiber-Reinforced Acrylonitrile Butadiene Styrene

Abstract

Fused deposition modeling (FDM) has recently emerged as a promising method for rapid manufacturing of complex components in disciplines ranging from aerospace to biomedical. Despite the apparent advantage over other more traditional manufacturing methods, components manufactured using FDM are often highly anisotropic, having particularly low stiffness and strength in the direction of layer deposition. Additionally, poor adhesion between individual layers often leads to premature failure of FDM components, precluding their broader application in loadbearing structural applications. This study presents test method development for characterization of interlayer fracture toughness of FDM components with a modified double cantilever beam (DCB) test. DCB samples were manufactured with a commercially available 3D printer using unreinforced Acrylonitrile Butadiene Styrene (ABS) and chopped carbon-fiber-reinforced ABS (CF-ABS). Novel contributions of this work include 3D printing of DCB samples using unidirectional FDM layers, addition of reinforcing doublers to prevent DCB arm failure during loading, and insertion of 8 μm Kapton starter cracks mid-print. Fracture toughness values measured for ABS and CF-ABS showed that lowering temperature of the filament during extrusion, and inclusion of chopped carbon fibers, can have a deleterious effect on the interlayer mode I fracture toughness of FDM components. The toughness data obtained using the proposed test methodology demonstrates its suitability for design and optimization of FDM processes for improved interlayer fracture performance.