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Load-Transfer-Based Micromechanical Simulation for Evaluating Elastic-Plastic Response of Discontinuous Carbon Fiber Reinforced Thermoplastics



The present study investigated nonlinear elastic-plastic stress-strain relations of discontinuous carbon fiber reinforced thermoplastics (CFRTPs) using experiments and numerical simulations. In the experiments, we conducted uniaxial tensile tests and three-point bending tests for two types of CF/PA6 specimens; injection-molded specimens with short fiber length and aligned fiber orientation and compression-molded specimens with long fiber length and random fiber orientation. Comparing the experimental results, we found that the injection-molded specimens showed a nonlinear stress-strain response, while the response of compression-molded specimens was almost linear. The results implied that long discontinuous fibers were effective for increasing the yielding point of the composites, even if the composites had a random fiber orientation, which was effective to eliminate the orientation dependence on mechanical properties of the composites. Furthermore, we attempted to simulate elastic-plastic stress-strain relations of discontinuous CFRTPs, in order to understand the effect of microstructure including fiber length. For this purpose, we employed fiber-based simulations to deal with the microstructure of fibers and matrix and the constitution law of matrix. The simulated results found that the fiber length is an influential factor on the nonlinearity of the stress-strain relations of discontinuous CFRTP composites.

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