Modeling and characterizations of mechanical behaviors of short carbon fiber and short glass fiber reinforced polyetherimide composites

As the major manufacturing methods for short fiber reinforced polymer (SFRP) composites, extrusion com-pounding and injection molding techniques usually lead to complex fiber length and orientation distributions in final composites for mechanical computation analysis. It is still a challenging task about how to accurately predict the comprehensive mechanical behaviors (tensile properties, damage evolutions and failure modes) of SFRPs from complicated microstructures. This work builds a new finite element model (FEM) based on the classical random sequential adsorption algorithm with genetic algorithm (GA) for high-efficiency geometrical construction for short carbon fiber and short glass fiber reinforced polyetherimide (SCF/PEI and SGF/PEI) composites. Fiber length and orientation measurements, single fiber filament and pure PEI tensile tests are carried out to support model establishment. It is found that the longer initial length would accompany with the longer final average length and the higher fiber volume fraction would bring about shorter average final length. Short carbon fibers with larger aspect ratios tend to be more preferentially aligned along mold flow direction than short glass fibers. The predicted tensile properties, damage evolutions and failure modes are in good agreement with experimental results. Finally, the effects of fiber volume fractions, orientations and lengths on the strength and modulus of SCF/PEI and SGF/PEI composites are quantitatively explored, respectively. Our proposed model can provide an efficient evaluation of the mesoscopic structure-property relationship of SFRP composites.