Simultaneously enhancing the strength and toughness of short fiber reinforced thermoplastic composites by fiber cross-linking

In recent years, short fiber reinforced thermoplastic composites (SFRTPCs) have attracted significant interest due to their low density, high strength and toughness, environmental resistance and low cost. Currently, an important task is to optimize their internal structures so as to maximize their mechanical properties. Interestingly, a previous experimental study showed that by adding a small amount of a stronger material in the matrix to link up short fibers, the strength of SFRTPCs was enhanced. We note, however, that a micromechanical study on the effect of fiber linkage on the mechanical properties is still lacking. In this work, we have developed a finite element model to conduct such micromechanical analysis. In this model, the polymer matrix is taken as elastic-plastic material, the fiber as a brittle material following a brittle damage model, while the interphase and linkage as the same polymer following a progressive damage model. Our simulations show that for a SFRTPC with a given short fiber weight fraction, by increasing the weight fraction of the linkage material, the Young's modulus, yielding strength, ultimate tensile strength, and tensile toughness of the SFRTPCs are all increased. By increasing the strength of the linkage material, the ultimate tensile strength and tensile toughness of the SFRTPCs are increased. Modified rules of mixing have been proposed to consider the fiber crosslinking effect. The present study provides a useful reference for the optimal design of SFRTPCs to maximize their mechanical performance.