Influence of preheating on the fracture behavior of over-molded short/continuous fiber reinforced polypropylene composites

Over-molded composites (consist of short and continuous fiber composites) have been extensively used in automotive structures because of their lightweight, high strength-to-weight ratio, and ability to make complex profiles. However, the poor interfacial bonding between short and continuous fiber composites reduces the performance of the over-molded composites. The preheating process has been utilized to enhance the interface bond of the over-molded composites. In the present study, the influence of preheating on the fracture behavior was studied by conducting tensile, flexural, short beam shear, mode I and mode II interlaminar fracture tests on over-molded short/continuous fiber polypropylene composites. The experimental results of the preheated specimens demonstrated an enhancement of tensile, flexural and short beam shear strength by 15%, 221% and 17%, respectively, compared with non-preheated specimens. Further, preheating enhanced the mode I and mode II interlaminar propagation fracture toughness by 655% and 44%, respectively compared with non-preheated specimens.