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.

包覆成型复合材料（由短纤维和连续纤维复合材料组成）因其重量轻、强度重量比高以及能够制造复杂轮廓而广泛用于汽车结构。然而，短纤维和连续纤维复合材料之间较差的界面结合降低了包覆成型复合材料的性能。预热过程已被用于增强包覆成型复合材料的界面结合。在本研究中，通过对包覆成型的短/连续纤维聚丙烯复合材料进行拉伸、弯曲、短梁剪切、I 型和 II 型层间断裂试验，研究了预热对断裂行为的影响。预热试样的实验结果表明，拉伸、弯曲和短梁剪切强度提高了 15%，与未预热的试样相比，分别为 221% 和 17%。此外，与未预热的试样相比，预​​热使 I 型和 II 型层间传播断裂韧性分别提高了 655% 和 44%。