Hybrid fiber reinforced thermoplastic composites, fabricated by overmolding technique, are a novel class of lightweight components that benefit from the high mechanical performance of continuous fiber reinforced thermoplastics (CFRT) as well as geometric complexity because of short fiber reinforced thermoplastics (SFRT) composites architecture. The heterogonous interface between CFRT and SFRT in the hybrid structure was generated when SFRT was injected on CFRT surface during overmolding processing. However, the unmatched thermal properties between SFRT and CFRT may cause the poor adhesion at the interface due to the variation of temperature. In this article, how the thermal gradient affects the interfacial properties of hybrid structures is investigated through numerical and experimental methods. The results obtained from the molecular dynamics simulation demonstrate that decreasing thermal gradient can accelerate the molecular diffusion across the interface. Thus, at lower thermal gradient, the gap at interface is gradually disappeared. The results of the interfacial strength estimated by tensile lap shear test method show that the interfacial shear strength is greatly improved by decreasing thermal gradient because of higher crystallinity and bigger spherulite size of PP matrix at interface. In addition, the fracture mechanism of hybrid structure is observed to evolve with thermal gradient.

中文翻译：

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热梯度对注塑包覆成型杂化纤维增强聚丙烯复合材料界面行为的影响

通过包覆成型技术制造的杂化纤维增强热塑性复合材料是一类新型的轻质组件，由于连续纤维增强热塑性塑料（CFRT）的高机械性能以及短纤维增强热塑性塑料（SFRT）复合结构的几何形状复杂性，使其受益匪浅。当在包覆成型过程中将SFRT注入CFRT表面时，会在混合结构中生成CFRT和SFRT之间的异质界面。但是，由于温度变化，SFRT和CFRT之间无与伦比的热性能可能会导致界面处的粘合性差。在本文中，通过数值和实验方法研究了温度梯度如何影响混合结构的界面特性。从分子动力学模拟获得的结果表明，降低的热梯度可以加速分子在界面上的扩散。因此，在较低的热梯度下，界面处的间隙逐渐消失。用拉伸搭接剪切试验方法估算的界面强度结果表明，由于界面处PP基体的较高结晶度和较大的球晶尺寸，通过减小热梯度可以大大提高界面剪切强度。此外，观察到混合结构的断裂机理随着热梯度的发展而变化。通过拉伸搭接剪切试验方法估算的界面强度结果表明，由于界面处PP基体的较高结晶度和较大的球晶尺寸，通过减小热梯度可以大大提高界面剪切强度。另外，观察到混合结构的断裂机理随着热梯度的发展而变化。用拉伸搭接剪切试验方法估算的界面强度结果表明，由于界面处PP基体的较高结晶度和较大的球晶尺寸，通过减小热梯度可以大大提高界面剪切强度。另外，观察到混合结构的断裂机理随着热梯度的发展而变化。