Chen Guangchang, Zhang Jindong, Liu Gang, Chen Puhui, Guo Miaocai
State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
National Key Laboratory of Advanced Composites, AVIC Composite Technology Center, Beijing 101300, China.
Polymers (Basel). 2019 Jul 30;11(8):1260. doi: 10.3390/polym11081260.
This study investigated the effect of the fusion-bonded dots of veil interleaves on the crack propagation path of the interlaminar fracture of continuous carbon fiber reinforced epoxy resin. Two thin fiber layers (i.e., nylon veil (NV) with fusion-bonded dots and Kevlar veil (KV) physically stacked by fibers) were used to toughen composites as interleaves. Result shows that the existence of fusion-bonded dots strongly influenced the crack propagation and changed the interlaminar fracture mechanism. The Mode I fracture path of the nylon veil interleaved composite (NVIC) could propagate in the plane where the dots were located, whereas the path of the Kevlar veil interleaved composite (KVIC) randomly deflected inside the interlayer without the pre-cracking of the dots. The improvement of Mode I toughness was mainly based on fiber bridging and the resulting fiber breakage and pull-out. Fiber breakage was often observed for NVIC, whereas fiber pull-out was the main mechanism for KVIC. For the Mode II fracture path, the fusion-bonded NV dots guided the fracture path largely deflected inside the interlayer, causing the breakage of tough nylon fibers. The fracture path of the physically stacked KVIC occurred at one carbon ply/interlayer interface and only slightly deflected at fiber overlapped regions. Moreover, the fiber pull-out was often observed.
本研究调查了面纱夹层的热熔粘结点对连续碳纤维增强环氧树脂层间断裂裂纹扩展路径的影响。使用两层薄纤维层（即带有热熔粘结点的尼龙面纱（NV）和通过纤维物理堆叠的凯夫拉尔面纱（KV））作为夹层来增韧复合材料。结果表明，热熔粘结点的存在强烈影响裂纹扩展并改变层间断裂机制。尼龙面纱夹层复合材料（NVIC）的I型断裂路径可在点所在平面内扩展，而凯夫拉尔面纱夹层复合材料（KVIC）的路径在层间随机偏转，且点无预开裂。I型韧性的提高主要基于纤维桥接以及由此产生的纤维断裂和拔出。在NVIC中经常观察到纤维断裂，而纤维拔出是KVIC的主要机制。对于II型断裂路径，热熔粘结的NV点引导断裂路径在层间大幅偏转，导致坚韧的尼龙纤维断裂。物理堆叠的KVIC的断裂路径发生在一个碳层/层间界面处，并且仅在纤维重叠区域略有偏转。此外，经常观察到纤维拔出。
