Effect of Z-fibres™ on the delamination behaviour of carbon-fibre/epoxy laminates
Effect of Z-fibres™ on the delamination behaviour of carbon-fibre/epoxy laminates
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发表时间：
2000-12
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通讯作者：
D. Cartié
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作者：
D. Cartié
本论文提出的研究调查了Z形钉扎层合板在不同分层断裂载荷条件下实验确定的行为与其细观结构之间的关系，在IMS/924层合板的Z纤维增强单向梁上进行了模式I、模式II和混合模式1/11分层断裂测试对于模式I载荷下的双悬臂梁试件（DCB），梁的裂纹扩展阻力随着钉扎密度的增加而增强。与本研究中使用的直径和 PMNG 密度相比，承载能力提高了多达 5 倍，表观韧性提高了多达 20 倍。ZFibreTM 钉扎有效性的最值得注意的例子是在本质上不稳定的 3pt-ENF 配置中的 II 型载荷条件下稳定分层裂纹扩展。尽管当前基于 LEFM 的数据分析包含在计算分层韧性值的测试协议中，但由于然而，这些数据简化方法不允许直接量化不同钉扎参数对全厚度钢筋裂纹桥接能力的影响。有限元方法，利用这些实验确定的单销桥接定律，作为一种工具，对销长度、直径和位置对分层梁行为的影响进行参数化研究。模拟和实验 R 曲线之间的良好一致性表明，DCB 样本的 I 型分层行为与单销拉拔牵引定律有关。最后，ZFibreTh 增强层合板冲击后压缩行为的初步研究表明存在材料的分层裂纹扩展阻力的显着增强与其冲击后压缩性能的最终改善要低得多（最多 50%）之间存在复杂的关系
The study presented in this thesis investigates the relationship between the experimentally determined behaviour of Z-pinned laminates under various delamination fracture loading conditions and their mesostructure Mode I, mode II and mixed mode 1/11 delamination fracture testing was carned out on Z-Fibre reinforced unidirectional beams of IMS/924 laminates For the Double Cantilever Beam specimens (DCB) under mode I loading, the crack propagation resistance of the beam is enhanced with increased pinning density For the range of pin diameters and pmmng densities used for this study, the load carrying capability has been improved by up to 5 times and the apparent toughness has been improved by up to 20 times The most noteworthy example of the effectiveness of ZFibreTM pinning is the stabilisation of delamination crack propagation under mode II loading conditions in the intrinsically unstable 3pt-ENF configuration Although the current data analyses, based on LEFM, included in the test protocols for the calculation of delamination toughness values are invalidated by the presence of the through-thethickness reinforcement, they are used here as the best currently available means of normalising the fracture results However, these data reduction methods do not allow direct quantification of effects of the different pinning parameters on the crack bridging capability of the through-thethickness reinforcement In order to relate the micromechanics at the pin level with the Mesomechanics of the delamination fracture specimens, the determination of the traction laws of a single Z-Fibre, bridging a crack and deformmg under various loading conditions, have been determined successfully by single pin experiments A finite element approach, utilising these experimentally determined single pin bridging laws, is presented as a tool to cany out parametric studies of the effects of pin length, diameter and location on the behaviour of delaminating beams The good agreement between the simulated and experimental R-curves demonstrates that the mode I delamination behaviour of DCB specimens is related to the single pin pullout traction laws Finally, preliminary studies of the compression after impact behaviour of ZFibreTh reinforced laminates indicate the existence of a complex relationship between the dramatic enhancement of the delamination crack propagation resistance of a material and the much lower (up to 50%) ultimate improvement in its compression after impact performance