XFEM MODELLING OF SINGLE-LAP WOVEN FABRIC KENAF COMPOSITES BOLTED JOINTS WITH TEMPERATURE ACTION

Abstract The current paper aimed to model failures and fractures in single-lap bolted joints of woven fabric kenaf fiber reinforced polymer (KFRP) composite plate to fail in net-tension. The approach was based on the assumptions that micro-damage events were densely concentrated ahead of the notch tip and crack growth were readily seen along net-tension plane in a self-similar fashion. A 3-D finite element modelling framework were developed to explicitly incorporate bolt clamp-up in a range of KFRP series following tested experimental datasets. Lay-up types, normalized W/d, temperature exposure with constant bolt torque of 5 Nm were considered. It was found that KFRP plates under elevated temperature were stronger than under room temperature due to matrix toughening. Traction-separation relationship was incorported within Extended Finite Element Method (XFEM) framework to model damage within KFRP composite plate by using independent experimental datasets, here incorporates un-notched plate strength, σ o and fracture toughness, G c of all testing lay-ups. Constitutive model used is associated with stress concentration, therefore good agreement between predicted and experimental bearing stress at failure with net-tension failure mode is perhaps not suprising.

摘要 本研究旨在针对会发生净拉伸失效的机织红麻纤维增强聚合物（woven fabric kenaf fiber reinforced polymer, KFRP）复合板的单搭接螺栓连接，构建失效与断裂分析模型。本研究基于如下假设：缺口尖端前方区域密集聚集微损伤事件，且裂纹将沿净拉伸平面以自相似形式扩展。本研究搭建了三维有限元建模框架，可结合已有的实验数据集，对系列KFRP试件中的螺栓夹紧效应进行显式模拟。研究中考虑了铺层类型、归一化W/d比值，以及恒定5N·m螺栓扭矩条件下的温度暴露工况。研究结果表明，受基体增韧效应影响，高温环境下的KFRP复合板强度高于室温环境。本研究将牵引分离法则嵌入扩展有限元法（Extended Finite Element Method, XFEM）框架中，通过独立实验数据集对KFRP复合板内部的损伤进行建模，该数据集涵盖所有测试铺层的无缺口板强度σ_o与断裂韧性G_c。本研究所采用的本构模型与应力集中相关，因此净拉伸失效模式下，预测得到的失效支承应力与实验结果吻合良好，这一结果不足为奇。