Abstract
The adhesive joint of composite materials is one of the typical structures in aircraft structures, and the delamination damage is one of the most important damage modes in composite adhesive joints. In this paper, static and fatigue tests were carried out on L-shaped adhesive joints to analyze the damage evolution and failure modes of delamination damage under static and fatigue loadings. Based on the cohesive constitutive models, the static and high-cycle fatigue delamination constitutive models were developed. The static and fatigue numerical models of composite L-shaped adhesive joints were established by using finite element software. The stress distribution, deformation modes and delamination propagation laws were systematically studied. The simulation results are in good agreement with the experimental results. The delamination damage initiation, evolution and failure mechanism of L-shaped adhesive joints under static and fatigue loads were revealed by combining the experimental and the numerical results, which will provide theoretical and engineering guidance for strength and fatigue analysis of composite adhesive structures.
Highlights
本文以复合材料 L 型胶接接头为研究对象,进 行静力和疲劳试验,发展了基于内聚力单元的静力 和高周疲劳分层扩展模型,改进疲劳分层扩展中能 量释放率的计算方法,提高其计算精度,结合试验和 数值结果,系统研究了 L 型胶接接头的分层损伤扩 展和失效机理。
Study on delamination damage evolution of composite L⁃shaped adhesive joint based on cohesive behavior
The static and fatigue numerical models of com⁃ posite L⁃shaped adhesive joints were established by using finite element software
Summary
本文以复合材料 L 型胶接接头为研究对象,进 行静力和疲劳试验,发展了基于内聚力单元的静力 和高周疲劳分层扩展模型,改进疲劳分层扩展中能 量释放率的计算方法,提高其计算精度,结合试验和 数值结果,系统研究了 L 型胶接接头的分层损伤扩 展和失效机理。 复合材料 L 型胶接接头采用二次胶接连接,首 先将 L 型加强筋和底板固化成型,再使用 Loctite 胶实现加强片和底板的胶接, 胶层名义厚度为 0.12 mm,试验件几何尺寸如图 1 所示,复合材料体 系为 T300 / CYCOM 970, 预浸料单层名义厚度为 0.25 mm,L 型加强筋的铺层为[ - 45 / 0 / 45 / 90] s,底 板复合材料的铺层顺序为[ -45 / 0 / 45 / 0 / -45 / 0 / 90 / 0 / -45 / 0] s,底板两侧和 L 型板上端采用加强片加 强,加强片长度为 40 mm,厚度为 2 mm,试验件宽度 为 60 mm,静力试验采用 INSTRON 8872 电液伺服 试验机,静力试验的控制方式为位移控制,加载速率 为0.5 mm / min,为了减少试验结果的分散性, 静力 试验包含 3 件试样,试验过程中在试验件 VL、VR 和 PL 3 个位置布置应变片,其中 PL 位置为 L 型下端 面的中心线位置,距 A 端 12.5 mm,VL 和 VR 对称贴 片,距 B 点 10 mm。 3.1 静力分层数值模型 基于 ABAQUS / EXPLICIT 模块建立复合材料 L 图 13 给出了 L 型胶接试验件在不同疲劳阶段 的分层扩展情况及裂尖应力集中分布,选取 L 型板 和底板的连接区域进行局部放大。 可以观察到,疲 劳裂纹扩展前,L 型板在圆弧过渡区域存在应力集 中,Mises 应力较大,导致了较高的能量释放率,故首 先产生局部分层,随着疲劳损伤的不断累积,分层损 伤不断向前扩展,且分层裂纹尖端的应力较高,进一 步促进分层损伤的扩展,分层区域迅速贯穿整个搭 接区域,胶接接头丧失承载能力并发生疲劳破坏。
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