The Effect of Metal on Composites Fatigue Damage in Mixed Structure

混合结构中金属疲劳对层合板损伤的影响

¹ School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China
² First Aircraft Institute of AVIC, Xi'an 710089, China

Received: 12 March 2017

Abstract

This paper investigated the fatigue damage coupling of composite laminate and metallic plate in multi-bolt joint. A progressive fatigue damage model for composite laminates and a modified Lemaitre damage model for metal material were developed. A phenomenological elastoplastic constitutive model was used to describe the in-plane shear nonlinearity of composite lamina. A formula for calculating the energy release rate of the low cycle fatigue was derived based on spherical tensor and shear tensor decomposition of the stress. The developed models were validated by the experimental results of a double-lap single-bolt metal-composite joint and were employed to simulate the fatigue damage of a double-lap, multi-bolt metal-composite joint. The result indicates that fatigue damage will harden the materials nearby the bolt region of the metallic plate for a multi-bolt joint structure when suffering to cyclic loads. This hardening behavior results to a transfer of bolt loads towards the harden region, which intensifies bearing damage and reduces tensile stress in the composite laminate, and improves the fatigue life of composite laminates fail in tensile mode.

摘要

针对混合结构中层合板和金属的疲劳损伤耦合问题，构建了复合材料渐进疲劳损伤模型和金属材料Lemaitre疲劳损伤模型，采用唯象的弹塑性本构描述单层复合材料面内剪切非线性，基于球张量和剪切张量的应力分解方法推导了低周疲劳能量释放率计算公式。对单钉与多钉螺栓连接结构进行了疲劳损伤和寿命分析，结论表明：循环加载过程中，多钉连接结构钉载向金属搭接板疲劳硬化区域迁移，加剧了层合板局部挤压损伤，降低了层合板拉断载荷，有利于提高以拉断为破坏模式的层合板疲劳寿命。