Evaluation of Interlaminar Stresses in Composite Laminates with a Bolt-Filled Hole Using a Linear Elastic Traction-Separation Description

Yong Cao,Xiaofeng Xue,Yunwen Feng,Wenzhi Wang,Liang Bai

doi:10.3390/app7010093

Abstract

Determination of the local interlaminar stress distribution in a laminate with a bolt-filled hole is helpful for optimal bolted joint design, due to the three-dimensional (3D) nature of the stress field near the bolt hole. A new interlaminar stress distribution phenomenon induced by the bolt-head and clamp-up load, which occurs in a filled-hole composite laminate, is investigated. In order to efficiently evaluate interlaminar stresses under the complex boundary condition, a calculation strategy that using zero-thickness cohesive interface element is presented and validated. The interface element is based on a linear elastic traction-separation description. It is found that the interlaminar stress concentrations occur at the hole edge, as well as the interior of the laminate near the periphery of the bolt head. In addition, the interlaminar stresses near the periphery of the bolt head increased with an increase in the clamp-up load, and the interlaminar normal and shear stresses are not at the same circular position. Therefore, the clamp-up load cannot improve the interlaminar stress distribution in the laminate near the periphery of the bolt head, although it can reduce the magnitude of the interlaminar shear stress at the hole edge. Thus, the interlaminar stress distribution phenomena may lead to delamination initiation in the laminate near the periphery of the bolt head, and should be considered in composite bolted joint design.

Highlights

Interlaminar stresses can lead to damage in the form of delamination and matrix cracking of laminate, especially at the free-edges of a laminate [1,2]
The interlaminar stress distribution characteristics of filled-hole compression tests can be identified by the failure mode
They supposed that the reason for the filled-hole compression (FHC) test, and observed that the crack initiated at the periphery of the this phenomenon was that the tightening modified the local triaxial stress concentration and load bolt with a little off-setthe from high 0◦ oriented lay-ups, trend and the final failure mode transfer between holethe andnet the section bolt

Summary

Introduction

Interlaminar stresses can lead to damage in the form of delamination and matrix cracking of laminate, especially at the free-edges of a laminate [1,2]. Accurate and proper design of bolted composite joints requires the determination of the local stress field within the laminate [3]. The stress field in the vicinity of a bolt hole is generally considered to be three-dimensional (3D) [4,5,6]. It is important to take interlaminar stresses into account in composite bolted joint design. Due to various kinds of bolted composite joints, a filled-hole laminate was used as a means to characterize the stress distribution of bolted joints in this paper. Filled-hole strength has been widely used to generate design data to establish allowables for composite bolted joint analysis [7]

Results

Discussion

Conclusion