Strength and Failure Mechanism of Composite-Steel Adhesive Bond Single Lap Joints

Kai Wei,Yiwei Chen,Xujing Yang,Maojun Li

doi:10.1155/2018/5810180

Abstract

Carbon fiber-reinforced plastics- (CFRP-) steel single lap joints with regard to tensile loading with two levels of adhesives and four levels of overlap lengths were experimentally analyzed and numerically simulated. Both joint strength and failure mechanism were found to be highly dependent on adhesive type and overlap length. Joints with 7779 structural adhesive were more ductile and produced about 2-3 kN higher failure load than MA830 structural adhesive. Failure load with the two adhesives increased about 147 N and 176 N, respectively, with increasing 1 mm of the overlap length. Cohesion failure was observed in both types of adhesive joints. As the overlap length increased, interface failure appeared solely on the edge of the overlap in 7779 adhesive joints. Finite element analysis (FEA) results revealed that peel and shear stress distributions were nonuniform, which were less severe as overlap length increased. Severe stress concentration was observed on the overlap edge, and shear failure of the adhesive was the main reason for the adhesive failure.

Highlights

With the aim to save energy and reduce emission, weight saving is of significant importance in the transportation industry
The key problem is that high stress concentrations can develop around the fastener holes, and the joint can be brought to failure at far lower stress levels than expected [4]
Due to its larger bond area to distribute loads and eliminate stress concentration as well as keeping structure integrity, adhesive bonding is more attractive as compared to mechanical fastening joining methods [5]

Summary

Introduction

With the aim to save energy and reduce emission, weight saving is of significant importance in the transportation industry. E commonly used methods for joining composite parts are either through mechanical fastening or bonding. Due to its larger bond area to distribute loads and eliminate stress concentration as well as keeping structure integrity, adhesive bonding is more attractive as compared to mechanical fastening joining methods [5]. Extensive researches have been conducted to investigate the bonded joints through analytical, experimental, and numerical methods. Previous researches focused on different affecting factors on the joint strength and damage mechanism [6,7,8,9,10]. E present study mainly focused on the mechanical properties and failure behavior of CFRP-to-steel adhesively bonded single lap joints. Mechanical properties were firstly shown and compared with each other Both the experimental and numerical results about joint strength were displayed for further detailed analysis. Photographs of the failure joints were exhibited for failure mode analysis

Experiments

Finite Element Analysis

Results and Discussion