Effects of impact fatigue on residual static strength of adhesively bonded joints

Abstract

In most industrial applications, adhesive joints experience impact fatigue loads in service. The energy of each impact is too low to cause joint failure. Although the repetitive impacts usually do not apparently affect the joints, they can significantly reduce the strength of adhesively bonded structures. Accordingly, understanding the effect of impact fatigue on the residual strength of the bonded components is crucial in real applications. This study deals with this issue where the effect of impact fatigue on the residual static strength of single lap joints is analyzed. To achieve this, the manufactured single lap joints were categorized into four different groups. Group 1 joints were tested under static loading conditions. Joints in group 2 were tested under impact to obtain the impact strength of the single lap joints. To analyze the impact fatigue life of the joints, the single lap joints in group 3 were tested under cyclic impact at different energy levels until failure. To investigate the effect of impact fatigue on the residual static strength of the joints, single lap joints in group 4 were tested under a specific number of impact cycles followed by a static tensile test. Using microscopic analysis, the fracture surfaces of the tested specimens were analyzed. The results showed that cracks initiate from the middle of the bonded area as a result of cyclic impact stress waves. Then, by increasing the number of impacts, a large number of cracks nucleate from the edges of the joints and grow along the width to the middle of the overlap. A 3D finite element method was employed to analyze the stress distribution along the bondline under impact loads.

Sustainable Development Approaches through Wooden Adhesive Joints Design

“…Structures can suffer premature failure over time if long-term cyclic loads accumulate at stresses below the static strength of the material [ 115 ]. Wooden structures are highly susceptible to fatigue loading.…”

Impact fatigue life improvement of bonded structures using the bi‐adhesive technique

“…In this section, the low cycle impact fatigue life of the joints was analyzed by an in-house designed drop weight impact test machine. 16 Using the impact fatigue machine, the maximum capacity of the impactor at hit is 50 N.m. The specimens were subjected to different impact energy levels due to their impact strength.…”

“…The damage of adhesively bonded SLJs subjected to three‐point bending low energy impacts and impact fatigue was experimentally and numerically investigated by Huang et al 15 They proved that the residual strength of the joints decreases by the increase of impact energy. Jalali et al 16 experimentally investigated the reduction of static strength as a result of low energy impact fatigue loads. They measured the residual static strength of the SLJs after enduring specific cycles of low energy impacts.…”

Fatigue analysis of 7075-T6 aluminum alloy under high compressive residual stresses by considering the non-propagating crack region

“…Numerous methods have been developed to control, postpone, and decrease this unfavorable effect, such as cold expansion, [1][2][3][4][5] bolt clamping, 6 interference fit method, 7 and adhesively bonded joints. 8,9 The cold expansion process causes a compressive residual stress field at the periphery of the hole which reduces the resultant stress and delays the initiation and propagation of fatigue cracks and prolongs the fatigue life. The compressive residual stress is caused by passing an oversized conical mandrel through the hole in the cold expansion process (Figure 1).…”