Effects of bondline thickness on Mode-II interfacial laws of bonded laminated composite plate

Abstract

For a variety of modern industries, interfacial delamination is a critical issue for the design and application of laminated composite structures. Numerous global experimental studies have been conducted to characterize the toughness of adhesively bonded composite structures. In the recent two decades, cohesive zone models (CZMs) have been receiving intensive attentions. The local interfacial traction-separation laws as the fundamental input are crucial for the successful applications of CZMs. Several local tests have also been conducted to determine the interfacial traction-separation laws in adhesively bonded joints. However, very few tests have been employed to investigate the dependency of the local interfacial traction-separation laws on the bondline thickness, particularly, for the laminated composite joints under Mode-II loading conditions. In this work, the effects of bondline thickness on the interfacial behavior have been systematically investigated at various typical bondline thicknesses (from 0.1 to 0.8 mm). The effects of adhesive thickness on the interfacial toughness, interfacial strength, and shapes of the local interfacial traction-separation laws have also been evaluated. The test results indicated that the measured Mode-II (shear test) interfacial

Influence of adhesive thickness on local interface fracture and overall strength of metallic adhesive bonding structures

“…The aforementioned crack is actually created due to the failed and disappeared CZ elements. And the separation strength is therefore substantially affected by various adhesive thicknesses, which is confirmed by numerous previous researches [18][19][20][21].…”

“…In other words, with the increasing adhesive thickness, both of the two separation displacements would increase. Furthermore, the previous experimental investigations on the CZM influenced by adhesive thickness have shown the critical separation ratio d c =d f seems approximately unchanged [18][19][20]. Based on these considerations, the present investigation supposes the critical separation ratio l is independent of adhesive thickness.…”

“…However, the separation strength would be identical to the bulk fracture strength s f when the adhesive thickness increases to a certain critical value, which has been pointed out by numerous experimental observations [2,5,[18][19][20]. In the present study, the critical value of adhesive thickness is termed critical thickness and denoted by t c and the corresponding initial stiffness is k 0c , Thus l could be rewritten by combining Eqs.…”

“…The separation strength of the adhesive layer could be treated as an equivalent local strength and would be hence influenced by adhesive thickness, which has been confirmed by some previous experimental studies. Ji et al [18][19][20] carried out a series of experiments to investigate the influence of adhesive thickness on the single mode and mixed-mode cohesive laws. It was observed that adhesive thickness had a substantial impact on both the fracture energy and the separation strength.…”

Predicting the strength of adhesively bonded joints of variable thickness using a cohesive element approach

“…This method was proposed by [26][27][28] and extended for composite bonded joints by Fernandes et al [29]. The cohesive law is characterised through the differentiation of the relationship between the fracture energy, J II , and the crack opening displacement in mode II.…”