Effect of joint flexibility in adhesively bonded composite panel-to-flange joints

Abstract

An experimental and numerical study was conducted to investigate the postbuckling induced failure in adhesively bonded composite postbuckled panel-to-flange (ABPTF) joints. Each ABPTF joint structure consists of two laminated flanges bonded to a long laminated panel. When the ABPTF joint structure is loaded in compression, the long panel buckles and then generates a relatively large peel stress in the joints. To understand the effects of joint flexibility on the buckling load, failure load and the failure mechanism, a variety of specimens were manufactured using two different stacking sequences for the long panel lay-up, i.e. ( ± 45/0/90)s and (0/90/ ± 45)s, and seven different stacking sequences for the flange lay-up, i.e. ( ± 45/0/90)2s, ( ± 45/0/90)s, ( ± 45)s, ( ± 45)2s, (0/90/ ± 45)2s, (0/90/ ± 45)s and (0/90)s. Typical buckling and postbuckling behaviour for all specimens was observed and then correlated with the numerical predictions. The failure surfaces were studied using a scanning electron microscope (SEM), and features of failure were identified. It is revealed that flexible joints have reduced peel stress and consequently provide higher joint efficiency while stiff joints have relatively large peel stress and thus give lower joint efficiency. Here joint efficiency is defined as the ratio of the maximum stress outside joint to its associated strength allowable when joint fails.