Analysis of automotive mixed-adhesive joints weakened by moist conditions: Experimental characterization and numerical simulation using cohesive zone model

This paper is mostly concerned with an experimental and numerical study to clarify the behaviour and failure in the mono-adhesive joints and mixed-adhesive joints under different environmental conditions (dry [E-0], 75.3% relative humidity [E-1], 84.2% relative humidity [E-2], and submerged in tap water [E-3] at 25 degrees C) and different strain rates (1 and 100 mm/min). Experimental investigations are compared with the numerical analysis, which is carried out by bilinear cohesive zone model (CZM). Through this work, degradations of cohesive parameters are calculated by using open-faced double cantilever beam (DCB) and end notch flexure (ENF) specimens. The experimental data show that the cohesive parameters of Araldite 2015 have negative correlation to moisture content. Although Araldite AV138 parameters experience a decrease in mode I, in mode II, its cohesive parameter increases. First, it is found that the decrease in experimental failure load of mixed-adhesive joints with regard to the dry condition is recorded as 32.6%, 54%, and 59.1% for E-1, E-2, and E-3 conditions, respectively. Following this further, single lap joint (SLJ) that has non-uniform moisture content distribution is modelled by engaging specific CZM parameters related to the specific moisture content. The results show a good agreement between experimental and numerical data.