In situ analysis of interfacial damage in adhesively bonded composite joints subjected to various surface pretreatments

Secondary bonding of carbon fiber-reinforced polymer (CFRP) using structural adhesives is a promising technology. However, the joint performance can be ultimately affected by surface modifications attained through different surface preparation strategies. Thus, there is still a need for experimental techniques capable of assessing the mechanical properties associated with different surface preparations, and their relation to the damage morphology at initiation. In this work, a refined experimental set-up was used to perform three-point bending tests on miniaturized single-lap composite joints. Such testing configuration features a peel-dominant stress field within the bondline and the possibility to track the evolution of adhesive deformation and damage in situ at the meso-scale using optical microscopy. Epoxy-bonded CFRP joints were evaluated as a function of various surface pretreatments. In situ local observation obtained during mechanical loading provided insights into the detailed mechanisms taking place depending on the surface preparation strategies.