Investigation of analysis and improvement of the assessment of bonding performance for thermoplastic composites

A lap shear test is employed to evaluate the interfacial bonding strength between unidirectional CF/PEEK tapes as quantification of bonding quality. In this study, a novel tab is proposed to ameliorate bonding testing. The crucial role of developed tabs is to avoid the adherend fracture that is typically observed in specimens with conventional tabs. Specimens with different tab, bonding processes, and lap lengths are prepared and tested. Moreover, theoretical analysis is conducted to predict bonding strength, and finite element simulations are also performed for stress distribution in these specimens with different types of tabs. The experimental and theoretical results demonstrate that the full tab is employed in the bonding test, the stress concentration reduces nearly by 6 times, and the failure mode coincides with the expected requirement. Additionally, the highest estimation of bonding strength increases nearly by 69%, and is approximately consistent with the theoretical calculation, up to 98.6%. This tab configuration, with low dependence on processes and joint parameters, describes a straightforward and efficient procedure to meliorate the quantification of the bonding strength, and is found to be applicable in the tape placement process and single-lap-joint assemblies for thermoplastic composites.