On sequential ultrasonic spot welding as an alternative to mechanical fastening in thermoplastic composite assemblies

Abstract

In previous work, single-spot ultrasonically welded joints were found to feature similar load carrying capability in shear but significantly low capability in peel as joints with a representative single-mechanical fastener. This leads to questioning welding as an appropriate solution for the commonly-used single-lap joint configuration. The present paper investigates the mechanical performance of spot welded single-lap joints in thermoplastic composites in comparison to their mechanically fastened counterparts. Single-row joints, double-row joints with varying inter-row distance and multi-row joints with varying number of rows were investigated in this study. The results showed that, owing to higher joint stiffness and hence lower secondary bending and peel stresses, the load carrying capability of the spot welded joints was comparable to that of the mechanically fastened joints in all considered cases. Likewise, the effects of increasing the inter-row distance and of increasing the number of rows were similar for both types of the joints.