Efficient manufacturing techniques and connection failure analysis of CFRP lifting lug for main bearing structure

Abstract

Complex lifting lug connection structures often hinder the integral molding of main load-bearing components in automotive, aerospace, construction, and other fields, thus limiting the potential for lightweight structural design. In this paper, a method of forming web-reinforced sandwich composite lifting lug structure of the new energy vehicle by thermal expansion molding process (TEMP) is proposed, and connection failure analysis model is established to verify the process-structure-performance relationship. First, compression tests and failure analysis confirmed that the web-reinforced structure significantly improved the strength and stiffness of the lifting lugs. Then, the hybrid connection mode of the steel sleeve through the thermal expansion film and glass fiber reinforced plastics (GFRP) was designed, and the reliability of the steel sleeve interface connection was verified by the axial press out test. Finally, the lifting lug was simulated to be mounted on the vehicle body, and the comprehensive connection performance was verified by connection compression test, finite element analysis (FEA) and macroscopic failure mode. This study determined that the web-reinforced structure increased the initial failure load of the lifting lug by 65%, surpassing 60 kN compared to the pure foam sandwich structure. The maximum pressure load of the steel sleeve reaches 11.24 kN, and the comprehensive connection strength can meet the static load of the battery box more than 6000 kg. The TEMP technology has the potential to integrate and scale up main bearing components with complex web reinforcement structures.