Achieving excellent interfacial bonding of QP980 steel to CFRTP by laser joining via carbon fiber reinforced mechanical anchorage

Abstract

Carbon fiber reinforced thermoplastic composites (CFRTP)-metal hybrid structures can significantly reduce weight and cost while maintaining good performance. In this paper, a diode laser was used to join QP980 steel-CFRTP at a lap joint configuration. Furthermore, an ultrafast laser ablation process was used to produce periodic micro-groove structures on the surface of QP980 in order to generate mechanical anchors and improve QP980-CFRTP interfacial bonding performance. The relationship between the shear strength of QP980-CFRTP joints and laser heat input as well as QP980 surface micro-groove depth were evaluated. It was found that both heat input and micro-groove depth significantly affected the state of resin near the bonding interface. The suitable heat input and the micro-groove depth produced the optimized mechanical anchorage structures without the formation of the pores and porosities. Furthermore, a new method was proposed to significantly improve the joint performance where the orientation of fiber and the micro-grooves were intentionally designated as the same and perpendicular to loading direction in order to form carbon fiber reinforced interfacial mechanical anchorage structures. By optimized heat input, micro-groove depth and orientation, the peak load of the joint was dramatically improved by 515% compared with that without laser ablation treatment.