Laser Joining of CFRTS and Steel by Interfacial Pressure Control

Abstract

The carbon fiber-reinforced polymer (CFRP) metal structure is widely used in various industries to reduce the weight and cost of the structure without compromising performance. The main challenge for manufacturing the CFRP metal structure comes from the lack of flexible and robust joining processes. In this study, a new laser joining process was developed that used a thin layer of polyamide 6 as an interlayer material lying between carbon fiber-reinforced thermosets and a quenching-partition (QP) 980 steel to achieve the joint since the laser can’t directly join the steel to the thermoset composite. It was found that the joint’s strength was seriously degraded by the porosity’s formation. The porosity formation mechanism was studied by online-recording the thermal history inside the joint during the laser joining process. Experimental results demonstrated that the emerging of the porosities in the joint was mainly caused by the cooling shrinkage instead of pyrolysis gas release. Furthermore, a new approach of controlling and optimizing the interfacial pressure was developed to suppress the porosity formation in the joint, which can significantly reduce the porosity rate from 25.8 to 1.2% and dramatically improve the joint shear strength from 10.69 to 18.6 MPa by 73.99%.