Recently, a team of researcher Yang Shanglu from Shanghai Institute of Optics and Precision Machinery (SIPM) of the Chinese Academy of Sciences (CAS) has made new progress in laser-assisted joining of heterogeneous joints of metal-carbon fiber composites at the R&D Center of Laser Intelligent Manufacturing Technology. The team used a tunable flat-topped rectangular semiconductor laser as a heat source to realize the joining of high-strength steel and thermoplastic resin-based carbon fiber composites, elucidated the relationship between the interfacial thermal history of the heterogeneous materials, the interfacial shaping mechanism, and the joint performance, and put forward a new type of laser heat input process strategy. The related research results are summarized as "Effect of interfacial thermal history on bonding mechanism of laser assisted joining of QP980-CFRTP with adjustable flat-top rectangular laser beam", published in Composite Structures.
The development of high performance hybrid structures with multi-material systems is a growing trend in the aerospace industry. Carbon fiber reinforced thermoplastic composites (CFRTPs) have high specific strength and toughness, and can be hybridized with metals to satisfy both structural lightweighting and cost control requirements. Due to the huge difference in physicochemical properties between metals and composites, the existing methods of joining dissimilar materials are inadequate, and there is an urgent need to develop new joining processes with high quality and efficiency.
The team investigates the interfacial thermal history of the laser-assisted joining process, analyzes the temperature state of the resin matrix and its wetting behavior on the metal surface, and compares the effects of different interfacial thermal histories on interfacial joining defects, chemical compositions, joint strengths, and failure behaviors. Through the interfacial thermal history design method and laser thermal input process regulation, the limiting interfacial temperature and sufficient holding time are realized, which help the resin matrix to melt and diffuse completely on the metal surface, fill the micropores at the interface, and promote the chemical bonding, resulting in a high-quality joint with a peak load higher than 10 kN and a shear strength higher than 22 MPa. The related research results have a wide range of application prospects in aerospace and other related fields.
Figure 1. Laser-assisted joining process, ultrafast laser surface treatment structure and interface thermal history monitoring
Figure 2. Relationship between interfacial thermal history and resin wetting behavior on metal surface
