A combined experimental-numerical study of residual stress and its relaxation on laser shock peened SiC particle-reinforced 2009 aluminum metal matrix composites

Residual stresses have significant influences on the in-service performance of materials. Laser shock peening (LSP), a technique generating processing-based residual stress, is employed to introduce high-amplitude and large-depth compressive residual stress in SiC particle-reinforced 2009 aluminum (SiC/2009Al) metal matrix composites. Surface residual stresses after single-shot LSP and multiple shots of overlapped LSP were investigated. Single-shot LSP with 10 J, 20 J, 30 J, and 40 J laser energies introduced average surface residual stresses of −126.7 MPa, −129.3 MPa, −85.7 MPa, and −69.3 MPa. Multiple shots with energies of 20 J were inflicted twice on the surface undergoing LSP and exhibited a maximum residual compressive stress of −266.7 MPa. Then, the surface residual stress decreased from −266.7 MPa to −215.3 MPa and further to −212.7 MPa when subjected to 10,000 and 100,000 fatigue cycles. Relaxation also occurred under thermal loads, and the stress decreased from −266.7 MPa to −129.3 MPa after holding at 100 °C for 50 h. Furthermore, simulation of the LSP process was conducted with the SiC/2009Al composite and showed that SiC particles close to the peening surface generated more reverse plastic deformation and resulted in some residual tensile stress in their surroundings. This combined experimental and numerical research seeks to provide deep insight into residual stress distribution and explore the applicability of LSP with metal matrix composites.