Impact damage and low temperature effects on carbon fiber/epoxy joints: A comparative study of hybrid bolted/bonded and bolted configurations with cross-ply and angle-ply laminates

This study investigates the tensile and tensile after impact (TAI) performance of hybrid bolted/bonded (HBB) and only bolted (OB) carbon fiber/epoxy composite joints with cross-ply (CP) and angle-ply (AP) stacking sequences under low-temperature (LT) conditions. The focus is on the behavior of these joints under low temperatures with barely visible impact damage (BVID), relevant to aerospace and high-performance industries. In situ acoustic emission (AE) analysis and fractographic examinations synergistically evaluate the effects of LT (−55 °C) and BVID (10 J energy level) on these joints. Results indicate that HBB-CP intact joints exhibit higher load-bearing capacity at LT due to increased adhesive and matrix stiffness but demonstrate more brittle responses. The combined impact of low temperature and impact loading significantly affects impacted CP joints, leading to notable damage and reduced load-bearing capacity. Although HBB-CP joints are more susceptible to BVID than OB-CP joints, they still outperform overall. AE and fractographic analyses reveal fiber-related failures in CP laminates and matrix/interface failures in AP laminates, with increased matrix cracking at low temperatures. This research provides a comprehensive analysis of the interplay between impact dynamics, temperature variations, and stacking sequence configurations on hybrid and bolted composite joints.