Mechanical behavior and failure characteristics of fir-tree tenon joint structures based on numerical simulation

To address bottlenecks such as stress concentration and poor detachability in carbon fiber reinforced polymer (CFRP) connectors, this study proposes a bio-inspired multi-level interlocking fir-tree joint, integrating aero-engine mechanisms with ironclad beetle elytra microstructures. Through quasi-static tensile tests and nonlinear finite element analysis (FEA) using the Hashin criterion, the stress transfer mechanisms and progressive failure behavior were investigated. Results show that the peak load of the fir-tree joint is 111% and 308% higher than those of the traditional square-head and dovetail joints, respectively. Response surface analysis (RSA) clarified the effects of wedge angle, top/bottom flank angles, and tooth pitch, validating the analytical model with a minimum error of 0.1%. Additionally, a bio-inspired fiber orientation strategy optimized the interlaminar stress distribution and improved structural stiffness. This research provides a novel structure-function approach for high-performance detachable composite connectors, offering valuable optimization criteria for aerospace and structural engineering.