Numerical Analysis of Bending Properties of a Novel Composite Bolted T-joint with Internal Laminate Skeleton and External Skin

The composite bolted T-joint, consisting of internal laminate skeleton and external skin, presents substantial potential for replacing aluminum alloys as the primary load-carrying connection structure. However, its complex failure mechanisms and numerous design parameters pose challenges for engineering applications. To identify critical design parameters significantly impacting its bending performances, a validated finite element model of this T-joint under bending loads was established. Using uniform design and multiple linear regression methods, the significance of 15 design parameters related to machining, configuration, and resin properties on bending performances was systematically investigated and the effect mechanisms of certain parameters were discussed. The results show that parameters such as the base panel bolt hole radius (r_B), corner radius (r_C), the thickness of the upper surface skin (t_U), base panel skeleton (t_{S_B}), and lug skeleton (t_{S_L}) have significant positive effects. Failure of the resin area between the skin and skeleton results in localized weak stress area in the skin, thereby reducing the overall load-carrying capacity of the joint. r_B has an optimal value that balances bending performances and fastener weight. The final failure location of the joint is either in the base panel skeleton or lug skeleton, depending on the relative thickness of each. Additionally, when designing composite T-joints with multiple configuration components for primary load-carrying connections, it is advisable to place weak load-carrying positions away from the load-carrying core.