Study on failure characteristics of fiber reinforced composite structural connections

In this paper, the three-dimensional progressive damage finite element models of composite bolted connection and adhesive-bolt hybrid connection were constructed, and the accuracy of the model is verified by comparing with the experimental results. The energy-based B-K criterion was used to simulate the damage and evolution of the adhesive layer, and the effects of bolt hole diameter, pre-tightening force and layup sequence on the failure characteristics of composite mechanical connections were analyzed. The results show that, in the bolted connection model, the final failure mode is typically extrusion damage near the bolt hole, with matrix failure being the primary form of failure. Appropriately increasing the diameter of the bolt hole or applying an appropriate pre-tightening force can both enhance the connection strength. Maximal strength of the connection structure is achieved when the first layer in the connection area is oriented at 0°, whereas if the first layer is oriented at 90°, the connection's bearing capacity is minimally reduced. In the adhesive-bolt hybrid connection model, the fiber and matrix damage of the four plies closest to the adhesive layer mainly spread along the 45°direction, and the damage is mainly matrix tensile damage.