Failure modes and failure mechanisms of single tooth bound to composite pre-tightened tooth connection

To assess the failure modes and failure mechanisms of single pre-tightened tooth connection joints, experiments were conducted on the mechanical properties of three different materials―T700/DER-321, T700/EP4221, and E-glass/HCH-8300―under different geometric parameters. During the test, failure processes and details of the fracture surfaces were observed by using a high-speed camera, an optical microscope, and a scanning electron microscope. Then, the failure modes and failure mechanisms of the joints were analyzed by numerical simulation and theoretical methods. The results showed that only two failure modes, shear failure and crushing failure, occurred in the glass fiber-reinforced plastic single joint. However, in addition to these two failure modes, a new failure mode was found to occur in the carbon fiber-reinforced plastic single joint, i.e. compression failure. The glass fiber-reinforced plastic joint had a lower elastic modulus along the fiber direction than the carbon fiber-reinforced plastic joint, which was the fundamental cause for the new failure mode. The carbon fiber-reinforced plastic joint with compression failure had a higher bearing capacity, and a certain ductile failure will occur as a result of the large interlaminar shear strength of the composite, which is an important consideration in joint design. Thus, the material type, the geometrical parameters of the tooth, and the interlaminar shear strength of the composite all influenced the failure modes and the bearing capacity of single pre-tightened tooth connection joints.