Assembly of thermoplastic composites in the single strap joint configuration under bending

Thermoplastic composites are expected to play an important part in the aerospace material repairs, and one of the best examples is through use of the Single Strap Joint (SSJ), albeit the works related to the thermoplastic joints are not available. This study focuses on the co-cured SSJ with thermoplastic adherends under bending. The performance of the joints was investigated by flipping positions of the strap (strap-up and strap-down), with a particular focus on the capacity of the load as well as the applied displacements. The joint having a strap of 30 mm length was also numerically analyzed via an ABAQUS program. The results showed the joints with the strap-up were stronger than those with the strap-down because the strap remined mainly in normal compression stresses where the critical points existed, while for those with the strap-down, the strap suffered from peeling stresses in the same region. It was found that the strap-up joints are about 8% stronger and have about 26% higher displacements to failure, compared to the strap-down ones. Interlaminar delamination of the adherends or strap was observed as major failure mechanisms. Nevertheless, the failure zones for both cases were in tensile and/or shear out-of-plane stresses. The difference between experimental and numerical results of loads and applied displacements are about 9% and 2% for the strap-down joints, and about 8% and 4% for the strap-up joints, respectively. Simulations show the joint design could be improved for better performance.