Effect of overlap length on tensile properties and failure characteristics of CFRP single-lap adhesive joints

The single-lap joints with different overlap lengths were bonded by carbon fiber reinforced plastics (CFRP) laminate, and their failure load, fracture process and strain fields were characterized by digital image correlation (DIC) and universal testing machine. The effects of overlap length on the tensile properties, fracture process, strain distribution and failure characteristics of single lap joints were studied. The results show that with the development of overlap length, the average shear strength of joints is decreased firstly and then tends to be stable. The secondary bending effect of joints caused by the eccentric load during the stretching process becomes more significant with the increase of overlap length, the end deformation of the lap area is increased, and the initial failure position of joints changes from one end to both ends of the lap area. The strain concentration area at the end of the front and side of joints transitions from asymmetric to symmetric. The peeling stress of joints gradually is increased, and the main failure mode between layers is changed from shear to peeling failure. The failure mode of joints go through the process from interface and slight fiber tearing to mixed failure and then to delamination.