Experimental study on progressive failure mechanism of thin-laminate bolted joints

To understand the damage evolution and failure mechanism, the bolted joints of thin-ply laminated composites with single- and double-lap structures under quasi-static loading were studied experimentally. The specimens were observed using X-ray Microscopic Computerized Tomography (Micro-CT) scanning and Scanning Electron Microscope (SEM) imaging at special stages of the whole loading process to evaluate damage progression and deformation characteristics. The results show that the major failure modes of thin-ply laminates were found to be similar to those of conventional thick-ply laminates, including fiber breakage, matrix cracking, fiber kinking and fiber-matrix debonding. However, the major difference is that the common failure mode that has been reported in conventional thick-ply laminates, namely extensive delamination initiated from the bearing failure plane and tensile failure plane, was not seen in these thin-ply laminates due to the crack suppression ability of thin-ply prepreg. This ability allows the laminate to sustain additional bearing load and have higher damage tolerance. © 2021, Beihang University Aerospace Knowledge Press. All right reserved.