Bearing behaviors and failure mechanisms of 2D C/SiC plate with an open hole

Abstract

Since the interlaminar shear strength of 2D C/SiC composite is about one tenth of its tensile strength, design of 2D C/SiC mechanical joints should consider the influences of shear stress concentration around the open hole. The hole bearing performance becomes a key design parameter of 2D C/SiC plate. In this paper, drilling damages around the hole were evaluated by X-ray and infrared thermal wave method. The bearing interaction between the steel pin and the 2D C/SiC hole was then studied. Results show that the SiC matrix was peeled off during the hole-drilling process, and delamination damages were nonuniformly distributed around the hole. Four hole-bearing failure modes were found, such as bearing, crushing, net-tension and shear-off. The bearing stresses were 457.0 MPa for the bearing mode, 382.1 MPa for the crushing mode, 298.0 MPa for the net-tension mode, and 272.7 MPa for the shear-off mode. The failure modes became from net-tension to crushing as the increasing of the plate width under the condition that the regions around hole had the same density distribution. In addition, drilling damages around hole, such as delamination, nonuniform density distribution, peeled off matrix, and broken fibers, led to bearing and crushing modes occurred under the same geometry condition. It indicated that the hole was less likely to be crushed if the surrounded SiC matrix was much denser. Furthermore, the matrix cracking and the fiber bridging mechanisms control the hole-bearing behaviors. If the crack propagation was arrested by the fiber bridging mechanism, the bearing or crushing behaviors would occur. The longitudinal fiber tow near the woven pore seems to be fractured under the control of the microbuckling mechanism, which controls the continuously forming and removing process of the crushing damaged bulk material and determines the ductile crushing behavior and the elongation of the hole.