Drilling-induced delamination effect on the bending and out-of-plane shear characteristics of the woven carbon/epoxy composites

The drilling process of laminated composites presents significant challenges in control and frequently results in delamination. As one of the most critical forms of damage, drilling-induced delamination has become a prominent research focus due to its considerable engineering significance. This phenomenon notably impacts the structural integrity of composite materials when subjected to various loading conditions. Among the mechanical properties influenced by drilling-induced delamination, the load-carrying capacity (LCC) of specimens under bending and shear forces has received limited scholarly attention. The present research investigated the impact of drilling-induced delamination on the open-hole (OH) bending and out-of-plane shear characteristics of carbon/epoxy composites. A series of hole-making scenarios were carried out to achieve the minimal and maximal dimensions of delamination. A broad series of mechanical tests were performed using redesigned symmetrical and anti-symmetrical four-point bend test (4PBT) procedures on the OH samples. Utilizing the test configuration, the OH samples were subjected to pure bending (PB), reverse pure bending (RB), and out-of-plane shear (OS) loads. The results showed that drilling-induced delamination, with a typical dimension surrounding the hole with a ratio of hole diameter to width ( d / w ) of 0.19, can reduce the LCC of OH samples subjected to PB, RB, and OS loads by approximately 2.4, 5, and 1.1%, respectively. In cases where the delamination dimension increases, the LCC of the samples decreases more.