Experimental study of notched tensile strength of large open-hole carbon fiber reinforced polymer laminates at low temperature

Carbon fiber reinforced polymer composites used in the aircraft structures often face the problems of open-hole and low temperature. A better understanding of the effects of low temperature and large open-hole on the tensile behaviors of carbon fiber reinforced polymer laminates is highly desirable. In this study the open-hole tensile tests on the carbon fiber/epoxy laminate-T700/SYE20005 with the stacking sequence of [0/90]4S were conducted at both room temperature and low temperature of −60 °C, where the specimens with three different ratios of hole diameter D over the specimen width W were considered. The results showed that the notched strength of the laminates decreases by 54.1% with the increase of the ratio D/W from 0.3 to 0.7 at room temperature. One interesting result is that low temperature greatly improves the strength of laminates with the ratios of D/W = 0.3 and 0.5, producing the increase of 13% in the notched strength, while it has an unobvious effect on the laminate with the ratio of D/W = 0.7. The observations of fracture surface of specimens show that the failure of the laminate with small open hole is mostly dominated by the fiber breakage and axial splits, and the interlaminar delamination and intralaminar matrix cracks are also found for the laminated specimen with large open hole.