Model fatigue crack propagation for unidirectional carbon fiber/epoxy laminates in liquid nitrogen

摘要

For commercial composite laminates, it is rather difficult to change the properties of resin only. One of the way to achieve this condition is to change the test temperature because only the resin properties are sensitive to temperature. Mode I fatigue crack propagation behavior were investigated with unidirectional carbon fiber (CF)/epoxy laminates, HTA/l13 and their neat resin, No.113, in liquid nitrogen at 77K, respectively using double cantilever beam and compact tension specimens. In our previous study, mode I interlaminar fracture toughness values of HTA/113 laminates at 77K were about 1.1 times as large as those at RT. Mode I fracture toughness values of epoxy No.113 at 77K were about 3.8 times as large as those at RT. In this study, mode I fatigue crack propagation behavior were investigated with the same materials. The fatigue crack growth resistance of HTA/113 laminates at 77K was higher than that at RT. And the fatigue crack growth resistance of CF/epoxy laminates at 77K was as high as that of epoxy No.113 at 77K near the threshold region. The difference of the fracture mechanism due to the test temperature and loading type (static or fatigue) was discussed on the basis of microscopic fracture mechanism consideration.