This study deals with the interlaminar fracture energy of a glass fiber reinforced polyester composite. Width tapered double cantilever beam (WTDCB) specimens are used for the test. The compliance and fracture behavior of the specimen as well as the effect of specimen geometry on fracture energy are studied. The fracture energy at liquid nitrogen temperature (77°K) is also studied. It is found that the fracture energy obtained decreases with increasing height of specimens, finally reaching a constant value. The minimum height requirement for the fracture test of Extren is one half inch. The fracture energy slightly decreases with a decrease in specimen taper. A load-deflection hysteresis is observed to increase with specimen width. Hysteresis is dependent on the beam volume, i.e., height, taper and crack length. The fracture energy at liquid nitrogen temperature (77°K) is about 3 times higher than that at room temperature and the fracture energy transverse to the fiber direction is slightly higher than in the fiber direction.
On the validity of the J-integral as a measure of the transverse intralaminar fracture energy of glass fiber-reinforced polyurethanes with nonlinear material behavior