Delamination is one of the most critical failure modes in a laminated composite structure. In order to improve the interlaminar fracture toughness, the concept of “interlayer” has been applied to thermoset composite materials. In the present paper, the static and fatigue interlaminar fracture characteristics of a interlayer toughened carbon/epoxy, T800H/3900-2, were examined and compared with those of a thermoplastic composite, APC2, as a reference.
Fracture region transition, which is deflection of the crack path from interlayer to intralaminar, is observed in the static Mode I interlaminar crack growth of T800H/3900-2. Mode I interlaminar fracture toughness, GIR, decreases during the propagation in relation to the decrease of the interlayer fracture surface area.
The Mode II crack growth resistance curve (R-curve) was obtained under the constant CSD rate by applying the stabilized ENF test. The remarkable fracture region transition is not observed in the Mode II R-curve of T800H/3900-2, and the toughened carbon/epoxy composite exhibits excellent crack growth resistance under Mode II loading.
The Mode I fatigue crack growth rate of T800H/3900-2 was expressed as a function of the maximum energy release rate during cyclic loading. The fracture region transition is also observed. The transition in the fatigue test was completed after a shorter crack extension than that in the static test.