Influence of curing pressure on the mode I static and fatigue delamination growth behavior of CFRP laminates

Curing conditions affect the mechanical properties of manufactured composite structures. However, the effect of curing pressure on the delamination behavior of laminates is still lack of investigation. This work studies the mode I static and fatigue delamination of carbon/epoxy laminates prepared at curing pressures of 1 MPa and 3 MPa. Delamination tests are conducted using double cantilever beam set-up. Test results show that more bridging fibers present in the laminates cured at 3 MPa, with more significant R-curve behavior, higher values of steady-state fracture toughness and maximum bridging stress than those in the laminates cured at 1 MPa. SEM images show that the laminates cured at 3 MPa mainly occur interlaminar damage while the major failure mechanism in the laminates cured at 1 MPa is the fiber/matrix debonding. A normalized model is proposed to describe the fatigue delamination behavior of laminates with fiber bridging effect. It shows that all fatigue data can be characterized by a single linear curve and curing pressure affects the slope of the linear curve. Furthermore, simulation for the delamination growth is conducted based on a tri-linear cohesive zone model. Good agreements between experimental and predicted load-displacement responses are achieved, illustrating the applicability of the established FE model.