Evaluation of repeated low energy impact damage in carbon-epoxy composite materials

The effect of repeated low energy impact on the performance of carbon-epoxy composites with three different stacking sequences was evaluated. The evolution of the macroscopic damage was characterized by a phenomenological equation, correlating the duration of the impact event, t, against the number of repeated impacts, Ni. The coefficients of the quadratic equation adjusted to the experimental points were related to the degree of freedom of the composite to deform (a1: the independent term), the rate of change of the composite properties due to the impact events (a2: the coefficient of the linear term), and the changing of the damage mechanism (a3: the coefficient of the quadratic term). These coefficients were shown to be dependent on the laminate stacking sequence, and by their analysis one can successfully describe the macroscopic behavior of the composites studied.