Influence of the drilling quality on the fatigue compression behaviour of carbon epoxy laminates

In this work, we deal with the influence of the drilling quality of a composite material on its cyclic compression resistance. Two sets of drilling parameters were employed to produce two types of samples. One was drilled with no detectable damage; this set is considered as ‘defect-free’. For the second kind, we have intentionally introduced defects during the drilling phase. These two sets of specimens were subjected to the same compressive cyclic loading. The first set is considered to be a reference in order to evaluate the influence of the defects introduced by the drilling in the fatigue behavior of second set. The absolute secant modulus of specimens with important defects was slightly smaller than those of defect-free samples after 4×105 cycles. X-ray radiographies and microscopic observations were performed for determining the extent of damage through the thickness at different stages in interrupted fatigue tests. Finally, different criteria were used to correlate to the experimental damage.