DAMAGE EVOLUTION UNDER LONG-TERM, HIGH AND CONSTANT LOADING OF A CARBON/EPOXY LAMINATE

Overview & Synopsis

When a composite material of carbon fiber and epoxy resin is subjected to mechanical loading, different phenomena can lead to changes in its properties or even irreversible damage (propagation of cracks, debonding between folds, fiber breakage). The objective of this work is to study, under high loads and long periods, the propagation of transverse microcracks (diffuse damage) until the fracture of the laminate under matrix modes (instability). Since long term tests are necessary to characterize the damage evolution as well as the creep and stress relaxation phenomena, a testing machine was carried out. Optimal orientations ([45°,-45°]ns and [60°,-60°]ns) and specimen shape have been defined to study this phenomena. Experimental results are presented here and it is observed an evolution of the matrix damage under constant loads. This evolution is compared to the evolution of the matrix damage in the case of cyclic loads (fatigue) which in this latter case is faster.