Fatigue damage evolution in 3D textile composites

The broad range of applications of 3D textile reinforced composites requires an in-depth knowledge of their mechanical properties. Among those, the fatigue behaviour receives high demand in several industrial applications. In this chapter some experimental investigations are summarized to assess the influence of the three-dimensional architecture of the preform on the fatigue properties and fatigue damage evolution. The considered composite materials were produced using epoxy resins reinforced with: non-crimp 3D orthogonal weave E-glass fabric; 3D braided carbon fabric; structurally stitched carbon multi-ply preform. The tensile-tensile fatigue response in the principal directions, for several load levels, provides a complete understanding of the influence of the 3D reinforcements on the fatigue behaviour and on the damage initiation and development during cyclic loading. Moreover, post-fatigue residual quasi-static mechanical properties show the influence of the damage imparted.