Delamination properties of translaminar-reinforced composites

In the paper the delamination crack propagation is investigated in 3D woven carbon and glass fiber composites. Composites were produced in 3TEX company and had volume fraction of transverse fibers equal 2-5% of total volume of fibers. The reinforcement acts as crack bridging, greatly improving material resistance to delamination. In this paper investigation of this material has been performed using double cantilever beam technique and models elaborated for large scale bridging in UD composites. The following alterations and novelties are introduced: 1) The appropriate form and shape of specimens with glued additional metallic tabs was elaborated allowing to avoid the premature break of specimen arms; 2) Original loading device was designed to transfer high load directly to crack faces, and additional measurement of crack opening was proposed (as in the case of UD composite) to find the bridging law; 3) The convenient analytical formula for G _Ic calculation was proposed and used; 4) Instead of traditional R curve which is geometry dependent it was proposed to characterize the delamination resistance as function of crack opening displacement. The quantitative delamination characteristics for materials investigated are presented.