Prediction of effective three-dimensional elastic constants of translaminar reinforced composites

A Trans-Laminar;Reinforced (TLR) composite is defined as composite laminate with up to five percent volume of fibrous reinforcement oriented in a tran s-laminar fashion in the through-thickness direction. The objective of this work was to examine the effect of important parameters on elastic response . Detailed finite element models of unit cells were used to study the effec ts of adding TLR on the elastic constants. Parameters investigated included TLR material, TLR volume fraction, TLR diameter, TLR through-thickness ang le, ply stacking sequence, and the microstructural features of pure resin r egions and curved in-plane fibers. The work was limited to materials with a t least one ply interface. Adding a few percent TLR had a small negative ef fect on the in-plane extensional and shear moduli, E-x, E-y and G(xy), but a large positive effect (up to 60 percent) on the thickness direction exten sional modulus, E-z. The volume fraction and the axial modulus of the TLR w ere the controlling parameters affecting E-z. The out-of-plane shear moduli , G(xz) and G(yz), were significantly affected only with the use of a TLR w ith a shear modulus an order of magnitude greater than that of the composit e lamina. A simple stiffness averaging method for calculating the elastic c onstants was found to compare closely with the finite element results, with the greatest difference being found in the inter-laminar shear moduli, G(x z) and G(yz).