Bending effect of through-thickness reinforcement rods on mode II delamination toughness of ENF specimen: Elastic and rigid–perfectly plastic analyses

In this paper, a new simple metallic z-rod model is proposed to study the bending effect of the metallic z-rods on mode II delamination toughness of laminated composites. A new transverse shear force–deformation relationship for a metallic z-rod is obtained by using the classical beam theory and modeling its surrounding matrix as linearly elastic, rigid–perfectly plastic or linearly elastic–perfectly plastic springs. The bridging traction provided by a metallic z-rod to the mode II delamination toughness is assumed to be only the shear force carried by a z-rod created by the relative slippage between two substrate beams in an end-notched flexure (ENF) specimen, whereas the longitudinal sliding friction is assumed to make negligible contribution to the bridging traction. Mode II strain energy release rate (SERR) is employed to evaluate the influence of the metallic z-rods on the interlaminar fracture toughness of end-notched flexure (ENF) specimens. A parametric study of ENF specimens reinforced with the z-rods is conducted to demonstrate the effect of the new bridging mechanism by the metallic z-rods on the mode II delamination toughness.