Stiffness reduction and stress analysis in cracked [0m 0/90n 0]s laminates

Abstract

A new method of modelling effective properties and stress distribution in cracked laminates [12]–[17] is applied to assess the loss of the effective Young, Kirchhoff and Poisson moduli of the [0 m 0/90 n 0] s laminates with transverse aligned cracks in the 90° layer and to find the stress distribution between interacting cracks and in the vicinity of isolated cracks. The decaying curve describing the loss of the effective Young's modulus in the tensile direction lies slightly over the curve found by Hashin [7] with the help of similar stress assumptions. The reduction of Kirchhoff's modulus is predicted in the same way as in Hashin [7] and Tsai and Daniel [28]. All components of the state of stress are given by closed-form relations. The stresses within periodicity cells are expressed in terms of macrodeformations. The explicit formulae for stresses derived in the present paper make it possible to interrelate the crack spacing with a magnitude of the applied stress. To this end a local stress-type criterion of the onset of cracks nucleation is used and reasonable good fit with experimental data of Highsmith and Reifsnider [9] is observed.