STIFFNESS REDUCTION AND STRESS-ANALYSIS IN CRACKED [0M(0) 90N(0)]S LAMINATES/

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)degrees/90( n)degrees](s) laminates with transverse aligned cracks in the 90 degre es layer and to find the stress distribution between interacting crack s and in the vicinity of isolated cracks. The decaying curve describin g the loss of the effective Young's modulus in the tensile direction l ies slightly over the curve found by Hashin [7] with the help of simil ar stress assumptions. The reduction of Kirchhoff's modulus is predict ed in the same way as in Hashin [7] and Tsai and Daniel [28]. All comp onents of the state of stress are given by closed-form relations. The stresses within periodicity cells are expressed in terms of macrodefor mations. The explicit formulae for stresses derived in the present pap er make it possible to interrelate the crack spacing with a magnitude of the applied stress. To this end a local stress-type criterion of th e onset of cracks nucleation is used and reasonable good fit with expe rimental data of Highsmith and Reifsnider [9] is observed.