On the 'ply discount method' for determining effective thermo-elastic constants of laminates containing transverse cracks

Elastic constants and thermal expansion coefficients of a laminate containing transverse ply cracks are often calculated by reducing selected elastic moduli of the damaged plies. This approach is often referred to as the 'ply discount method'. In the present paper, specific ply moduli required for reduction are identified by enforcing compatibility with inter-relationships that exist between the thermo-elastic properties of cracked and uncracked laminates. The effect of laminate geometry is investigated by comparing ply reduction factors as a function of crack density for a number of different stacking sequences. Reduction factors are obtained from higher order laminated plate models of composites containing transverse cracks. A simplified approach for determining inplane modulus reduction factors is also investigated.