Berner (1997) studied matrix damage of cross-ply laminate by combining a simplified

micro-mechanics model with finite element analysis and showed that the prediction of

damage is improved substantially with the incorporation of residual stresses. Aoki et al.

(2000) modeled and successfully predicted the leakage through the matrix cracks.

 The present objective is to investigate options available to minimize the increase in

thickness due to thermal residual strains for laminates designed subject to thermal and

mechanical loads. Deterministic designs were performed to investigate the following

effects: (i) temperature dependant material properties for strains analysis, (ii) laminates

designed to allow partial ply failure (matrix cracking), and (iii) auxiliary stiffening

solutions that reduce the axial mechanical load on the tank wall laminates.

 Composite Laminates Analysis under Thermal and Mechanical Loading

 Since the properties of composite materials, such as coefficients of thermal

expansion and elastic moduli, change substantially with temperature, classical lamination

theory (CLT) (e.g., Giirdal et al. 1999) is modified to take account of temperature

dependent material properties. The stress-free strain of a lamina is defined as

EF (Ia F = GAT, Where a is the coefficient of thermal expansion (CTE). When a is

a function of temperature T, the stress free strain is given by the expression


 aF = a(T)dT (4-1)


where Tero is the stress-free temperature of the material and Tserwce, is the service

temperature. From the equilibrium equation and vanishing of residual stress resultant, the

equilibrium of a symmetric laminate subjected to pure thermal load with uniform

temperature profile through the thickness can be expressed by