The Analysis of Viscoelastic Stress of Thick Laminated Composite Cylinders at an Elevated Temperature

Effect of Transverse Matrix Cracks on the Relaxation Moduli of Linear Viscoelastic Laminates

“…The stress relaxation moduli of the transversely isotropic material used in the current work are obtained from [15]…”

“…The fiber direction compliance S 11 ¼ 5:9 Â 10 À8 =psi. In [15], Poisson's ratios v 12 ¼ 0:3 and v 23 ¼ 0:36 are assumed to be time independent. Some researchers have found that the Poisson ratios of viscoelastic materials are time dependent [16][17][18].…”

“…The subscripts ij of the relaxation function imply that each component of the relaxation moduli can relax in a different manner. However, the material properties obtained from [15] have time-independent Poisson's ratios. For this material, only two relaxation functions are required for a transversely isotropic material.…”

“…This implies that the reduction of the C 0, c ij and C 1, c ij in the viscoelastic constitutive equation must be the same as the reduction of the elastic moduli. The relaxation functions of a cracked ply are obtained using Equation (15). Note that after cracking, the lamina becomes an orthotropic material and the number of relaxation functions can be more than two.…”