Determining of a closed-form relation for evolution of crack density and induced delamination in off-axis composite laminates under uniaxial loading condition

In this study a crack density based micromechanics methods in the framework of shear lag approach will be presented. This method is able to establish a dependent relationship for calculating the stiffness degradation and crack density evolution in each applied remote loading. Using this method by considering the effects of out of plane shear stresses, the stress-strain fields, displacement as well as the strain energies of different off-axis composite laminates with the stacking sequences of [±θ/90₄]_s will be calculated. Furthermore, the damage parameters of each damage modes including the matrix cracking and induced delamination will be applied. Using an appropriate fracture criterion, a closed-form analytical relationship will be derived for the mentioned composite laminates which predict the crack density evolution based on the axis applied stress. Finally, the results of extended shear lag model with different shear lag parameter will be compared with the available analytical and experimental results. Furthermore, a methodology will be represented which is able to predict the induced delamination evolution after occurrence of the matrix cracking in different off-axis laminates.