Estimate the strains-to-failure

Question

Solve the following problem:

Consider a quasi-isotropic laminate [0/90/ ± 45]S, 8 mm thick, made of carbon-epoxy AS4-3501-6. Use the truncated-maximum-strain failure criterion without matrix cutoff. Estimate the strains-to-failure using the data equation (1).

Equation (1):

E_1t = F1t/E₁   E_1c = F_1c/E₁

E_2t = F_2t/E₂   E2c = F₂c/E₂

γ_4u = F₄/G₂₃   γ_5u = F₅/G₁₃    γ_6u = F₆/G₁₂

Explain the mode of failure under the following loading conditions:

1. N_x = 1000 N/mm all other zero.

2. N_x = -1000 N/mm all other zero. Why is the strength ratio different from case(a) ?

3. N_xy = 1000 N/mm all other zero.

4. N_xy = -1000 N/mm all other zero. Why is this different from case(c) ?