The strengths in the expressions for F i , F i j may be interpreted, in the case of a lamina, as σ σ 1 c = transverse compressive strength, σ σ 1 t = transverse tensile strength, σ σ 3 c = longitudinal compressive strength, σ σ 3 t = longitudinal strength, τ τ 23 = longitudinal shear strength, τ τ 12 = transverse shear strength.