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150 Mechanics and analysis of composite materials
(4.71)
where the stiffness coefficients are
(4.72)
where
El.2
E1.2 = , E12=E1~12+2G12, C=COS~, s=sin4 .
1 - VI2V21
Dependence of stiffnesscoefficientsA,, in Eqs. (4.72) on 4 was studied by S.W. Tsai
and N.J. Pagano (see, e.g., Tsai, 1987; Verchery, 1999). Changing powers of sin 4
and cos 4 in Eqs. (4.72) for multiple-angle trigonometric functions we can reduce
these equations to the following form (Verchery, 1999):
(4.73)
