Page 200 - Mechanics Analysis Composite Materials
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Chapter 4. Mechanics of a composite layer 185
I
Fig. 4.55. Two symmetric plies forming an angle-ply layer.
Fig. 4.56. Angle-ply layer of a filament wound shell. Courtesy of CRISM.
4.5.1. Linear elastic model
Consider two symmetric systems of unidirectional anisotropic plies (see Section
4.3) consisting of the same number of plies, made of one and the same material and
having alternating angles +4 and -4. Then, the total stresses a,, a,, and zxy acting
on the layer can be expressed in terms of corresponding stresses acting in the +4
and -4 plies as
(4.125)
where h is the total thickness of the layer. Stresses with superscripts ‘ + ’ and ‘-’ are
linked with strains E,, E,,, and y.Tl, which are assumed to be the same for all the plies
by Eqs. (4.71), Le.,
(4.126)
