Page 264 - Mechanics Analysis Composite Materials

Chapter 5. Mechanics of laminates 249

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Fig. 5.14. Unbonded view of an antisymmetric angle-ply laminate.

where coefficients A,,,,, are specified by Eqs. (4.72). Taking again e = h/2 we arrive at
constitutive equations in Eqs. (5.50) in which

Comparing these coefficients with those entering Eqs. (5.50) and corresponding to a
quasi-homogeneous angle-ply laminate we can conclude that the antisymmetric
laminate has much more large coupling coefficients C14 and C24, and thus much
more pronounced extension-twisting coupling effect.

5.8. Sandwich structures

Sandwich structures are three-layered laminates consisting of thin facings and a
light-weight honeycomb or foam core as in Figs. 5.15 and 5.16. Because in-plane
stiffnesses of the facings are much higher than those of the core, while their
transverse shear compliance is much lower than the same parameter of the core, the
stiffness coefficients of sandwich structures are usually calculated assuming that
in-plane stiffnesses of the core are equal to zero. The transverse shear stiffnesses of

Fig. 5.15. Composite sandwich panel with honeycomb core.