Page 374 - Mechanics Analysis Composite Materials

Chapter 7. Environmental. special loading, and manufacturing effects 359

where A = A~IA~z A:2.
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Thus, the panel under study experiences only in-plane deformation and twisting.
Displacements u and u can be determined with Eqs. (7.34), while the following
equations should be used to find w

The result is

The deformed shape of the panel is shown in Fig. 7.50.
Depending on the laminates structures and dimensions therc exist the whole class
of stable and unstable laminate configurations studied by Hyer (1 989).
Deformation and warping of laminates appearing after the manufacturing
process is over can occur not only due to cooling of the cured composite but also as
a result of material shrinkage due to release of fibers tension after the composite
part is removed from the mandrel or chemical setting of the polymeric matrix.
To demonstrate these effects, consider a thin unidirectional layer formed with
circumferential plies wound on a metal cylindrical mandrel (see Fig. 7.51) under
some tension. Because the stiffness of the mandrel is much higher than that of the
layer, we can assume that under cooling from the curing temperature Tc to room
temperature To the strains in the principal material coordinates of the layer are
governed by the mandrel with which the cured layer is bonded, i.e.

Fig. 7.50. Deformed shape of an angle-ply antisymmetric panel.

Fig. 7.51. A unidirectional circumferential layer on a cylindrical mandrel.