ABSTRACT

The basic mechanical tests used to characterize a lamina (i.e., tension, compression, and shear) must be performed to experimentally characterize a laminate as well. Sometimes, a flexural test is also performed on a laminate beam specimen. However, the complexity of the mechanical behavior of a laminated plate (Figure 15.1) is considerably greater than that of the lamina discussed in previous chapters. Because the laminate generally includes off-axis plies (a unidirectional composite consisting of multiple unidirectional laminae is sometimes also referred to as a laminate), the stress state in a given ply is biaxial. Moreover, at free edges, a fully three-dimensional stress state develops (Pagano and Pipes 1971, 1973, Pipes et al. 1973), and edge delamination may occur. As shown in the works cited previously, however, the free-edge interlaminar stresses decay to small magnitudes within a boundary-layer region, which extends only about one laminate thickness in from the free edge. Classical laminated plate theory, reviewed in Chapter 2, is an accurate predictor of the stress state in the remainder of the laminate and of the overall structural behavior of the laminate. In this chapter, all analysis is therefore based on classical laminated plate theory.