An Introduction to Composite Materials

In the previous chapter, procedures were described that allow prediction of the elastic response of a single lamina when loaded at an arbitrary angle to the fibre axis. It was shown that such uniaxial sheets tend to be highly anisotropic, with much greater stiffness when loaded parallel to the fibres than at significant angles to them. Moreover, other aspects of the elastic response are very different in different directions. For these reasons, it is common to stack laminae into bonded sets (laminates), making the elastic properties (and also the strength) more isotropic, and also opening up the possibility of tailoring the properties of a component to the loads that it will experience in service – potentially a major advantage of composites when compared with more conventional materials. In this chapter, the treatment of individual laminae is extended to the case of a laminate with an arbitrary stacking sequence, supplying an analytical tool of considerable value in the design of composite materials.