Laminate construction

The composite constituents (fibre and resin) and volume fractions define a unidirectional composite ply or lamina. The unidirectional composite has exceptional mechanical properties in the direction of the reinforcing fibres but lesser mechanical properties perpendicular to the fibre direction. To achieve good multidirectional material properties for complex loading conditions, it is necessary to design a multidirectional lay-up of the basic unidirectional laminae. This lay-up is constructed by co-curing together individual unidirectional laminae. The multidirectional laminate can be tailored to match the expected loading conditions of the component by controlling the number of laminae that form the laminate, the angle of each lamina in the laminate and the stacking sequence of the laminae in the laminate. However, it should be noted that in any given direction of the multidirectional laminate, the properties are not equivalent to those of a unidirectional composite in its reinforced direction. Analysis methods can be used to predict the mechanical properties of the multidirectional laminate, however, once a design is finalised, test coupons must be created to assess the true properties and allowables for a successful candidate lay-up.