Phenomena in Composite Materials Caused by Gradient Heating

In earlier chapters we assumed that the temperature θ of a composite was uniformly distributed over the whole domain V occupied by the material (or by a specimen, a structure element). This assumption was necessary in order to establish a dependence of effective properties of composites on temperature θ(x, t) at a given material point x. The expressions for thermomechanical characteristics of composites derived above are applicable for the case of gradient heating, i.e. when temperature θ(x, t) changes in passing from one spatial point x to another within the domain V occupied by a composite structure at a fixed time t. Therefore all the aforementioned phenomena of changing (degradation) properties of composites under high temperatures will also take place under gradient heating. However under gradient heating there appear new specific phenomena in the behaviour of composites, which will be investigated below. As an example, the behaviour of composites is considered for textile materials, for which orthotropy axes are directed so that fabric layers are orthogonal to the Ox₁ axis.