This volume presents new models for the thermomechanical behaviour of composite materials taking into account internal physico-chemical transformations such as pyrolysis, thermodecomposition, sublimation and melting at high temperatures (up to 2000C). This is of great importance for the design of new thermostable materials for the investigation of reliability and fire safety of composite structures, the investigation of interaction of composites with laser irradiation, and for the design of heat-shield systems and so on. Structural methods are presented for calculating the effective mechanical and thermal properties of matrices, fibres, and unidirectional, disperse-particles reinforced and textile composites, in terms of the properties of their constituent phases. For the first time calculation methods are presented for characteristics such as the rate of thermomechanical erosion of composites under high-speed flow, and heat deformation of composites with account of chemical shrinkage. Great attention is paid to the comparison of modelling results with experimental data. Furthermore, the book has collected experimental results on mechanical and thermal properties of composites at temperatures up to 2000`C. The thermomechanical behaviour of composites taking internal heat and mass transfer into account is stated and solved. The book should be of interest to researchers and engineers designing composite structures, and for materials scientists developing advanced performance thermostable materials.