In the text a range of problems encountered by materials under extreme conditions has been described. To understand them, knowledge of the response of structure at the microscale is necessary and this has been assembled in the ambient state by materials science. Chemical reaction is possible in some substances in the condensed phase, and these are described as energetic, but in general physical deformation precedes chemistry in loaded materials. A fundamental focus for this field will be to try and understand the nature of the strength of solids. It will become clear that this is a difficult objective since complex behaviour results from the two classes of process that define strain: that in which length or volume changes with constant shape and one in which the shape changes at constant volume.

In what follows the response of these will be followed through from the microstructure at the atomic level to their form at the continuum. The various materials classes – metals, brittle materials, polymers and composites of all three – will be looked at to highlight particular features of their behaviour which go towards defining how the macroscopic boundary conditions of the loading excite response from the individual atomic architectures. The framework to describe observations is materials physics and this will be summarised below to aid the reader. It is by no means complete and much more rigorous texts exist for the student of materials science; however, it serves to allow a reader from an alternative background access to the necessary concepts to make the comments elsewhere in the text more tractable.