Composite materials

A composite material responsive to mechanical and/or electrical stress comprises at least one substantially non-conductive binder and at least a first electrically conductive filler. The conductivity of the composite material in an unstressed state is related to the conductivity of the at least one substantially non-conductive binder and in a stressed state to the conductivity resulting from the presence of the at least first electrically conductive filler in the composition. The first electrically conductive filler is comprised of magnetite particles in a particle size distribution, and the at least one binder may include an oil, a gel, a wax a gel-wax, gel-ink or mixtures thereof.