Abstract: A polymer composite material (10, 110, 210, 310) is described. The material includes a settable matrix material (12), a plurality of reinforcement members (14) and a plurality of capsule members (16). Each capsule member (16) includes a shell layer (22) encapsulating an indicator material (24). The polymer composite material comprises an initial condition in which each shell layer contains the indicator material, and a damaged condition in which at least one shell layer is ruptured, releasing indicator material. The polymer composite material is changed from the initial condition to the damaged condition by the application of a predetermined force to the polymer composite material.

Abstract: An acoustic transducer comprises an active element which changes in length along a first axis in response to an audiofrequency input signal, the element being mounted between an inertial mass and a foot which in use engages a surface whereby audiofrequency vibrations produced by the active element are transmitted to the surface, characterised in that the foot is hingedly connected to the inertial mass and the active element is located between the foot and the mass such that the angle between the first axis and the surface is less than 90°, in use.