Abstract: A member of composite material incorporates at least one strain responsive member within a part at which a strain is induced by a load in use. A signal which is a function of a strain detetected by the strain responsive member is communicated to an indicator or monitoring device which registers the applied load causing the strain.In one embodiment a leaf spring for a vehicle comprises upper and lower elements of one or more superimposed strips of pre-impregnated longitudinally extending carbon fibres and an inner element of one or more strips of pre-impregnated glass fibres. During laying up of the strips two strain gauges (13, 14), which may be on or integral with a carrier strip, and their leads (13a, 13b, 14a, 14b) are introduced into the active length of the spring which experiences a bending moment on the application of a load. The gauges are positioned at a pre-determined distance apart which is maintained when the member is cured, as by hot press moulding.