Mechanical characterization of unidirectional CFRP thin strip and CFRP cables under quasi-static and dynamic tension

Under uniaxial tension, full stress-strain curves up to fracture and mechanical properties of a variety of CFRP cables having different structures are evaluated experimentally at three strain rates ranging from quasi-static (10-5 s-1) to dynamic (102 s-1). Such properties as tensile strength, chord or tangent modulus, strain at tensile strength and absorbed energy per unit volume are obtained. Experimental difficulties on stress and strain measurements and specimen fastening are overcome by introducing special instrumental arrangements and an expansive-cement fastening technique. For all cables, at quasi-static (10-5 s-1) and intermediate (10-2 s-1) strain rates, the stress-strain relation is linear. On the other hand, at a dynamic (102 s-1) strain rate, the stress-strain relation is non-linear and all cables tend to increase their elastic modulus and tensile strength. This obviously leads to increase of the absorbed energy per unit volume under dynamic tension. However, the strain at tensile strength remains almost the same at all strain rates. Thus, from a consideration based on the fracture strain criterion, it is concluded that strain rate insensitivity is assured for all cables.