MICRO-FIBER REINFORCED CEMENT COMPOSITES .1. UNIAXIAL TENSILE RESPONSE

Stress-strain curves in uniaxial tension were obtained for micro-fiber reinforced cement composites reinforced with high volume fractions of carbon, steel, and polypropylene fibers both in the mono and hybrid (combination) forms. Considerable strengthening, toughening, and stiffening of the host matrix due to micro-fiber reinforcement was observed. In the hybrid fiber composites, different fibers appear to act as additive phases, i.e., they maintain their individual reinforcing capabilities. The composites were also impact tested in uniaxial tension using a newly designed instrumented impact machine. When compared with static test results, considerable sensitivity to stress-rate was noted; composites were found to be stronger and tougher under impact and the improvements were more pronounced at higher fiber volume fractions. The paper recognizes the potential of these composites for use in thin sheet products and other similar applications, and stresses the need for continued research. In Part II of this paper, these composites will be characterized under an applied flexural load and a fracture criterion will be developed through crack growth tests.