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 stiffe ning of the host matrix due to micro-fiber reinforcement was observed. In the hybrid fiber composites, different fibers appear to act as add itive phases, i.e., they maintain their individual reinforcing capabil ities. The composites were also impact tested in uniaxial tension usin g a newly designed instrumented impact machine. When compared with sta tic test results, considerable sensitivity to stress-rate was noted; c omposites were found to be stronger and tougher under impact and the i mprovements were more pronounced at higher fiber volume fractions. The paper recognizes the potential of these composites for use in thin sh eet products and other similar applications, and stresses the need for continued research. In Part II of this paper, these composites will b e characterized under an applied flexural load and a fracture criterio n will be developed through crack growth tests.