Test parameters for evaluating toughness of glass-fiber reinforced concrete panels

The paper describes the ability of different test methods to measure the toughness of glass-fiber reinforced composites (GFRC). The three loading configurations used were: uniaxial tensile, third-point flexural, and instrumented impact. Fracture was observed to be dependent on the specimen geometry; gage length used; strain rate; and the extent of accelerated aging. Assuming that the local tensile stress-strain response can be expressed in the form of a bilinear ascending portion and an exponentially descending portion, both gage-length effects and loading geometry effects can be predicted. Using the analytical tensile stresss-strain responses, the experimentally observed flexural load-deflection and toughness were predicted. Possible methods to formulate aging mechanisms in the composites are also discussed. It is concluded that gage length, nonuniform strain distribution, geometry, and rate of loading must be carefully considered to characterize the toughness of GFRC.