Effect of fiber dispersion on multiple cracking of cement composites

High performance, fiber-reinforced composites are identified by their high strength and toughness associated with multiple cracking. If the composite is adequately reinforced, the bridging fibers will transfer the load and multiple cracking will occur when the subsequent transferred load cracks the matrix again. This study investigates the effect of dispersion of fibers on the multiple cracking behavior of fiber-reinforced composites. The electronic speckle pattern interferometry technique is used to record the location of crack initiation, the sequence of the multiple cracking, and the corresponding cracking stresses. Microstructural parameters at each crack location are statistically quantified by the theory of point processes. The size of the fiber-free areas and the fiber clumping are calculated at the crack cross sections. By using linear elastic fracture mechanics, the fracture toughness of the matrix is calculated. A strong relation between the cracking stress and the fiber-free areas in the composite is observed. It is shown that the toughness of the composite depends on the fiber clumping at the first crack cross section.