Victor C. Li

Fracture Energy Optimization in Synthetic Fiber Reinforced Cementitious Composites

A study has been carried out on cementitious composites reinforced with various synthetic fibers, focusing on their tensile behavior, toughness, and fracture mechanisms. A model is formulated to predict the tensile behavior and fracture energy of fiber reinforced cementitious composites (FRC) with short, randomly distributed fibers. The model accounts for the pull-out of fibers oblique to the fracture surfaces (including snubbing friction effect), and the variation of the fiber/matrix interfacial shear stress during pull-out. Experimental and analytical results are shown to be in close agreement for the one class of fiber reinforcement which best satisfies the assumptions of the model. Systems which violate the assumptions exhibited different failure mechanisms and were observed to show less satisfactory reinforcement performance, especially the composite fracture energy. The model is used to examine the effect of fiber properties on composite post-cracking behavior and is useful in design of such material systems with optimum performance and cost effectiveness.

Effect of Material Structure on the Non-linear Fracture Parameters of Aggregative Concrete

ABSTRACT Comparisons of experimental data on the effect of material structure on the composite fracture properties of concrete with a recently developed theoretical model is presented. The meso-scale theoretical model of tension-softening behavior is based on the initiation and spreading of a dominant crack from the largest aggregate particle, subsequently intersecting other aggregates in its path, followed by complete material separation of the eventual crack plane by frictional pull-out of the aggregates. The limited but favorable comparisons between data and the theoretical predictions suggest the usefulness for further investigation into this preliminary model.