Modeling of the Mechanical Behavior of Fiber Reinforced Cement Based Composites Under Tensile Loads

The main objective of this research is to study and develop predictive models that covers various fundamental mechanisms influencing the stress‑strain response of fiber reinforced cement-based composites subjected to tensile loads. The analytical program is divided into two parts, one dealing with continuous fibers, the other with discontinuous fibers. In the first part, a non‑deterministic model is developed to predict‑the tensile mechanical response of cement based composites reinforced with long continuous fibers The model predicts composite stress and strain values at first cracking, during multiple cracking, at end of multiple cracking, and up to yielding or failure of the reinforcement. The model combines concepts of fracture mechanics, composite mechanics, and statistical strength distribution of the cementitious matrix. The second part of the analytical program deals with cement composites reinforced with short discontinuous fibers. Two problems are addressed, the composite elastic modulus, and the complete tensile stress‑strain response of the cementitious composite. Two fundamental models are derived to compute the composite elastic modulus. The first model is based on the concept of interfacial bond stress versus slip relationship, while the second model is a numerical scheme based on the homogenization theory. Then both concepts of bond‑slip and homogenization theory are deployed in a numerical scheme based on finite element analysis to predict the tensilestress‑strain response of the cement based fiber composite.

 

An extensive parametric analysis is carried out in this part of the program to study the effects of several parameters on the total response of the cement composite in tension. It is shown that pseudo‑strain hardening (or multiple cracking) is directly dependent on the fiber volume fraction, bond character, and fiber geometrical and mechanical properties. The effect of increased composite porosity due to fiber addition is also analyzed by the suggested model. Model prediction showed good agreement with experimental data obtained from previous tests undertaken at the University of Michigan and others available in the literature.