Comparison Between Experimentally Determined and Theoretical Fiber Orientation Distribution in Strain Hardening Cementitious Composites (SHCC)

Strain hardening cementitious composites (SHCC) are a class of specially designed fiber-reinforced materials with good crack width control capacity and durability. The crack width of SHCC is mainly governed by the mechanical properties of fibers, interfacial properties between fibers and matrix, the fiber volume fraction as well as fiber orientation distribution. To quantify the effect of these parameters on SHCC behavior, micromechanical models have been developed. In previous studies, the fiber properties and parameters governing interfacial behavior have been experimentally obtained with well-established methods. However, the fiber orientation distributions were simply assumed to be 2D or 3D random (or the average between the two), but such assumptions have never been checked against test results. In this study, the experimentally examined fiber orientation distributions in SHCC tensile samples with PVA fibers were presented and compared with theoretical orientation analysis based on random distribution and consideration of the wall effect. The results show that the real fiber orientation forms a clear peak at around 20° while the pure wall effect analysis cannot reflect this phenomenon. A modified orientation analysis considering the simplified mortar flattening effect was then proposed. Large differences in simulated stress-crack width curves are found between the measured distribution and the wall-effect-induced distribution while the distribution obtained by the modified analytical model can greatly reduce the gap. The measured orientation distribution or proposed analytical approach can be used to replace random distributions in future work to reduce systematic simulation errors.