Analytical modeling of strength in randomly oriented PP and PPTA short fiber reinforced gypsum composites

Fiber reinforced gypsum are prevalent building materials in which short fibers with high tensile strength are embedded into a gypsum matrix to produce supplemental strong and lightweight construction materials. Due to confrontation to a rising risk of death and economic disaster in earthquake-prone areas, quake-resistant materials and structures should be employed for building constructions. Gypsum based composites as a unique candidate for this purpose reduce the risks and produce much confident construction materials for residential buildings. In this work tensile strength of gypsum composites with different volume fraction of polypropylene (PP) and poly-paraphenylene terephthalamide (PPTA) fibers up to 15% were studied. Stress transfer ability from matrix to fibers were analyzed using theoretical shear lag analyses, scanning electron microscope, and pull out tests. The interfacial characteristics were also studied by scanning electron microscope (SEM). The ability of the composites to withstand against longitudinal tensile load was also studied by tensile tests of dog-bone shaped, random oriented fiber reinforced gypsum. Tensile strength of randomly oriented short fiber reinforced gypsum was evaluated by a mathematical model. The obtained results from the model and experimental results have been compared and discussed.