Investigation of sisal fiber cords impact to improve the mechanical properties of plaster-based composites

This study is relevant in the current context, where the world's attention is turned toward the exploitation of natural resources to replace fossil resources. It examines the potential of composite materials based on sisal cords. The cord shape's critical influence on adhesion is highlighted in this research to solve the problem of slippage between fibers and matrices. In addition, it explores also the challenges associated with fiber length, mass, and quality. The proposed chemical treatment with sodium hydroxide (NaOH) is studied to improve this interaction. First, it analyzes its effectiveness over different concentrations and time intervals. Subsequently, composites are developed with gypsum and sisal strands of specific dimensions, allowing for the assessment of their flexural strength based on the mass fraction of the strands, the length of the strands, and the percentage of water in the gypsum. The properties of the composite can be evaluated through mathematical modeling using the rule of mixtures (ROM), inverse rule of mixtures (IROM), and Hirsch models. According to the findings of this study, the chemical treatment has led to a significant improvement in the properties of sisal, in particular an increase in its tensile strength from 125 to 450 MPa. The biocomposite's flexural strength was increased by 40% by replacing single fibers with cords. The results suggest that alkali treatment and the use of cords instead of conventional fibers provide a significant improvement in composite strength. Thus, this study highlights the critical importance of cord form in the broader context of natural resource recovery.