Experimental Insight Into the Modulation of Mechanical and Thermal Properties of Fibre-Reinforced Geopolymer Composites

The aviation industry has increasingly relied on advanced composite materials to meet demands for improved mechanical properties and specialized features. Geopolymer composites, reinforced with natural fibres such as jute and sisal, present a sustainable and cost-effective alternative to conventional structural materials. Despite their potential, a comprehensive understanding of their mechanical and thermal properties, particularly when derived from a combination of liquid and solid precursors, remains underexplored. This study investigated fiber-reinforced geopolymer composites using a novel matrix comprising sodium silicate (liquid) and sodium aluminate (powder), combined with metakaolin, an alkaline activator, and glass powder. Sisal and jute fibers were incorporated via hand lay-up, and samples were cured at 90°C. Mechanical properties were evaluated through tensile and compressive tests (ASTM C1275, ASTM D695), while thermal stability was assessed via thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and derivative thermogravimetry (DTG).The sisal-reinforced composite exhibited superior tensile strength (48.44 N/mm²) and Young’s modulus (166.66 MPa) compared to jute (12.35 N/mm², 66.66 MPa). Compressive strength reached 14.98 N/mm² for the base matrix. TGA revealed weight losses of 18.82% (jute) and 21.84% (sisal) at 910°C, with sisal showing higher thermal degradation but jute demonstrating better residual mass retention (81.70% vs. 77.27%). DSC identified melting points at 124.4°C (jute) and 122.2°C (sisal), with latent heats of fusion of 476.50 J/g and 611.70 J/g, respectively. The study highlights the viability of sisal composites for structural applications due to their mechanical strength, while jute composites offer enhanced fire resistance. The use of a hybrid liquid-powder precursor system advances geopolymer synthesis methods. These findings underscore the potential of natural fiber-reinforced geopolymers in sustainable engineering, with implications for fire safety, structural design, and material optimization in high-temperature environments.