Comparative Analysis of Thermal and Mechanical Behaviour of Natural and Synthetic Fiber-Reinforced Geopolymer Composites for Sustainable Aerospace Applications

Environmental concerns over cement-based composites have prompted the development of geopolymer alternatives. Reinforcement with fibers—both natural and synthetic—enhances their mechanical and thermal performance, enabling their potential use in aerospace and structural applications. Geopolymer composites were prepared using metakaolin and aluminum silicate activated by sodium hydroxide and sodium silicate. Four fiber types—natural (hemp, sisal) and synthetic (basalt, E-glass)—were incorporated. Standard tests (ASTM) were conducted to evaluate tensile, compressive, and flexural strength. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), and X-ray fluorescence (XRF) were used to assess thermal stability and phase composition. Hemp-reinforced composites showed the highest tensile strength among natural fibers (12.4 MPa), while basalt exhibited superior compressive strength (42.5 MPa). E-glass fibers yielded the highest flexural strength (25.4 MPa). TGA indicated thermal degradation for natural fibers around 350°C, while basalt and E-glass remained stable up to 500°C. XRD confirmed crystalline geopolymer formation, and XRF revealed high silica and alumina content. Both fiber type and orientation significantly influence geopolymer composite behavior. While synthetic fibers offer higher mechanical performance, natural fibers provide adequate strength and thermal resistance with added environmental benefits. This dual advantage positions fiber-reinforced geopolymers as sustainable alternatives for high-performance applications.