# Anisotropic Heat Transfer in Plane of Carbon Fabrics Reinforced Geopolymer Composite
## 1 Introduction  
Geopolymers are considered an insulating material due to their low thermal conductivity behavior [1], with additional fire proofing properties. Geopolymers emerge as the alternative eco-friendly material because of durability, flexural strength, and high temperature withstanding behavior [2, 3]. However, geopolymer is more brittle in nature, which hinders its application in various areas [4, 5]. This could result in failures in civil structure [6] in areas of the construction and building sectors. Geopolymer is chosen as an insulating material with low conductivity properties [7]. These properties of geopolymer allows for applications in the construction and building industries. The low thermal conductivity of an inorganic matrix phase of geopolymer could be enhanced or maintained by incorporating carbon fiber network materials as the supporting matrix [8]. However, brittleness of the geopolymer matrix could improve by incorporating carbon fibers in the geopolymer matrix. Carbon fabrics have low density, high stiffness, and high temperature tolerance, which could lead to applications in areas of the aerospace and civil engineering industries [9, 10]. Carbon fabric is composed of carbon crystals. A linear arrangement of these crystals forms a chain that results in a flat ribbon. A large number of these ribbons are braided together in different patterns to form carbon fabrics. Fibers are aligned in anisotropic material properties in carbon fabric. Continuous carbon fiber reinforced geopolymer matrix composites exhibit better mechanical properties [11]. Carbon fiber reinforced geopolymer composites have been widely used in various areas such as aerospace, construction, and building materials in structural applications [12, 13]. On the benefits side, materials with low conductivity could be used as insulation materials in energy-intensive industries with easy integration in the main assembled structure. In this scenario, geopolymer materials are attractive in various applications in fire protection coating materials [14, 15]. The geopolymer is prepared by mixing a silicate-based mineral, such as metakaolin, as a binder at room temperature (RT) [16]. The mixture undergoes curing at a temperature of 80 \({}^{\circ}\)C inside the vacuum furnace. Geopolymers have low thermal conductivity in the range of\(0.5<\) K \(<\) 1.0 W/m K [17]. Carbon fibers are known to have excellent thermal conductivities. However, if the interface between the matrix and fibers has poor thermal properties, it affects the overall thermal conductivity of the composite significantly. The goal of this article is to quantify the thermal conductivity of the matrix-fiber interface in a carbon fiber geopolymer composite. A geopolymer matrix can reduce the thermal conductivity by about a factor of ten. Therefore, to improve the conductivity of the composite, the improvement in the interface heat transfer coefficient should be accompanied by an improvement in the conductivity of the matrix as well as the distribution of fibers within the composite.  
To understand the heat conductivity of a carbon fiber in geopolymer composite, an approach has been discussed in this article with experiments and numerical simulations. The heat distribution within carbon fiber is predicted using an infinite domain wall approach, with a geopolymer as the matrix. The approach has been established on comparing the thermal conductivity of a carbon fiber reinforced geopolymer composite at various temperatures. The thermal conductivity value of the carbon fiber reinforced composite will allow for the categorization of the material in a low thermal conductivity material, which is a reduction in the category of insulating materials for structural applications.