# Anisotropic Heat Transfer in Plane of Carbon Fabrics Reinforced Geopolymer Composite
## 3 Results and Discussion
### Experimental Measurement of Thermal Conductivity of the Composite
#### 3.2.2 Thermal Conductivity of the Carbon Fiber Reinforced Geopolymer Composite  
Insulation behavior of the geopolymer composites were assessed by measuring the thermal conductivity at a higher temperature. Figure 11a-c displays specific heat, thermal diffusivity, and thermal conductivity of the carbon fabric reinforced geopolymer composites as the function of annealed temperatures. A standard deviation of 1% was achieved from measuring five average samples. The increase in specific heat capacity in the carbon fiber reinforced geopolymer was observed as a function of annealed temperature (Figure 11a). There was a linear increase of specific heat from 950 to 1650 J/(kg K), which was observed over the annealed temperature. To the contrary, thermal diffusivity decreased over the range of an annealed temperature in the carbon fiber reinforced geopolymer composite. Figure 11b shows the thermal diffusivity decrease with an annealed temperature and remained constant at 250 \({}^{\circ}\)C for the carbon fiber reinforced geopolymer composite. Thermal conductivity of the carbon fiber geopolymer composite slightly changed from RT to an annealed temperature. However, the value of thermal conductivity of carbon fiber reinforced geopolymer composite lies in the range of 0.6-0.65 W/m K. The conductivity values fell within the range of insulating materials, such as brick (1.31 W/m K), soil/clay (1.1 W/m K), and concrete (0.4-0.7 W/m K) [11].  
There is not a significant difference in thermal diffusivity values in warp and weft directions because the fiber counts in the warp and weft directions are equivalent without any porosity in either direction. The effective thermal conduction of the carbon fiber reinforced geopolymer composite is based on the solid heat transfer and the radiative contribution. Results show that heat conduction was the principal contributor to the overall heat transfer, but its influence decreased when the temperature increased; this is due to the sum of different scattering processes. However, these scattering processes are predominantly dominant at different temperature ranges. Using a calorimetric method, we found that values on thermal diffusivity and thermal conductivity measured in-plane to the fiber axis decreased with respect to those obtained out-plane of laminate [24; 25].  
Figure 10: (**a**) Density of geopolymer (RT)and carbon fiber reinforced geopolymer composite (at room and at 1000 \({}^{\circ}\)C). (**b**) Thermal response of geopolymer and composite with the peak of the exothermic reaction.  
The simulation findings showed the value of heat distribution in the surface of the carbon fiber geopolymer composite (Figure 9b). The temperature distribution reached until 446 K at the center of the surface. However, the temperature distribution of the center plane and fiber structure remained at room temperature (Figure 9c). It showed the insulating behavior of the composite that matched well with the experimental findings from Figure 11c. The parameter that controls the composite thermal conductivity is the direction of fiber arrangement in the layout, where each fiber location varies along the direction of the fiber axis with adjoining location. The effect of the deviation of the fiber location from the ideal geometry has a very strong effect on the thermal conductivity of the composite.