Research On The Thermal Insulation Performance Of Quartz Fiber Reinforced Composite Materials

The thermal conductivity of quartz fiber reinforced composites with orthogonal tri-directional structure is discussed and characterized by the thermal conductivity of the materials in this paper.According to the unit cell model of orthogonal tri-directional structure,the mathematical models of thermal conductivity of warp,weft and Z yarn in three directions are established,which are verified by the experimental test of thermal conductivity.Firstly,unidirectional quartz fiber reinforced composites were designed and fabricated,and their transverse and axial thermal conductivity were tested,which laid a theoretical foundation for the establishment of the model.At the same time,the effects of different processing parameters(yarn fineness,warp density and weft density and fiber volume content)on the thermal conductivity of orthogonal tridirectional quartz fiber reinforced composites were studied.The results are as follows:(1)By comparing the experimental values of transverse and axial thermal conductivity of unidirectional quartz fiber reinforced composites with different fiber volume fractions and the theoretical values of Kingery,it is found that they are in good agreement.It is predicted that when the fiber volume fraction is 75%,the transverse thermal conductivity of unidirectional quartz fiber reinforced composites is 0.532 W·m-1.K-1,and the axial thermal conductivity is 1.097 W·m-1.K-1,which provides the basis for establishing the heat transfer model of orthogonal tridirectional quartz fiber reinforced composites.(2)Based on the basic theory of thermal conductivity-Fourier's law,the thermal resistance model of orthogonal tridirectional woven composites is established by means of the idea of circuit simulation in thermal resistance grid method.Combining the direction of fibers in orthogonal tridirectional preform and the heat transfer paths in warp,weft and Z directions,the thermal resistance model of orthogonal tridirectional woven composites is established according to the string.The resistance formula in series and parallel circuits determines the overall equivalent thermal resistance in all directions,and the corresponding calculation formula of the equivalent thermal conductivity coefficient is obtained.(3)By comparing the test values and model prediction values of the thermal conductivity of orthogonal three-dimensional quartz fiber reinforced composites,it is found that the predicted values of thermal conductivity in warp,weft and Z directions of composites are in good agreement with the test values,and the average errors of thermal conductivity in three directions are 5.59%,7.81%and 4.21%,respectively.The thermal conductivity of orthogonal tri-directional quartz fiber reinforced composites can be predicted by using this model.(4)Under different processing parameters,the volume fraction of fibers had the most significant effect on the thermal conductivity of composites.Under the condition that the yarn fineness and weft density remain unchanged,the volume fraction of fibers increases by 24.28%in warp direction,22.71%in weft direction and 17.03%in Z yarn direction when the volume fraction of fibers increases from 45%to 60%.(5)The thermal conductivity of composites is anisotropic in warp direction,weft direction and Z yarn directions when different processing parameters affect the thermal conductivity of composites.And the thermal conductivity in the three directions is related to the volume fraction of fibers in the corresponding directions.