Research On Heat And Mass Transfer And Mechanical Properties Of Low Density Carbon/phenolic Composite

Reentry vehicle,e.g.spaceship return cabin,will undergo intense aerodynamic heat when entering the atmosphere.To protect the aircraft and internal equipments absorbing thermal energy,thermal protection system(TPS)is necessary.The ablation is widely used in the design of TPS.With the development of spacecraft,lightweight ablative materials are developed.Lightweight phenolic resin impregnation chopped carbon fiber materials,have low density and good thermal insulation performances.It is a new generation of ablation material of the TPS.The heat and mass transfer properties of the materials have great influence on the effect of thermal protection.Therefore,it is important to study and predict its properties,such as effective thermal conductivity,permeability and compressive mechanical properties.In this paper,we observe the microstructure of the material,and establish the microstructure analytical model of low density carbon / phenolic composites.The three-dimensional heat and mass transfer analysis is carried out by the Lattice Boltzmann method.The compressive mechanical properties are predicted by FEM and verified by experiments.Firstly,the micromorphology of low density carbon / phenolic composites is studied by SEM observation.Based on the microstructure characteristics,a random distributed fiber network is established.And the micro-model is pretreated as the numerical micro-model for the heat and mass transfer analysis.Secondly,the Lattice Boltzmann method(LBM)is used to analyze the heat and mass transfer of the numerical micro-scale model.Comparing the numerical results of LBM with the analytical results from two examples of heat transfer of silicon film and top drive flow,the process of two dimensional heat and mass transfer analysis using LBM is verified.Then,three dimensional LBM model are carried out.The effective thermal conductivity and permeability of the low density carbon / phenolic composites are obtained.The results are in good agreement with the experimental results.The effects of temperature,porosity,fiber orientation and fiber volume fraction on the effective thermal conductivity and permeability are also investigated.Finally,the compressive mechanical properties of low density carbon / phenolic composites are studied by experiments and numerical methods.Some samples of low density carbon / phenolic composites are carbonized.Then compressive tests of carbonized and non-carbonized samples are conducted.The compressive modulus and compressive strength are obtained.Compared with the non-carbonized samples,the compressive strength of carbonized samples decreases by 50.27%,and the compressive modulus decreases by 28.44%.According to the fracture morphologies,the materials exhibit two main failure modes: elastic bending and buckling.The compressive strength and modulus are predicted by ABAQUS,and compared with the experimental results.