Pyrolysis Behavior, Pyrolysis Kinetics, Heat Transfer and Pyrolysis Simulation of Almandine/Boron Phenolic Resin Ceramizable Composites

Ceramizable composites have attracted great interest for the thermal protection of hypersonic vehicles. In our research described here the pyrolysis process of almandine/boron phenolic resin ceramizable composites was investigated; we note it can be divided into three stages (room temperature to 300 degrees C, 300 degrees C to 700 degrees C and 700 degrees C to 1300 degrees C). In addition, the pyrolysis products were identified by an analytical pyrolyzer coupled with a gas chromatography/mass spectrometry set-up (Py-GC/MS), and they were composed of phenols (69.82%), aromatic hydrocarbons (23.89%), and aromatic ethers and aliphatic esters (6.29%). Furthermore, the possible pyrolysis routes were proposed. Moreover, the pyrolysis kinetic parameters were calculated, and the activation energy, order of the reaction and pre-exponential factor were 54.18 KJ/mol, 0.869 and 2.828 s-1, respectively. In addition, Comsol Multiphysics finite element software was used to simulate the heat transfer and pyrolysis behavior. After the composite (with a thickness of 10 mm) was heated for 200 s at a heat flux of 480 KW/m2, the surface and back surface temperatures were 1200.6 degrees C and 163.7 degrees C, respectively. The thicknesses of the carbonized, pyrolysis and original layers were 2.11, 3.67 and 4.22 mm, respectively, which reflects the good thermal insulation behavior of the composite. We suggest the combination of calculation and simulation results can provide a theoretical basis for the design of thermal protection systems for hypersonic vehicles which are able to meet long-term and large-area thermal protection requirements.