نوع مقاله : یادداشت فنی
1 دانشکده مهندسی مکانیک - دانشگاه خواجه نصیرالدین توسی
2 دانشکده مهندسی مکانیک - دانشگاه صنعتی خواجه نصیر الدین توسی
3 دانشکده مهندسی مکانیک - دانشگاه صنعتی خواجه نصیرالدین توسی
عنوان مقاله [English]
During atmospheric re-entry, a ballistic or space vehicle is subjected to severe aerodynamic heating and its successful return through the Earths atmosphere depends largely on the provision that is made for reducing aerodynamic heat transfer to its structure. For this purpose, an ablative heat shield is normally used, which undergoes physical, chemical, and mostly endothermal transformations. These transformations produce new liquid or gas phases, which are subsequently injected into the environment.The interfacial, thermal and ablation properties of carbon fiber/phenolic resin composites are evaluated in this study. Different materials, such as plain carbon fabrics, as reinforcement, resole type phenolic (IL800, Resitan Co.) as matrix, p-toluene sulfonic acid (PTSA) and polyvinyl Butyral resin (PVB) as additive, have been used in the synthesis of the composites. Four groups of samples were fabricated to be investigated by a plasma torch. In order to explore the interlaminar shear strength of the composites, short-beam shear tests were conducted.
Short-beam shear tests indicate that the interlaminar shear strength of the C/P/PVB composite is 17% greater than that of the other samples. Observations show that 20% PVB has an important effect on proper adhesion between carbon fibers and the resole matrix of C/P composites, and on achieving improved interlaminar characteristics.
The ablation test results reveal that composites with 20% polyvinyl butyral resin (C/P/PVB) have the highest ablation resistance, and the erosion rate (mm/s) of these specimens are 20% lower than other specimens. Additionally, the
high insulation index of the C/P/PVB samples indicates that these composites are the best ablative materials in the present study. But, results show that the mass reduction percentage of C/P/PTSA/PVB samples is around 28% lower than C/P/PVB samples. According to Table 3, addition of PVB to C/P composites caused
70% improvement in the thermal conductivity of C/P/PVB composites.
Regarding samples with 4-7 wt% PTSA, against our expectations, these samples, because of their porous structure, did not have appropriate ablative performance.