8/28/2023 0 Comments Carbon fiber strainThe exit cone is the region of the nozzle where gas flows from the propellant burning. Some of these items made of composites for launching vehicles are exposed during a certain period of time under extreme temperature excursions (above 1,000 ☌) and to high-speed gas flow (Mach 3), as is the case of the nozzle extension (exit cone), shown in Fig. The landmark of thermal protection systems used in rocketry are based on carbon fiber/phenolic resin composites due to their exceptional ablative properties, light weight and adequate strength after char formation ( Williams and Cury 1992 Nichols and Hall 1988a, b Hall 1988a, b). Besides, mass reduction for components such as fairing, fins and motor cases is critical since they represent an increase in payload ( Barbosa 2004 Martins 2014). Many components and integrated systems of launching vehicles are manufactured in composites in order to meet 2 basic design requirements for space vehicles that are stiffness and mechanical strength combined with low weight and heat resistance ( Savage 1993). In all the space vehicles used as space devices a thermal protection system is needed in order to protect the structure systems, as well as the electrical system and the payload ( Dias 2001). Additionally, microgravity experiments are conducted inside and outside the Earth’s atmosphere and missions to space exploration ( Gonçalves 2008). They represent the transport system by which satellites, human beings and inhabited stations are placed into Earth’s orbit. The launching and sounding vehicles are important devices for research and practical and commercial use of space. Also ablative systems based on organic polymer matrices are used as thermal protection structures ( Almeida 2007 Tick et al. These include mainly bulk carbon, ceramics, carbon/ceramic composites and ceramic matrix composites eventually coated with refractory materials such as HfC, ZrC, and SiC. The state-of-the-art thermal protection systems are based either on ablative or reusable material depending mainly on the mission and trajectory characteristics. KEYWORDS: Ablation, Carbon-phenolic, Shear strength. The lowest value for shear strength obtained experimentally was 4.05 MPa, which is greater than the ultimate value obtained analytically (2.35 MPa), fulfilling its structural function during the propulsion time. Significant morphological changes in the microstructure after heat treatments were observed. Also, morphological analysis was accomplished by optical microscopy and the observation of fractured surfaces, by scanning electron microscopy. Experimental data were compared with the results obtained theoretically. Specimens of the material (carbon fiber/phenolic resin composite) were subjected to heat treatment at 500, 1,000, 1,500 and 2,000☌, and measurements of shear strength and shear modulus were performed using the Iosipescu mode. This study investigates the shear properties evolution during the heat treatment of a carbon fiber/phenolic resin nozzle extension entrance (exit cone) which is part of an integrated nozzle of launching and sounding vehicles, developed at the Instituto de Aeronáutica e Espaço (SP), Brazil. Ablation is a complex multiscale problem where radiative and convective heating leads to the pyrolysis of phenolic resin matrix, resulting in the formation of a porous insulation char as thermal protection. Carbon fiber/phenolic resin composites have long been used as ablative materials in rocketry.
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