جستجوی مقالات مرتبط با کلیدواژه « phenolic composite » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Hypothesis: Glass-reinforced composites are used in the production of passively cooled combustion chambers. To improve the performance of these composites as well as to decrease their costs, the use of micron sized silicon dioxide particles has been widely used. In this work, the possibility of producing glass phenolic composites with nanosized silica as an alternative to micron-scaled silicon dioxide was investigated. In order to disperse nanosilica in composites uniformly, a combination of sonication and high stirring was used. In all cases, the blends were prepared according to following procedure: the resin was weighed and diluted in methyl alcohol, and then the selected amount of nanosilica was added. The resultant mixture was sonicated and stirred for 1 h simultaneously. For preparation of glass fiber nanocopmpsites, a theoretical amount of chopped strands was weighed first and then the fibers were mixed with resin or the nanocomposites. Each produced paste was placed in a cylindrical shaped mold and then the mass was compression molded at a pressure of about 10 bar and cured at 180°C. The thermal resistance properties of the produced materials were studied using an oxy-acetylene torch. In depth temperature profiles taken through the thickness of the samples, ablation and loss of mass data of the post-test surfaces were used to evaluate the effects of nanosilica. Furthermore, to investigate the material post-test microstructure, a detailed morphological characterization was carried out using scanning electron microscopy. Findings: In comparison to neat glass/phenolic composite, the introduction of just 2, 4 and 6 wt% nanosilica particles embedded in the matrix improved the mass loss of nanocomposites about 12, 19 and 31%, respectively

Carbon/phenolic composites are used in the nozzle parts of solid rocket motors due to their heat-resisting، ablation، and high strength characteristics، which are required to endure the high temperature and pressure of combustion gas passing through the nozzle. One of the most important factors on erosion rate is the void content of the ablative composites. Facilities should be designed to simplify the exhaust of volatile components، in order to reduce the void content in the manufactured samples. Accordingly، to reduce the void percentage of carbon/phenolic composites in this study، samples were manufactured by the vacuum bag molding technique and cured in an autoclave. In order to compare the effect of manufacturing process on the ablation characteristics of carbon/phenolic composites، another batch of samples was produced by the acid curing method. The specimens were exposed to plasma torch flame based on ASTM E285-80. The results showed that the void percentage of samples which was manufactured by the autoclave process was 60% lower than the acid-cured samples، and this led to reduce the linear erosion rate of these composites.

Ablative materials play a strategic role in aerospace industry. These materialsproduce a thermal protection system which protects the structure، theaerodynamic surfaces and the payload of vehicles and probes duringhypersonic flight through a planetary atmosphere. In this work، we investigatedthe effect of refractory zirconium oxide on mechanical، heat stability and ablationproperties of asbestos/phenolic/zirconia composites. The asbestos/phenolic/zirconiacomposites were produced with different percentages of zirconia filler from 7 to 21%with average size of 7 μm and different number of layers of asbestos، say 3 to 6layers. These ablative composites were made by an autoclave curing cycle process. The densities of the composites were in the range of 1. 68 to 1. 88 g/cm3. Ablation properties of composites were determined by oxy-acetylene torch environment and burn-through time، erosion rates and back surface temperature in the first required 20 seconds. Thermal stability of the produced materials was estimated by means of thermal gravimetric analysis، in both air and nitrogen which consisted of dynamic scans at a heating rate of 10°C/min from 30 to 1000°C with bulk samples of about 20±1 mg. The results showed that when the amount of zirconia was raised from 7% to 21%، the erosion rate and the back surface temperature of composites increased by about 24% and 26% respectively، and the heat capacity of the composites increased byabout 85%. Also، the result showed that when the thickness of composites of 4. 2 mm was increased to 10. 1mm the burn-through time raised by about 226% and erosion rate dropped by about 41%. These composites displayed the maximum flexural strength when the amount of zirconia was about 14%.