An experimental study to determine the dependence of the viscosity and shear stress of hydroxyl-terminated polybutadiene (HTPB) and dimeryl diisocyanate (DII) liner on curing time is presented. Viscosity and shear-stress were measured by HAAKE RheoStress 600 rheometer with parallel disks configuration at a constant temperature of 65 °C. The viscosity and shear-stress change were monitored for 8 h. Analysis of data showed that the liner viscosity and shear-stress dependency on time matched to pseudoplastic fluid model. For low shear-rates, the viscosity build-up is highest, with the logarithm of the viscosity being practically linear with time and the viscosity increases by more than two orders of magnitude for these cases. When the shear rates increase, the viscosity build-up slows down considerably with time and the viscosity is increased only by one order of magnitude.
A study of the influence of the reinforced fiber orientation and the propellant aluminum content on the ablation and erosion performance of Ethylene Propylene Diene Monomer type insulation is presented. A subscale solid rocket motor has been used, with ammonium perchlorate and hydroxyl-terminated polybutadiene propellant composition. Seven static firing tests were conducted: six with low Al and one with high Al content. The EPDM ar-ticles had four different Kevlar fiber orientations: circumferential, longitudinal, diagonal (45°), and random. Numerical simulations were supplemented to decipher the experimental outcome. The numerical results exhibit an over-prediction tendency, yet they show that the examination of post-fire charring of the insulation is insignificant. The test results indicate that the longitudinal fiber orientation has the least ablative resistance.
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