Effects of Temperature and Strain Rate on the Dynamic Fracture Properties of HTPB Propellant

Abstract

[a] 1IntroductionHydroxyl-terminated polybutadiene (HTPB) propellant is widely used for the propulsion of missile and space launch vehicles. The solid propellant grain mays ubject to loads such as vibration, impact, among others, during shipping, ignition pressurization, and storage, which may cause damage as microcrack and cavity.Acrack propagating in ap ropellant grain creates extra surface area for burning which affectst he ballistic performance of the rocket motor. Especially under the ignitionp ressurization and the high acceleration conditions, the propellant may subject to dynamic loads.T he fracture initiation and propagationp roperties underh igh strain-rate are importanta spects for the structural integrity of solidr ocket motor.A no bvious error may occur if we use the properties under static state to evaluate the security of ag rain underd ynamic state. In service, the rocket motor is often requiredt oo perate over aw ide ranget emperature (in particularl ow temperature) which can cause significant changes in the physical and mechanical properties of the propellant. Therefore, it is necessary to study the temperature and strain-rate effects on the dynamic fracture properties in the propellant.Impact fracture properties of threen itrocellulose/nitroglycerine gun propellants have been measured in at hreepoint bend mode at moderate impact rates with an instrumented drop-weight impact tester [1].T he fracture toughness of plastic deformation zones underp lane stress conditions was approximately twice than that underp lane strain conditions. The impact fracture toughness of an itrocellulose/nitroglycerine gun propellant was foundt ob ev irtually independent of strain rate over the range from 3t o9 0s À1[2].A ne xperiment of fracture surface energy of as olid propellant under impact loads was conducted. The influence of strain rate on fracture toughnessh as beenp ointedo ut and as trong loading rate dependence has been observed [3,4].At present, research of the dynamic properties of HTPB/ AP propellant was focused on the high strain-rate constitutive models [5,6],a nd the dynamic fracture properties was also important for assessment of structure integrity of solid rocket motor. In the presentedw ork, the temperature and strain-rate dependence of the dynamic fracture toughness of HTPB propellant are studied, and the master curve or dynamic initiation fracture toughness was obtained using the temperature reduce strain rate. 2E xperimental Part Materials and Sample ConfigurationThe material investigated was manufactured by the casting methodc omprising of 86 %s olid particles (AP/AL), 10 % HTPB binder, and 4% others. All the particles ize obeys normald istribution,a nd the meanv alue of the big and small AP particles is about 215,1 50 mm, the variance is 19.5, 10.55 mm, respectively.T he mean valuea nd the variance of metallic aluminum particles is about 120 and 8 mm, respectively.Ac rackeds traight-through Brazilian disc Xi'an High-tech Institute Xi'an 710025, Shan'xi, P. R. China *e-mail:longbingfh@126.c...

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