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Monitoring of bond-line stresses in case-bonded composite rocket propellants

: Mußbach, Günter; Bohn, Manfred A.

University of Pardubice, Institute of Energetic Materials:
18th Seminar on New Trends in Research of Energetic Materials 2015. Proceedings. Pt.1 : April 15-17. 2015, Pardubice, Czech Republic
Pardubice, 2015
ISBN: 978-80-7395-891-6
Seminar on New Trends in Research of Energetic Materials <18, 2015, Pardubice>
Fraunhofer ICT ()

In all case-bonded composite rocket propellant (CRP) types and in all case-bonded elastomer-bonded high explosive charges (HEC) so-named bondline stresses occur when the temperature is unequal to the curing temperature, means not equal to the so-named stress free temperature. The stresses or the forces, which act as tensile force on the bondline when temperature is decreased, can cause de-bonding from the case. Further on, the occurring tangential or ring stresses inside the material can lead to cracks inside the material, especially when the strain capability is not sufficient or decreases with ageing. Therefore a method is developed to monitor such stresses. The method enables a prediction-tool for critical loads with respect to failure of the material. Preferably such a method works non-destructively, means the quantities were determined without destruction or firing of the munitions, here rockets and high explosive warheads. In a first step, built-in stress sensors are used to follow the development of stress values during ageing and thermal cycling. The material is a typical composite rocket propellant with elastomeric HTPB-IPDI binder and AP and Al as solid fillers. The experimental set-up consisting of several small rocket motors equipped with stress sensors is explained. Results of the measurements are presented and discussed. Again to say any other elastomer binder with any other solid filler load are composite materials which suffer from these mechanisms outlined.