Investigation of the Failure Mechanism of HTPB/AP/Al Propellant by In‐situ Uniaxial Tensile Experimentation in SEM

Abstract

The failure mechanism of a propellant consisting of hydroxyl terminated poly‐butadiene filled with ammonium perchlorate and aluminum (HTPB/AP/Al) was determined by performing in‐situ uniaxial tensile tests in a scanning electron microscope (SEM). The experimental test plan contained uniaxial tensile test experiments performed at room temperature (25 °C) at three different strain rates (30, 150 and 750 μm min−1). The in‐situ images and in‐situ videos collected by the SEM were correlated with the stress‐strain diagrams created with the tensile experiments, in order to relate the failure mechanism to the features found in the stress‐strain diagram. No significant strain rate dependency of the failure mechanism was observed when working with strain rates up to 750 μm min−1 and working at room temperature. The stress‐strain diagram showed indications of existing cracks and voids opening up prior to the creation of new cracks and/or voids in the sample, debonding of binder with AP particles as well as nucleation and coalescence of voids. On the fracture surfaces of the samples, it was apparent that the binder cleanly separated from the large AP particles but had a better bond with the aluminum particles. However, a difference in the appearance of a short drawing phase in the stress‐strain diagram of the propellant is observed at different strain rates. The presented results clearly demonstrate the major advantage of the combination of microscopic tensile tests with microscopic observations, linking the stress‐strain behavior to the mechanical deformation processes taking place in these propellant samples at the microscopic level.

Pendant Chains Are Not Just Decorations: Investigation of Structure‐Property Relationships of Azido Oxetane Polymers

“…They serve as the backbone of the energetic materials, bind the energetic solids and other ingredients in a plastic matrix, so that the material could maintain its shape and exhibits enough mechanical properties and safety for application. One of the widely used binders is hydroxyl-terminated polybutadiene (HTPB) in solid propellant [7][8][9], which provides the propellants with good performance in a wide temperature range. However, the non-energetic feature of HTPB limits further improvement of the energy of the rocket propellants and explosives.…”

Micromechanical Investigation of Debonding Processes in Composite Solid Propellants

“…To examine the micromechanical damage of solid propellant, the solid propellant was strained for SEM at room temperature. The equipment and procedures were similar toRamshorst [10]. Figure 1 shows a sequence of images with increasing stain concentration.…”

Evaluation of Mechanical Properties of Composite Solid Propellant by Genetic Engineering of Materials: Part A.

“…In 2016, Marthinus et al [2] studied the failure mechanism of an ammonium perchlorate/aluminum-/hydroxyl-terminated polybutadiene (AP/Al/HTPB) pro-pellant by in-situ scanning electron microscopy uniaxial tensile testing. Dur-ing tensile testing, cracks and voids opened up prior to three processes: the creation of new cracks and/or voids in the propellant sample, the debonding of the binder with AP particles, as well as the nucleation and coalescence of voids.…”