Dynamic Mechanical Response and Damage Mechanism of HTPB Propellant under Impact Loading.

Hengning Zhang,Yinggang Miao,Hai Chang,Han Wang,Meng Liu,Tao Chen,Xuezhong Fan

doi:10.3390/ma13133031

Abstract

The dynamic mechanical behaviors of Hydroxyl-terminated polybutadiene (HTPB) propellant was studied by a split Hopkinson pressure bar apparatus (SHPB) at strain rates ranging from 103 to 104 s−1. The obtained stress–strain curves indicated that the mechanical features, such as ultimate stress and strain energy, were strongly dependent on the strain rate. The real time deformation and fracture evolution of HTPB propellant were captured by a high-speed digital camera accompanied with an SHPB setup. Furthermore, microscopic observation for the post-test specimen was conducted to explore the different damage mechanisms under various conditions of impact loading. The dominated damage characteristics of HTPB propellant were changed from debonding and matrix tearing to multiple cracking modes of ammonium perchlorate (AP) particles, along with the increase of the strain rate. For the first time, the influence of AP particle density on the dynamic response of HTPB propellant was studied by analyzing the strain-rate sensitivity (SRS) index of HTPB propellant with two different filler content (80 wt.% and 85 wt.%), which deduced from a power function of ultimate stress and strain energy density. The result of this study is of significance for evaluating the structural integrity and security of HTPB propellant.

Highlights

As an important type of solid propellant, Hydroxyl-terminated polybutadiene (HTPB) propellant has been universally equipped in solid rocket motors (SRMs) for both military and civil use, because of its outstanding advantages, such as high energy level, good processability and excellent mechanical properties [1,2,3]
The solid propellant grain is usually exposed to different forms of impact loadings, such as accidental dropping, launch overload and fragment impact under attack, which correspond with strain rates spanning from 103 s−1 to 104 s−1 [12]
The investigated HTPB propellant specimen was fabricated by a typical slurry casting method, including with HTPB as polymer binder, ammonium perchlorate (AP) and aluminum particles as solid fillers, DOA as a including with HTPB as polymer binder, AP and aluminum particles as solid fillers, DOA as a plasticizer and other additives

Summary

Introduction

As an important type of solid propellant, Hydroxyl-terminated polybutadiene (HTPB) propellant has been universally equipped in solid rocket motors (SRMs) for both military and civil use, because of its outstanding advantages, such as high energy level, good processability and excellent mechanical properties [1,2,3]. The solid propellant grain is usually exposed to different forms of impact loadings, such as accidental dropping, launch overload and fragment impact under attack, which correspond with strain rates spanning from 103 s−1 to 104 s−1 [12]. These types of impact loading can cause severe failure and even lead to Materials 2020, 13, 3031; doi:10.3390/ma13133031 www.mdpi.com/journal/materials. It is of great importance to study the characteristics of the mechanical performance and failure mode of HTPB propellant under impact loadings. These studies can provide the supporting data for numerical simulations, which is beneficial to assess the safety and structural integrity of HTPB propellant

Methods

Results

Conclusion