Session: Virtual Presentations in Acoustics, Vibration, and Phononics

Paper Number: 96468

96468 - Phase-Field Modelling for Crack Evolution of PBX Under Thermomechanical Loadings 

Polymer-bonded explosive (PBX), also known as plastic-bonded explosive, is a typical kind of explosive powder with synthetic polymer bonded together explosive composite materials. It has excellent explosion performance and thus is widely applied in the military and civilian industries. The PBX mechanical properties exhibit high sensitivities to the action of various types of loads, which is closely related to microscopic damage mechanisms within the material. The applied loads vary considerably, with amplitudes ranging from a few MPa to as high as several tens of GPa and durations lasting from the order of μs to ms. The cracking evolution is essential to the PBX applications in a strict control manner. However, PBXs are dangerous energy-bearing materials, and the mechanical experiments to measure their mechanical properties are costly and also challenging. Therefore, theoretical analysis and numerical simulation are anticipated to explore the sensitivities of PBX mechanical properties and also the influence of crack evolution.

In this paper, the fracture phase-field method is proposed to numerally simulate the process of work done by PBX explosive gas, which reveals the typical microscopical mechanism of crack evolution and establishes a computational model for crack propagation under the coupled thermomechanical effects. The proposed model introduces a phase-field fracture variable to characterize the smooth transition between the structural body and the crack. Through the fracture phase-field modeling, cracks initiate and propagate spontaneously in a given mesh with the evolution of the phase-field fracture variable, and their mechanical properties are passed to the local damage areas. Since the phase-field model can obtain the geometric location of the cracks by evaluating the phase-field fracture variables, the proposed model is free from tracing the complicated crack propagation paths. This is an appealing advantage over various discrete methods based on crack path tracing. In addition, PBX has a multi-phase inhomogeneous microstructure with the energy-containing HMX filler particles randomly distributed in the polymer binder. As commonly assumed in practice, the HMX is considered to be a linear isotropic elastic material. Therefore, the PBX microstructure in this study consists of elastic HMX particles (approximately 95% in mass) and the typical viscoelastic binder material Estane 5703. The constitutive behavior of this viscoelastic binder material is described by a user-defined material model (UMAT) in Abaqus. Moreover, it is preferred to create a PBX model that is compatible with the real microstructure, and thus a Voronoi tessellation is adopted. Correspondingly, the HMX particles are represented by polygons in the Voronoi tessellation, and the polygons are bonded by the adhesive Estane 5703. First, the Voronoi tessellation is generated in Python, and the coordinates of the crystal vertices are extracted. Then, these coordinates are imported into Abaqus through a script to generate the corresponding parts, which provide input conditions for the analysis step. Therefore, with the material properties defined by UMAT, quantitative relationships between crack evolution and the applied thermo-mechanical loadings are achieved by the proposed fracture phase-field method. This provides the numerical basis for understanding and controlling the initiation mechanism of PBX explosion.

Presenting Author: Jiaqi Zhu Northwestern Polytechnical University

Presenting Author Biography: Xu Long is currently an Associate Professor at Northwestern Polytechnical University, China. He received his B.S. from the Department of Engineering Mechanics, Tongji University, China in 2006, M.S. from the Institute of Mechanics, Chinese Academy of Sciences, China in 2009 and Ph.D. from the Department of Structure and Mechanics, Nanyang Technological University, Singapore in 2013. Later, he worked as a Researcher Fellow at Nanyang University of Technology. In 2014, he worked as a Senior Finite Element Analyst at INTECSEA, a world-renowned engineering consulting company, of WorleyParsons Group. He was invited to be the Associate Editor of Computer Modeling in Engineering &amp; Sciences. He was also invited to be the Guest Editor-in-Chief of Journal Frontiers in Materials (JCR Q3, IF=3.515) and Coatings (JCR Q3, IF=2.881).<br/>His research interests are related to the mechanics of electronic packaging. In recent years, he has published more than 70 papers in mainstream mechanics and materials journals, including more than 40 SCI-indexed articles as first author and corresponding author (among which, 14 are indexed in CAS Q1 and Q2 journals). As the first or only author, he has published 2 books by Science Press, China. His paper was selected as the Featured article in Journal of Micromechanics and Molecular Physics (JMMP). According to Google Scholar, the citations of his publications are 908 with the h-index of 19 and i10-index of 32. Prof. Long won the first prize of Science and Technology Award of Shaanxi Colleges and Universities in 2017 and 2019, Outstanding Paper Award of ICEPT in 2018, Emerald highly Commanded Award in 2020, Outstanding Paper Award of Dassault Syst&#232;mes China Simulation User Conference in 2021, and First Prize of Outstanding Paper of the Joint Academic Conference of Micro Assembly Process Technology Center of CASC. He has established long-term cooperation with China Aerospace Science &amp; Technology Corp (CASC), China Aerospace Science &amp; Industry Corp (CSIC), China Academy of Engineering Physics and Huawei Corp., etc.

Authors:

Xu Long Northwestern Polytechnical University
Jiaqi Zhu Northwestern Polytechnical University
Yutai Su Northwestern Polytechnical University
Kim S. Siow Universiti Kebangsaan Malaysia
Chuantong Chen Osaka University