scholarly journals Computational Investigation of Crack-Induced Hot-Spot Generation in Energetic Composites

2021 ◽  
Vol 5 (8) ◽  
pp. 210
Author(s):  
Xingzi Yang ◽  
Liqiang Lin ◽  
Justin Wilkerson ◽  
Xiaowei Zeng
Keyword(s):  
Computational Model ◽  
Cohesive Zone Model ◽  
Volume Fraction ◽  
Hot Spot ◽  
Local Heat ◽  
Zone Model ◽  
Binder Phase ◽  
Polymer Bonded Explosives ◽  
Lower Temperature ◽  
Energetic Composites

The sensitivity of polymer-bonded explosives (PBXs) can be tuned through adjusting binder material and its volume fraction, crystal composition and morphology. To obtain a better understanding of the correlation between grain-level failure and hot-spot generation in this kind of energetic composites as they undergo mechanical and thermal processes subsequent to impact, a recently developed interfacial cohesive zone model (ICZM) was used to study the dynamic response of polymer-bonded explosives. The ICZM can capture the contributions of deformation and fracture of the binder phase as well as interfacial debonding and subsequent friction on hot-spot generation. In this study, a two-dimensional (2D) finite element (FE) computational model of energetic composite was developed. The proposed computational model has been applied to simulate hot-spot generation in polymer-bonded explosives with different grain volume fraction under dynamic loading. Our simulation showed that the increase of binder phase material volume fraction will decrease the local heat generation, resulting in a lower temperature in the specimen.

scholarly journals Combined Numerical-Statistical Analyses of Damage and Failure of 2D and 3D Mesoscale Heterogeneous Concrete

2015 ◽  
Vol 2015 ◽  
pp. 1-12
Author(s):  
Xiaofeng Wang ◽  
Andrey P. Jivkov
Keyword(s):  
Cohesive Zone Model ◽  
Volume Fraction ◽  
Simulation Method ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Zone Model ◽  
Generation Process ◽  
Cohesive Elements ◽  
Damage And Failure ◽  
2D And 3D

Generation and packing algorithms are developed to create models of mesoscale heterogeneous concrete with randomly distributed elliptical/polygonal aggregates and circular/elliptical voids in two dimensions (2D) or ellipsoidal/polyhedral aggregates and spherical/ellipsoidal voids in three dimensions (3D). The generation process is based on the Monte Carlo simulation method wherein the aggregates and voids are generated from prescribed distributions of their size, shape, and volume fraction. A combined numerical-statistical method is proposed to investigate damage and failure of mesoscale heterogeneous concrete: the geometrical models are first generated and meshed automatically, simulated by using cohesive zone model, and then results are statistically analysed. Zero-thickness cohesive elements with different traction-separation laws within the mortar, within the aggregates, and at the interfaces between these phases are preinserted inside solid element meshes to represent potential cracks. The proposed methodology provides an effective and efficient tool for damage and failure analysis of mesoscale heterogeneous concrete, and a comprehensive study was conducted for both 2D and 3D concrete in this paper.

The Research of the Effective Moduli of Particle Reinforced Polymer Composites Based on Interface Debonding

2009 ◽  
Vol 413-414 ◽  
pp. 211-217
Author(s):  
Xin Long Chang ◽  
Bin Jian ◽  
Chang Ouyang
Keyword(s):  
Polymer Composites ◽  
Cohesive Zone Model ◽  
Volume Fraction ◽  
Micromechanical Model ◽  
Interface Debonding ◽  
Zone Model ◽  
Effective Moduli ◽  
Reinforced Polymer ◽  
The Matrix ◽  
Particulate Size

This paper is devoted to studying influences of matrix/particle interface debonding and particulate size in micromechanical predictions of the effective moduli of particulate reinforced polymer composites (PRPC). The PRPC is regarded as a three-phase composite that includes the matrix, particle and interphase. The formulation for the effective moduli of the interphase is derived by the cohesive zone model, and combined with the Mori-Tanaka method, the micromechanical model for the effective moduli of the PRPC is formulated with emphasis on the effects of the matrix/particle interface, particulate size and volume fraction. The numerical example shows that the interface debonding, the particulate size and volume fraction have significant influences on the effective moduli of PRPC. The effective moduli of the PRPC can be used to characterize its damage degree.

Numerical Analysis of Mesostructure Damage for Composite Solid Propellant Using a Combined XFEM-Cohesive Zone Model

2014 ◽  
Vol 551 ◽  
pp. 71-76
Author(s):  
Jiu Ling Zhao ◽  
Bo Gao ◽  
Jiu Fen Zhao
Keyword(s):  
Numerical Analysis ◽  
Solid Propellant ◽  
Cohesive Zone Model ◽  
Volume Fraction ◽  
Particulate Composite ◽  
High Volume ◽  
Zone Model ◽  
Composite Solid Propellant ◽  
Wide Size Distribution ◽  
Composite Solid

Composite solid propellant is a particulate composite with high volume fraction and wide size distribution, macroscopic mechanical behavior of SP is strongly depended on its mesostructure. This work presents a numerical analysis of mesostructure damage for SP based on XFEM and CZM method. A simplified physical model is used for the validation of the proposed method. It is shown that the result of crack extension agrees with experiment of Micro CT scan on the whole. Numerical simulations also indicate the fact that initiation of SP damage takes place at the interface of particle and matrix. At last, the relations of macroscopic strain and stress of SP with 55% volume fraction and 65% volume fraction AP are predicted based on mesostructure simulation and compared with experiments.

scholarly journals Postbuckling behavior of functionally graded CNT-reinforced nanocomposite plate with interphase effect

2019 ◽  
Vol 8 (1) ◽  
pp. 496-512 ◽  
Author(s):  
Ashish Kumar Srivastava ◽  
Dinesh Kumar
Keyword(s):  
Elastic Properties ◽  
Cohesive Zone Model ◽  
Volume Fraction ◽  
Matrix Material ◽  
Shear Deformation Theory ◽  
Functionally Graded ◽  
Zone Model ◽  
Postbuckling Behavior ◽  
Compressive Loads ◽  
The Matrix

Abstract The present paper is aimed to study the buckling and postbuckling response of functionally graded carbon nanotube (FG-CNT)- magnesium (Mg) nanocomposite plate with interphase effect. Interphase zone is characterized by employing a cohesive zone model for its elastic modulus and thickness. An equivalent solid fiber (ESF) of CNT and interphase is modeled and dispersed into the matrix material by utilizing random sequential adsorption (RSA) technique. The effective elastic properties of the nanocomposite are computed by finite element method (FEM) based numerical homogenization technique. The obtained elastic properties of nanocomposite are utilized to investigate the buckling and post-buckling behaviour of different functionally graded (i.e., FG) nanocomposite plates modeled by varying the volume fraction of CNT/ESF along thickness direction, under in-plane compressive loads. The non-linear formulation is based on first-order shear deformation theory and von Karman’s assumptions. It is found that considering the interphase between CNT and Mg matrix would result in decrease in buckling load and postbuckling strength of FG-CNT-reinforced nanocomposite plate as compared to nanocomposite without interphase. It is also reported that the higher volume fraction of CNTs near top and bottom surfaces than the middle portion of nanocomposite plate provide better resistance to buckling and postbuckling.

Numerical analysis of cracked aluminum plate repaired with multi-scale reinforcement composite patches

2020 ◽  
Vol 54 (28) ◽  
pp. 4341-4357
Author(s):  
A Yousefi ◽  
M Mosavi Mashhadi ◽  
M Safarabadi
Keyword(s):  
Mechanical Properties ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Cohesive Zone Model ◽  
Volume Fraction ◽  
Aluminum Plate ◽  
Zone Model ◽  
Composite Patch ◽  
Different Thickness

In this study, numerical modeling is used to investigate the performance of a single-sided composite patch with different scale fillers, as reinforcement of a cracked aluminum plate under static tension. The main concerns of previous studies are about the geometry of patches, composite layups, and failure of adhesive. In this research, the effect of patch properties such as size and fiber volume fraction, the thickness of patch, and thickness of adhesive on the overall performance of the cracked aluminum plate are investigated numerically. Indeed, first, a 3 D representative volume element (RVE) is adopted to calculate the mechanical properties of carbon nanotube (CNT)/epoxy and carbon fiber (CF)/epoxy composite patch at each specified volume fraction for investigating the effect of patch properties on the performance of a single-sided patch for crack repairing. In this regard, the cohesive zone model is adopted to analyze the debonding between the epoxy matrix and reinforcement to characterize the mechanical properties of composite patches. Finally, a linear 3 D finite element analysis is performed to calculate the stress intensity factor (SIF) for cracked aluminum plate repaired by a single-sided composite patch at each specified reinforcement volume fraction for different thickness of patch and different thickness of adhesive. The results demonstrated that the stress intensity factor highly depends on the patch properties (patch stiffness) in addition to patch thickness and adhesive thickness.

scholarly journals Ultrasonic Deicing Efficiency Prediction and Validation for a Flat Deicing System

2020 ◽  
Vol 10 (19) ◽  
pp. 6640
Author(s):  
Zhonghua Shi ◽  
Zhenhang Kang ◽  
Qiang Xie ◽  
Yuan Tian ◽  
Yueqing Zhao ◽  
...  
Keyword(s):  
Lead Zirconate Titanate ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Lead Zirconate ◽  
Efficiency Factor ◽  
Zone Model ◽  
Shear Stresses ◽  
Stress Distributions ◽  
Total Energy Density ◽  
Average Shear

An effective deicing system is needed to be designed to conveniently remove ice from the surfaces of structures. In this paper, an ultrasonic deicing system for different configurations was estimated and verified based on finite element simulations. The research focused on deicing efficiency factor (DEF) discussions, prediction, and validations. Firstly, seven different configurations of Lead zirconate titanate (PZT) disk actuators with the same volume but different radius and thickness were adopted to conduct harmonic analysis. The effects of PZT shape on shear stresses and optimal frequencies were obtained. Simultaneously, the average shear stresses at the ice/substrate interface and total energy density needed for deicing were calculated. Then, a coefficient named deicing efficiency factor (DEF) was proposed to estimate deicing efficiency. Based on these results, the optimized configuration and deicing frequency are given. Furthermore, four different icing cases for the optimize configuration were studied to further verify the rationality of DEF. The effects of shear stress distributions on deicing efficiency were also analyzed. At same time, a cohesive zone model (CZM) was introduced to describe interface behavior of the plate and ice layer. Standard-explicit co-simulation was utilized to model the wave propagation and ice layer delamination process. Finally, the deicing experiments were carried out to validate the feasibility and correctness of the deicing system.

scholarly journals An Improved Cohesive Zone Model for Interface Mixed-Mode Fractures of Railway Slab Tracks

2021 ◽  
Vol 11 (1) ◽  
pp. 456
Author(s):  
Yanglong Zhong ◽  
Liang Gao ◽  
Xiaopei Cai ◽  
Bolun An ◽  
Zhihan Zhang ◽  
...  
Keyword(s):  
Interface Crack ◽  
Cohesive Zone ◽  
Mixed Mode ◽  
Cohesive Zone Model ◽  
Complex Loading ◽  
Bending Test ◽  
Mixed Mode Fracture ◽  
Zone Model ◽  
Slab Track ◽  
Interfacial Cracks

The interface crack of a slab track is a fracture of mixed-mode that experiences a complex loading–unloading–reloading process. A reasonable simulation of the interaction between the layers of slab tracks is the key to studying the interface crack. However, the existing models of interface disease of slab track have problems, such as the stress oscillation of the crack tip and self-repairing, which do not simulate the mixed mode of interface cracks accurately. Aiming at these shortcomings, we propose an improved cohesive zone model combined with an unloading/reloading relationship based on the original Park–Paulino–Roesler (PPR) model in this paper. It is shown that the improved model guaranteed the consistency of the cohesive constitutive model and described the mixed-mode fracture better. This conclusion is based on the assessment of work-of-separation and the simulation of the mixed-mode bending test. Through the test of loading, unloading, and reloading, we observed that the improved unloading/reloading relationship effectively eliminated the issue of self-repairing and preserved all essential features. The proposed model provides a tool for the study of interface cracking mechanism of ballastless tracks and theoretical guidance for the monitoring, maintenance, and repair of layer defects, such as interfacial cracks and slab arches.

scholarly journals Environmental effects on mode II fracture toughness of unidirectional E-glass/vinyl ester laminated composites

2021 ◽  
Vol 28 (1) ◽  
pp. 382-393
Author(s):  
Mazaher Salamt-Talab ◽  
Fatemeh Delzendehrooy ◽  
Alireza Akhavan-Safar ◽  
Mahdi Safari ◽  
Hossein Bahrami-Manesh ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Sulfuric Acid ◽  
Vinyl Ester ◽  
Cohesive Zone Model ◽  
Flexural Modulus ◽  
Mode Ii ◽  
Zone Model ◽  
Sharp Drop ◽  
Mode Ii Fracture ◽  
Mode Ii Fracture Toughness

Abstract In this article, mode II fracture toughness ( G IIc {G}_{\text{IIc}} ) of unidirectional E-glass/vinyl ester composites subjected to sulfuric acid aging is studied at two different temperatures (25 and 90°C). Specimens were manufactured using the hand lay-up method with the [ 0 ] 20 {{[}0]}_{20} stacking sequence. To study the effects of environmental conditions, samples were exposed to 30 wt% sulfuric acid at room temperature (25°C) for 0, 1, 2, 4, and 8 weeks. Some samples were also placed in the same solution but at 90°C and for 3, 6, 9, and 12 days to determine the interlaminar fracture toughness at different aging conditions. Fracture tests were conducted using end notched flexure (ENF) specimens according to ASTM D7905. The results obtained at 25°C showed that mode II fracture toughness increases for the first 2 weeks of aging and then it decreases for the last 8 weeks. It was also found that the flexural modulus changes with the same trend. Based on the results of the specimens aged at 90°C, a sharp drop in fracture toughness and flexural modulus with a significant decrease in maximum load have been observed due to the aging. Finite element simulations were performed using the cohesive zone model (CZM) to predict the global response of the tested beams.

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