A meso-scale unit-cell based material model for the single-ply flexible-fabric armor

This paper deals with investigating the tensile characteristics of biaxial weft-knitted reinforced composites in terms of stiffness, strength and failure mechanism. The biaxial weft-knitted fabric was produced on an electronic flat knitting machine by E-glass yarns and then was impregnated with epoxy resin. Using an accurate geometrical model, the composite unit cell was designed in Abaqus software’s environment. Tensile tests were simulated in different directions on the created unit cell and the stiffness was calculated. By applying the proper failure theories, the composite strength was predicted and then critical regions of the unit cell were determined. In the next step, a micromechanical approach was also applied to estimate the same tensile features. Failure theories were also applied to predict the strength and most susceptible areas for failure phenomenon in the composite unit cell. The tensile properties of the produced composites were measured and compared with outputs of the finite element and micromechanical approaches. The results showed that the meso-scale finite element analysis approach can well predict the composite strength. In contrast, the meso-scale analytical equation model was not able to predict it acceptably because this model ignores the strain concentration. Both meso-scale finite element analysis and meso-scale analytical equation approaches predicted the similar locations for the composite failure in wale and course directions.

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Development of a Meso-Scale Material Model for Ballistic Fabric and Its Use in Flexible-Armor Protection Systems

Journal of Materials Engineering and Performance ◽

10.1007/s11665-009-9419-5 ◽

2009 ◽

Vol 19 (1) ◽

pp. 22-39 ◽

Cited By ~ 41

Author(s):

M. Grujicic ◽

W. C. Bell ◽

G. Arakere ◽

T. He ◽

X. Xie ◽

...

Keyword(s):

Material Model ◽

Protection Systems ◽

Flexible Armor ◽

Meso Scale

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A macroscopic material model for woven fabrics based on mesoscopic sawtooth unit cell

Composite Structures ◽

10.1016/j.compstruct.2017.08.031 ◽

2017 ◽

Vol 180 ◽

pp. 531-541 ◽

Cited By ~ 3

Author(s):

Ozan Erol ◽

Brian M. Powers ◽

Michael Keefe

Keyword(s):

Material Model ◽

Woven Fabrics ◽

Unit Cell

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Acoustic Non-Reciprocity in Lattices With Nonlinearity, Internal Hierarchy, and Asymmetry: Computational Study

Journal of Vibration and Acoustics ◽

10.1115/1.4043783 ◽

2019 ◽

Vol 141 (5) ◽

Cited By ~ 6

Author(s):

Matthew D. Fronk ◽

Sameh Tawfick ◽

Chiara Daraio ◽

Shuangbao Li ◽

Alexander Vakakis ◽

...

Keyword(s):

Wave Propagation ◽

Linear Time ◽

Lattice Structure ◽

Computational Study ◽

Unit Cell ◽

Linear Time Invariant ◽

Scale Unit ◽

Unit Cells ◽

Linear Time Invariant Systems ◽

System Properties

Reciprocity is a property of linear, time-invariant systems whereby the energy transmission from a source to a receiver is unchanged after exchanging the source and receiver. Nonreciprocity violates this property and can be introduced to systems if time-reversal symmetry and/or parity symmetry is lost. While many studies have induced nonreciprocity by active means, i.e., odd-symmetric external biases or time variation of system properties, considerably less attention has been given to acoustical structures that passively break reciprocity. This study presents a lattice structure with strong stiffness nonlinearities, internal scale hierarchy, and asymmetry that breaks acoustic reciprocity. Macroscopically, the structure exhibits periodicity yet asymmetry exists in its unit cell design. A theoretical study, supported by experimental validation, of a two-scale unit cell has revealed that reciprocity is broken locally, i.e., within a single unit cell of the lattice. In this work, global breaking of reciprocity in the entire lattice structure is theoretically analyzed by studying wave propagation in the periodic arrangement of unit cells. Under both narrowband and broadband excitation, the structure exhibits highly asymmetrical wave propagation, and hence a global breaking of acoustic reciprocity. Interpreting the numerical results for varying impulse amplitude, as well as varying harmonic forcing amplitude and frequency/wavenumber, provides strong evidence that transient resonant capture is the driving force behind the global breaking of reciprocity in the periodic structure. In a companion work, some of the theoretical results presented herein are experimentally validated with a lattice composed of two-scale unit cells under impulsive excitation.

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A Non-Orthogonal Constitutive Material Model for Advanced Woven Fabrics Based on a Mesoscale Unit Cell

Volume 9: Mechanics of Solids, Structures and Fluids; NDE, Diagnosis, and Prognosis ◽

10.1115/imece2016-65747 ◽

2016 ◽

Cited By ~ 1

Author(s):

Ozan Erol ◽

Brian M. Powers ◽

Michael Keefe

Keyword(s):

Mechanical Behavior ◽

Mechanical Response ◽

Material Model ◽

Shear Resistance ◽

Woven Fabrics ◽

Unit Cell ◽

Uniaxial Tensile ◽

Constitutive Material Model ◽

Proposed Model ◽

Constitutive Material

Advanced woven fabrics can provide a wide range of mechanical properties since the yarns can be arranged in different architectural patterns thus allowing the fabric structure to be tuned based on the specific needs. This adjustable nature makes them an attractive material choice for applications where versatility is highly desired. Hence, there is an increasing interest in woven fabrics in the recent years. They have been used in various applications such as deployable structures, protective garments, medical scaffolds and composites. With the increased interest, there is a need for efficient and accurate computational tools to investigate the mechanical behavior and deformation of woven fabrics for specific applications. Although there are several computational models in the literature that can model uniaxial and biaxial behavior of woven fabrics, there are not any commonly accepted material models for woven fabrics due to the complex interaction of trellising and deformation. Here, we propose an easy to implement constitutive material model based on a mesoscale unit cell of the woven fabrics. The proposed model utilizes the two prominent deformation mechanisms affecting the mechanical response at the mesoscale level: (1) Yarn stretching, and (2) shearing. These mesoscale mechanisms are mechanistically implemented within an unit cell by using truss and rotational springs to generate the mechanical response of the woven fabric. The yarns’ nonlinear mechanical behavior is modeled with non-linear trusses and assumed to be pin-jointed at the center of the unit cell. The truss elements are allowed to rotate at the pin-joint reproducing the yarns’ relative rotational motion during shearing. The fabric’s shear resistance involves two components: yarn-to-yarn relative rotation/sliding and yarn locking due to the yarn transverse compression. These components of the fabric shear resistance are modeled as a non-linear rotational spring located at the pin-joint which generates a moment resisting the shear deformation. The developed forces and moments from the trusses and rotational spring within the unit cell structure are then used to determine the continuum stress state of the material point. The material properties and parameters defined in the proposed model are easy to obtain from uniaxial tensile and shear tests on fabrics. To validate the material model, plain weave Kevlar KM2 fabric is modeled by replicating the standard uniaxial tensile and bias extension tests. The results obtained show that the material model provides a good description of the in-plane deformation and mechanical response.

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An Approach for Material Model Identification of a Composite Coating Using Micro-Indentation and Multi-Scale Simulations

Coatings ◽

10.3390/coatings12010092 ◽

2022 ◽

Vol 12 (1) ◽

pp. 92

Author(s):

Pouya Shojaei ◽

Riccardo Scazzosi ◽

Mohamed Trabia ◽

Brendan O’Toole ◽

Marco Giglio ◽

...

Keyword(s):

Finite Element ◽

Model Comparison ◽

Plastic Material ◽

Composite Coatings ◽

Material Model ◽

Scale Model ◽

Indentation Testing ◽

Micro Scale ◽

Micro Indentation ◽

Meso Scale

While deposited thin film coatings can help enhance surface characteristics such as hardness and friction, their effective incorporation in product design is restricted by the limited understanding of their mechanical behavior. To address this, an approach combining micro-indentation and meso/micro-scale simulations was proposed. In this approach, micro-indentation testing was conducted on both the coating and the substrate. A meso-scale uniaxial compression finite element model was developed to obtain a material model of the coating. This material model was incorporated within an axisymmetric micro-scale model of the coating to simulate the indentation. The proposed approach was applied to a Ti/SiC metal matrix nanocomposite (MMNC) coating, with a 5% weight of SiC nanoparticles deposited over a Ti-6Al-4V substrate using selective laser melting (SLM). Micro-indentation testing was conducted on both the Ti/SiC MMNC coating and the Ti-6Al-4V substrate. The results of the meso-scale finite element indicated that the MMNC coating can be represented using a bi-linear elastic-plastic material model, which was incorporated within an axisymmetric micro-scale model. Comparison of the experimental and micro-scale model results indicated that the proposed approach was effective in capturing the post-indentation behavior of the Ti/SiC MMNC coating. This methodology can also be used for studying the response of composite coatings with different percentages of reinforcements.

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Numerical prediction of the ballistic performance of hygrothermally aged CFRP laminates using a multi-scale modelling approach

EPJ Web of Conferences ◽

10.1051/epjconf/202125003008 ◽

2021 ◽

Vol 250 ◽

pp. 03008

Author(s):

D. Thomson ◽

D. E. Sommer ◽

O. Falcó ◽

G. Quino ◽

H. Cui ◽

...

Keyword(s):

Crack Density ◽

Material Model ◽

Transverse Cracks ◽

Ballistic Performance ◽

Cfrp Laminates ◽

Micro Scale ◽

Multi Scale ◽

Hygrothermal Ageing ◽

Scale Modelling ◽

Meso Scale

A multi-scale modelling strategy is proposed to investigate the potential effects of hygrothermal ageing on the ballistic performance of CFRP laminates. At the micro-scale, damage evolution due to cyclic hygrothermal loads is simulated on a representative microstructure using an adapted fatigue damage law. Then, the results of the micro-mechanical analysis are used to measure the predicted transverse crack density and calibrate a meso-scale material model with the effects of micro-scale damage. Finally, a meso-scale impact model is generated with seeded transverse cracks at the predicted crack density and the calibrated material properties from the homogenisation step, which allows for the performance of the laminate to be compared at different stages of hygrothermal ageing damage.

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