Mechanics of random discontinuous long-fiber thermoplastics. Part II: Direct simulation of uniaxial compression

El-Rahman, Ahmed I. Abd; Tucker, Charles L.

doi:10.1122/1.4818804

Cited by 25 publications

(21 citation statements)

References 24 publications

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“…Specifically, we use the general contact algorithm in Abaqus [25]. El-Rahman et al [26] also used the general contact algorithm to simulate compressive behavior of random fiber assemblies. The contact between two inclusion surfaces may occur in two directions-one normal to the surfaces and one tangential to the surfaces.…”

Section: Packed Inclusion Assembly Generationmentioning

confidence: 99%

Microstructure modeling of random composites with cylindrical inclusions having high volume fraction and broad aspect ratio distribution

Islam

Tudryn

Picu

2016

Computational Materials Science

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This paper presents a computational methodology for generating microstructure models of random composites with cylindrical or sphero-cylindrical inclusions having high volume fraction and broad aspect ratio distribution. The proposed methodology couples the random sequential adsorption (RSA) algorithm and dynamic finite element (FE) simulations. It uses RSA to generate sparse inclusion assemblies of low volume fraction and subsequently utilizes dynamic FE simulation for inclusion packing to achieve high volume fractions. The method can generate RVEs with volume fraction as high as 50% depending on the inclusion aspect ratio. Its capability is demonstrated by generating three distinct types of models with different inclusion characteristics which are further characterized in terms of homogeneity and isotropy. The results indicate that the proposed method is capable of generating models with low spatial variability of the filler orientation and volume fraction. The method can be used to generate input configurations for continuum and discrete representations of such random media.

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Section: Packed Inclusion Assembly Generationmentioning

confidence: 99%

Microstructure modeling of random composites with cylindrical inclusions having high volume fraction and broad aspect ratio distribution

Islam

Tudryn

Picu

2016

Computational Materials Science

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“…However, they utilize the drag of prolate spheroids, which leads to a total drag force on a fiber that depends on discretization [25]. Direct models have been utilized in representative volume elements to determine rheological properties [26,27], contact properties in microstructures [28] and parameters of macroscopic fiber orientation models [21]. This approach of "computational rheometry" has also been applied to SMC represented as a planar network of fiber bundles that interact through local shear forces at contact points [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Direct Bundle Simulation approach for the compression molding process of Sheet Molding Compound

Meyer

Schöttl

Bretz

et al. 2020

Composites Part A: Applied Science and Manufacturing

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The manufacturing process of Sheet Molding Compounds (SMC) induces a reorientation of fibers during the flow, which influences local properties and is of interest for structural computations. Typically, the reorientation is described with an evolution equation for the second order fiber orientation tensor, which requires a closure approximation and multiple empirical parameters to describe long fibers. However, CT scans of SMC microstructures show that fiber bundles stay mostly intact during molding. Treating hundreds of fibers in such a bundle as one instance enables direct simulation on component scale. This work proposes a direct simulation approach, in which bundle segments experience Stokes' drag forces and opposing forces are applied to the fluid field. The method is applied to specimens with a double-curved geometry and compared to CT scans. The Direct Bundle Simulation provides increased accuracy of fiber orientations and enables prediction of fiber-matrix separation with affordable computational effort at component scale.

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“…Detailed flowcharts of the RSA and the modified contraction model steps are given in Appendices A and B. This resulting dataset is used for the microstructural characterization in the following section and further in the packing stress calculation [8]. Additional details regarding the numerical constructions and implementations of the generation models are given in Ref.…”

Section: Modified Mechanical Contractionmentioning

confidence: 99%

Mechanics of Random Discontinuous Long-Fiber Thermoplastics—Part I: Generation and Characterization of Initial Geometry

El-Rahman

Tucker

2013

Journal of Applied Mechanics

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The deformation mechanics of dry networks of large-aspect-ratio fibers with random orientation controls the processing of long-fiber thermoplastics (LFTs) and greatly affects the mechanical properties of the final composites. Here, we generate initial geometries of fiber networks in a cubic unit cell with a fiber aspect ratio of lid =100 and fully periodic boundary conditions for later numerical simulation. The irreversible random sequential adsorption (RSA) process is first used to generate a quasi-random structure due to the excluded-volume requirements. In order to investigate the nonequilibrium character of the RSA, a second method, which is similar to the mechanical contraction method (MCM) (Williams and Philipse, 2003, "Random Packings of Spheres and Spherocylinders Simulated by Mechanical Contraction," Phys, Rev, E, 67, pp. 1-9) and based on a simplified Metropolis Monte Carlo (MC) simulation is then developed to produce quasiequilibrium fiber geometries. The RSA packing results (4>K4.423% when using a fiber aspect ratio of ¡00) are in good agreement with the maximum unforced random packing limits (Evans and Gibson, 1986, "Prediction of the Maximum Packing Eraction Achievable in Randomly Oriented " Compos. Sei. TechnoL, 25,. The fiber structures were characterized by several distribution functions, including pair-spatial and pair-orientation distributions, based on either the center-tocenter distance or the shortest distance between the particles. The results show that the structures generated by the RSA have an easily-detectable long-range spatial correlation but very little orientational correlation. In contrast, the quasi-equilibrium structures have reduced spatial correlation but increased short-range orientational correlation

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Mechanics of random discontinuous long-fiber thermoplastics. Part II: Direct simulation of uniaxial compression

Cited by 25 publications

References 24 publications

Microstructure modeling of random composites with cylindrical inclusions having high volume fraction and broad aspect ratio distribution

Microstructure modeling of random composites with cylindrical inclusions having high volume fraction and broad aspect ratio distribution

Direct Bundle Simulation approach for the compression molding process of Sheet Molding Compound

Mechanics of Random Discontinuous Long-Fiber Thermoplastics—Part I: Generation and Characterization of Initial Geometry

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