scholarly journals Influence of the micro-structure on saturated transverse flow in fibre arrays

2018 ◽  
Vol 52 (18) ◽  
pp. 2463-2475 ◽  
Author(s):  
Frank Gommer ◽  
Andreas Endruweit ◽  
Andrew C Long
Keyword(s):  
Transverse Flow ◽  
Fibre Volume ◽  
Resin Flow ◽  
Flow Front ◽  
Micro Structure ◽  
Fibre Bundles ◽  
Volume Fractions ◽  
Flow Length ◽  
High Fibre ◽  
Micro Structures

This study analyses the influence of the random filament arrangement in fibre bundles on the resin flow behaviour. Transverse steady-state resin flow that occurs behind a liquid resin flow front was simulated numerically through statistically equivalent micro-structures at high-fibre volume fractions, Vf > 0.6, as observed in fibre bundles. The need of applying a minimum gap distance between neighbouring filaments was overcome by automated local mesh refinement. The derived permeability values showed significant scatter. Convergence of these values was determined at a ratio of flow length to filament radius greater than 20 for all three analysed fibre volume fractions. Mean permeabilities were between 6 and 10 times lower than those predicted for a hexagonal fibre array. A statistical model is proposed, which is able to predict the scatter of observed permeabilities based on simple micro-structural descriptors.

A Study on Resin Flow through a Multi-layered Preform in Resin Transfer Molding

2002 ◽  
Vol 10 (7) ◽  
pp. 493-510 ◽  
Author(s):  
D. G. Seong ◽  
K Chung ◽  
T. J. Kang ◽  
J. R. Youn
Keyword(s):  
Resin Transfer Molding ◽  
Mold Filling ◽  
Transverse Flow ◽  
Woven Fabrics ◽  
Weighted Averaging ◽  
Resin Flow ◽  
Flow Front ◽  
Transfer Molding ◽  
Filling Time ◽  
Flow Through

In resin transfer molding, mold filling is governed by the flow of resin through a preform which is considered as an anisotropic porous media. The resin flow is usually described by Darcy's law and the permeability tensor must be obtained for filling analysis. When the preform is composed of more than two layers with different in-plane permeability, effective average permeability should be determined for the flow analysis in the mold. The most frequently used averaging scheme is the weighted averaging scheme, but it does not account for the transverse flow between adjacent layers. A new averaging scheme is suggested to predict the effective average permeability of the multi-layered preform, which accounts for the transverse flow effect. When the flow in the mold is unsaturated, the effective average permeability is predicted by using the predicted mold filling time and transverse permeability. The new scheme is verified by measuring the effective permeability of the multi-layered preforms which consist of glass fiber random mats, carbon fiber woven fabrics, aramid fiber woven fabrics. Fluid flow through the preform composed of more than two layers with different in-plane permeability shows different flow fronts between layers. The difference in the flow front advancement is observed with a digital camcorder. The predicted flow front is compared with the experimental results and shows a good agreement. It is expected that the effective average permeability can be used for modeling the resin flow through the multi-layered preform.

scholarly journals 3D geometric modelling of discontinuous fibre composites using a force-directed algorithm

2016 ◽  
Vol 51 (17) ◽  
pp. 2389-2406 ◽  
Author(s):  
LT Harper ◽  
CC Qian ◽  
R Luchoo ◽  
NA Warrior
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Current Model ◽  
Tensile Modulus ◽  
Fibre Volume ◽  
Fibre Bundles ◽  
Volume Fractions ◽  
Geometrical Modelling ◽  
Fibre Composites ◽  
Multidimensional Modelling

A geometrical modelling scheme is presented to produce representative architectures for discontinuous fibre composites, enabling downstream modelling of mechanical properties. The model generates realistic random fibre architectures containing high filament count bundles (>3k) and high (∼50%) fibre volume fractions. Fibre bundles are modelled as thin shells using a multidimensional modelling strategy, in which fibre bundles are distributed and compacted to simulate pressure being applied from a matched mould tool. Finite element simulations are performed to benchmark the in-plane mechanical properties obtained from the numerical model against experimental data, with a detailed study presented to evaluate the tensile properties at various fibre volume fractions and specimen thicknesses. Tensile modulus predictions are in close agreement (less than 5% error) with experimental data at volume fractions below 45%. Ultimate tensile strength predictions are within 4.2% of the experimental data at volume fractions between 40 and 55%. This is a significant improvement over existing 2D modelling approaches, as the current model offers increased levels of fidelity, capturing dominant failure mechanisms and the influence of out-of-plane fibres.

scholarly journals A Micro-mechanical Investigation of Empirical Models for the Effective Properties of Aligned Short-Fibre Composites

1995 ◽  
Vol 4 (1) ◽  
pp. 096369359500400
Author(s):  
T.D. Papathanasiou
Keyword(s):  
Aspect Ratio ◽  
Volume Fraction ◽  
Tensile Modulus ◽  
Fibre Volume ◽  
Short Fibre ◽  
Computational Results ◽  
Volume Fractions ◽  
Fibre Composites ◽  
Effective Tensile Modulus ◽  
Fibre Aspect Ratio

The predictions of the Halpin equation concerning the effect of fibre volume fraction and fibre aspect ratio on the effective tensile modulus of uniaxially aligned short-fibre composites are compared with computational experiments on three-dimensional, multiparticle composite samples. The method of boundary elements is used to model the mechanical behaviour of composite specimens consisting of up to 40 discrete aligned fibres randomly dispersed in an elastic matrix. Statistical averages of computational results relating the effective tensile modulus to the aspect ratio and volume fraction of the fibres are found to agree very well with the predictions of the Halpin equation for fibre aspect ratio up to 10 and fibre volume fractions up to 20%. Computational results seem to indicate that the predictions of the Halpin equation fall bellow those of micro-mechanical models at higher volume fractions.

Theoretical study of micro-structure fabrication by multi-beam laser interference lithography with different polarization combinations

2021 ◽  
pp. 2150459
Author(s):  
Xiangxian Wang ◽  
Tianxu Jia ◽  
Jiankai Zhu ◽  
Yingwen Su ◽  
Liping Zhang ◽  
...  
Keyword(s):  
Manufacturing Industry ◽  
Structural Parameters ◽  
Interference Lithography ◽  
Polarization Angle ◽  
Laser Interference Lithography ◽  
Laser Interference ◽  
Micro Structure ◽  
Periodic Patterns ◽  
Beam Laser ◽  
Micro Structures

In this study, we systematically and comprehensively investigated the influence of polarization angle on the fabrication of micro-structures by multi-beam laser interference lithography. Using theoretical analysis and simulation, we studied the effect of different polarization combinations, i.e. transverse electric (TE) and transverse magnetic (TM) polarization combinations, on the characteristics of the micro-structures fabricated by three-, four-, and six-beam laser interference lithography. We successfully obtained micro-structures with different periodic patterns such as honeycomb dots, quasi-elliptic dots, different square dots, and quasi-triangular dots. The simulation results illustrate that polarization affects the formation of interference patterns, pattern contrasts, and periods. The methods discussed herein are simple, low cost, and allow excellent control over structural parameters, and hence are useful for the micro-structure manufacturing industry.

Determination of the Permeability Tensor of Fibrous Reinforcements for VARTM

1999 ◽  
Author(s):  
Pavel B. Nedanov ◽  
Suresh G. Advani ◽  
Shawn W. Walsh ◽  
William O. Ballata
Keyword(s):  
Constant Pressure ◽  
Permeability Tensor ◽  
Three Dimensions ◽  
Resin Flow ◽  
Flow Front ◽  
Resin Impregnation ◽  
Permeable Media ◽  
Front Position ◽  
Transverse Permeability

Abstract VARTM and SCRIMP composite manufacturing processes use a highly permeable media to distribute the resin through the thickness of the composite. Hence, manufacturing simulations of resin flow in such processes requires reliable data for in-plane as well as transverse permeability. The goal of this study is to propose a method for simultaneous determination of the principal values of 3D-permeability tensor of fibrous reinforcements. The permeability components are calculated from experimental data, consisting of flow front position with time during resin impregnation in three dimensions from a radial source under constant pressure using the SMARTweave [Walsh (1993), Fink et al.(1995)] sensor system. Experimental results are compared with numerical simulation.

scholarly journals The Effect of Transcrystalline Interface on the Mechanical Properties of Polyethylene / Polyethylene Composites

2001 ◽  
Vol 10 (2) ◽  
pp. 096369350101000 ◽  
Author(s):  
D. Levitus ◽  
S. Kenig ◽  
M. Kazanci ◽  
H. Harel ◽  
G. Marom
Keyword(s):  
Mechanical Properties ◽  
Fibre Volume ◽  
Experimental Results ◽  
Volume Fractions ◽  
Wide Range ◽  
Longitudinal Strength ◽  
Transcrystalline Layer ◽  
Isothermal Crystallisation ◽  
Positive Effect ◽  
Polyethylene Composites

The effect of the transcrystalline layer on the longitudinal properties of unidirectional polyethylene/polyethylene (PE/PE) composites was studied. Two sets of PE/PE composites were prepared by quenching and by isothermal crystallisation, respectively, using a wide range of fibre volume fractions. Quenching and isothermal crystallisation were expected, respectively, to prevent or to induce generation of a highly ordered transcrystalline layer. The experimental results showed that isothermal crystallisation produced a substantial positive effect on both the longitudinal strength and modulus, which was attributed to transcrystallinity.

scholarly journals Morphological and Chemical Characterization of Titanium and Zirconia Dental Implants with Different Macro- and Micro-Structure

2020 ◽  
Vol 10 (21) ◽  
pp. 7520
Author(s):  
Maria Menini ◽  
Francesco Pera ◽  
Francesco Bagnasco ◽  
Francesca Delucchi ◽  
Elisa Morganti ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Dental Implants ◽  
Chemical Characterization ◽  
Sample Surface ◽  
Titanium Implants ◽  
Good Care ◽  
Micro Structure ◽  
Chemical Residues ◽  
Micro Structures

Background: The aim of this study was to evaluate the macro- and micro-structure and the chemical composition of the surface of 5 different commercially available dental implants. Roughness values were also calculated. Materials and Methods: 1 zirconia implant (NobelPearl of Nobel Biocare) and 4 titanium implants, Syra (Sweden&Martina), Prama (Sweden&Martina), T3 (Biomet 3i), and Shard (Mech&Human), were analyzed through SEM-EDX analysis and quantitative evaluation of surface roughness (1 sample), and XPS chemical analysis (1 sample). Surface roughness was quantitatively assessed using the stereo-SEM method (SSEM). The following area roughness parameters were calculated, according to ISO25178: Sa, Sz, and Sdr. Results: From the SEM observations, all the implants analyzed presented modern well-developed micro-structures as the result of the specific process of double acid etching alone or combined with other additional treatments. Roughness values were generally greater at the level of the implant body and lower at the collar. The chemical characterization of the implant surfaces exhibited excellent results for all of the implants and indicated good care in the production processes. Conclusions: All the samples were well-conceived in terms of topography and surface roughness, and clean in terms of chemical residues.

scholarly journals Fabrication of Micro-Structured Polymer by Micro Injection Molding Based on Precise Micro-Ground Mold Core

Micromachines ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 253 ◽  
Author(s):  
Yanjun Lu ◽  
Fumin Chen ◽  
Xiaoyu Wu ◽  
Chaolan Zhou ◽  
Yan Lou ◽  
...  
Keyword(s):  
Injection Molding ◽  
Mass Production ◽  
Injection Pressure ◽  
Machining Accuracy ◽  
Filling Rate ◽  
Micro Structure ◽  
Micro Injection Molding ◽  
Melt Temperature ◽  
Array Structures ◽  
Micro Structures

Precise micro-grinding machining was proposed to fabricate regular and controllable micro-grooved array structures on the surface of mold cores to realize the mass production and manufacturing of micro-structured polymer components by micro injection molding in this paper. First, the 3D topographies and section profiles of micro-ground mold cores and micro-formed polymers with different micro-structure parameters were presented. Then, the surface roughness of mold cores and polymers were compared. Next, the relationships between machining accuracy of mold core ground by micro-grinding and filling rates of micro-structured polymer formed by micro injection molding were investigated. Finally, the influences of micro injection molding parameters on the filling rate of micro-structures polymer were investigated. It is shown that the micro-structured polymer can be effectively and rapidly fabricated using the proposed method. The experimental results indicate the highest form accuracy of the micro-grooved mold core and the filling rate of micro-structured polymer can reach to 4.05 µm and 99.30%, respectively. It is found that the filling rate of the micro-structured polymer roughly increased with increasing machining accuracy of the mold core. The injection pressure had the greatest influence on the filling rate of the injection formed polymer, while the melt temperature had the least influence.

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