Matrix Cracking in Fiber-Reinforced Composite Materials

1991 ◽  
Vol 58 (3) ◽  
pp. 846-848 ◽  
Author(s):  
H. A. Luo ◽  
Y. Chen
Keyword(s):  
Composite Materials ◽  
Volume Fraction ◽  
Matrix Material ◽  
Homogeneous Medium ◽  
Circular Inclusion ◽  
Matrix Cracking ◽  
Phase Model ◽  
Infinite Matrix ◽  
Finite Concentration ◽  
Three Phase

Matrix cracking is a major pattern of the failure of composite materials. A crack can form in the matrix during manufacturing, or be produced during loading. Erdogan, Gupta, and Ratwani (1974) first considered the interaction between an isolated circular inclusion and a line crack embedded in infinite matrix. As commented by Erdogan et al., their model is applicable to the composite materials which contain sparsely distributed inclusions. For composites filled with finite concentration of inclusions, it is commonly understood that the stress and strain fields near the crack depend considerably on the microstructure around it. One notable simplified model is the so-called three-phase model which was introduced by Christensen and Lo (1979). The three-phase model considers that in the immediate neighborhood of the inclusion there is a layer of matrix material, but at certain distance the heterogeneous medium can be substituted by a homogeneous medium with the equivalent properties of the composite. Thus, for the problems of which the interest is in the field near the inclusion, it can reasonably be accepted as a good model. The two-dimensional version of the three-phase model consists of three concentric cylindrical layers with the outer one, labeled by 3, extended to infinity. The external radii a and b of the inner and intermediate phases, labeled by 1 and 2, respectively, are related by (a/b)2 =c, where c is the volume fraction of the fiber in composite.

Effective Property Estimation of CMC Minicomposites Considering Porosity

2018 ◽  
Author(s):  
Abhilash M. Nagaraja ◽  
Suhasini Gururaja
Keyword(s):  
Elastic Properties ◽  
Volume Fraction ◽  
Matrix Material ◽  
Ceramic Matrix Composites ◽  
Unit Cell ◽  
Matrix Cracking ◽  
Failure Behavior ◽  
Numerical Homogenization ◽  
Element Analysis ◽  
Micro Scale

Ceramic matrix composites (CMCs) are a promising subclass of composite materials suitable for high temperature applications. CMCs exhibit multiple damage mechanisms such as matrix cracking, interphase debonding, fiber sliding, fiber pullout, delaminations etc. Additionally, process induced defects such as matrix porosity exists at multiple length scales and has a considerable influence on the mechanical and failure behavior of CMCs. In the current work, the effect of intra-tow porosity, which exist at the micro-scale, on the mechanical behavior of CMCs has been investigated by numerical homogenization. Micro-scale response of 3 phase CMCs with intra tow pores has been obtained by finite element analysis based homogenization. Pores have been modeled as non-intersecting ellipsoids in a square unit cell representative of matrix material. The effective mechanical properties of porous matrix at the micro scale has been obtained from numerical homogenization, which are in good agreement with Mori-Tanaka mean field theory. The obtained matrix elastic properties have then been included in a three phase unit cell consisting of fiber, interphase and matrix representative of CMC microstructure. The effect of porosity volume fraction and aspect ratio on the effective elastic properties of the composite have been reported. Homogenization approach to model statistical distribution of pore size obtained from X-ray computed tomography of CMC minicomposite has been proposed.

scholarly journals Comparison Between Confined and Unconfined Laser Peening Effect on the Fatigue Life of Composite Materials

2020 ◽  
pp. 1657-1664
Author(s):  
Ahmed N. Al- Khazraji ◽  
Ammar A. Mutasher
Keyword(s):  
Composite Materials ◽  
Endurance Limit ◽  
Volume Fraction ◽  
Unsaturated Polyester ◽  
Matrix Material ◽  
Laser Peening ◽  
Black Paint ◽  
Micro Particles ◽  
The Difference ◽  
Shock Peening

Mechanical Engineering Department/ University of Technology- Baghdad. Confinement layer is considered as the most important parameter during the laser shock peening (LSP) treatment.  In this paper, its effect on the surface treatment effectivity of composite materials was investigated. The composite used in this research was fabricated using hand lay-up as a manufacturing process. The matrix material was built from unsaturated polyester resin and reinforced with 2.5% volume fraction of micro particles of aluminum powder. Fatigue test was conducted at room temperature with constant amplitude stress and a stress ratio of R =-1, before and after LSP treatment. LSP was applied with and without confinement layer at the same level of energy after the specimens were coated with a black paint. The results manifested that the laser peening without confinement layer increased the endurance limit by about 13.296% compared with the untreated state. Whereas using water as a confinement layer during treatment reduced the endurance strength by about 18.133% compared to the untreated state. Also, it was observed that the difference between confined and unconfined LSP effects on the endurance limit was about 31.429%.

scholarly journals Tissue Anisotropy Modeling Using Soft Composite Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Arnab Chanda ◽  
Christian Callaway
Keyword(s):  
Composite Materials ◽  
Mechanical Behavior ◽  
Soft Tissues ◽  
Volume Fraction ◽  
Matrix Material ◽  
Testing Machine ◽  
The Body ◽  
Three Dimensions ◽  
Tissue Anisotropy ◽  
Soft Composite

Soft tissues in general exhibit anisotropic mechanical behavior, which varies in three dimensions based on the location of the tissue in the body. In the past, there have been few attempts to numerically model tissue anisotropy using composite-based formulations (involving fibers embedded within a matrix material). However, so far, tissue anisotropy has not been modeled experimentally. In the current work, novel elastomer-based soft composite materials were developed in the form of experimental test coupons, to model the macroscopic anisotropy in tissue mechanical properties. A soft elastomer matrix was fabricated, and fibers made of a stiffer elastomer material were embedded within the matrix material to generate the test coupons. The coupons were tested on a mechanical testing machine, and the resulting stress-versus-stretch responses were studied. The fiber volume fraction (FVF), fiber spacing, and orientations were varied to estimate the changes in the mechanical responses. The mechanical behavior of the soft composites was characterized using hyperelastic material models such as Mooney-Rivlin’s, Humphrey’s, and Veronda-Westmann’s model and also compared with the anisotropic mechanical behavior of the human skin, pelvic tissues, and brain tissues. This work lays the foundation for the experimental modelling of tissue anisotropy, which combined with microscopic studies on tissues can lead to refinements in the simulation of localized fiber distribution and orientations, and enable the development of biofidelic anisotropic tissue phantom materials for various tissue engineering and testing applications.

On the static and dynamic properties of fiber-reinforced polymer composites

2016 ◽  
Vol 30 (11) ◽  
pp. 1560-1577 ◽  
Author(s):  
Chong Yang Gao ◽  
Jian Zhang Xiao ◽  
Liang Chi Zhang ◽  
Ying Lin Ke
Keyword(s):  
Mechanical Properties ◽  
Polymer Composites ◽  
Volume Fraction ◽  
Fiber Reinforced Polymer ◽  
Phase Model ◽  
Fiber Reinforced ◽  
Reinforced Polymer ◽  
Fiber Reinforced Polymer Composites ◽  
Three Phase ◽  
The Matrix

This article establishes a reliable constitutive model to describe the behaviors of fiber-reinforced polymer composites under quasi-static and dynamic loading. This model integrates the contributions of all the three phases of a composite: the fiber, the matrix, and the fiber/matrix interphase, which make it capable of capturing the key micromechanical effect of the interphase on the macroscopic mechanical properties of composites. The interphase is taken as a transversely isotropic material together with the fiber. By analyzing glass/epoxy and carbon/epoxy composites, it was found that the model predictions agree well with the experimental data and the model is more effective particularly when the fiber volume fraction is high. The dynamic three-phase model was also established by using the coupling of the elastic and Maxwell elements for the viscoelasticity of the matrix as well as the interphase. The article concludes that the three-phase model with consideration of the interphase influence can precisely characterize the static and dynamic mechanical properties of a FRP composite.

scholarly journals Determination of the mechanical properties of 3d-printed polymer products by methods of structural mechanics

2021 ◽  
pp. 16-32
Author(s):  
Vladislav Solovei ◽  
Аnton Karvatskii ◽  
Taras Lazarev ◽  
Іgor Mikulionok ◽  
Iryna Omelchuk
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Modulus Of Elasticity ◽  
Numerical Experiments ◽  
Volume Fraction ◽  
Numerical Models ◽  
Homogeneous Medium ◽  
Polymeric Materials ◽  
Fused Deposition ◽  
Effective Mechanical Properties

Mathematical models of stress-strain state (SSS) for modeling tests of polymer composite samples obtained by fused deposition modeling (FDM) in approximations of isotropic and orthotropic media are formulated. An algorithm for solving the inverse SSS problem to determine the effective mechanical properties in the orthotropic approximation of composite products printed by the FDM method has been developed. Numerical models have been developed to solve inverse SSS problems to determine the effective orthotropic mechanical properties of composite products with different degrees of reinforcement, obtained using additive technologies based on the FDM method. The grid convergence of the developed numerical models by the method of double recalculation is investigated. It is established that the used mesh of geometric models of product samples leads to errors in determining the vector of the modulus of elasticity in the range of 0–3.19%, and the vector of the shear modulus does not exceed 0.05–0.2%. Numerical experiments to determine the effective mechanical properties of samples of composite polymeric materials in the approximation of orthotropic homogeneous medium were performed. The obtained results are compared with the data of calculations by analytical dependences to determine the effective mechanical properties of composite materials. It is shown that the results of numerical studies agree satisfactorily with the corresponding data obtained from analytical dependences in the range of 0.081–5.696%. It is established that all three components of the vectors of modulus of elasticity and shear increase with the degree of reinforcement. The largest increase is observed for the components of vectors  and , which is due to the reinforcement in the direction , and the difference between the values ​​of the components of vectors  and  and  and  is due to the cross-sectional asymmetry of the strand. Dependences for operative prediction of effective orthotropic mechanical properties of composites based on PLA + KEVLAR 29 within the limits of change in the volume fraction of reinforcing fibers up to 5% are obtained. To develop new composite materials with predetermined properties, it is not necessary to perform multivariate, rather complex and cumbersome numerical experiments in solving the inverse SSS problem.

Computational Simulation of Fracture Behavior Due to Mechanical and Constituent Properties of CFCCs

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1724-1729
Author(s):  
Oh Heon Kwon ◽  
Yu Seong Yun
Keyword(s):  
Numerical Simulation ◽  
Fracture Behavior ◽  
Volume Fraction ◽  
Computational Simulation ◽  
Matrix Material ◽  
Ceramic Matrix Composites ◽  
Matrix Cracking ◽  
Fiber Volume ◽  
Element Analysis ◽  
Cracking Stress

Continuous fiber reinforced ceramic matrix composites (CFCCs) are recently a subject of a lot of research interest due to advantages which are high specific stiffness and strength, high toughness and nonbrittle failure as compared to monolithic ceramics. The basic purpose of the present study is to describe graphically the fracture behavior of CFCCs according to a dependence on constituent properties. In CFCCs, following matrix cracking, intact fibers bridge effects impose closure tractions behind the crack tip that reduce the driving force for further cracking. Thus matrix cracking stress and bridging stress are important. Then the change of fiber volume fraction is given for the matrix cracking stress by the numerical simulation. Numerical simulation are carried out by using a finite element analysis code ANSYS. The double mesh concept is applied to account for fiber and matrix material properties.

scholarly journals 3D Modelling of Mass Transfer into Bio-Composite

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2257
Author(s):  
Marouane Kabbej ◽  
Valérie Guillard ◽  
Hélène Angellier-Coussy ◽  
Caroline Wolf ◽  
Nathalie Gontard ◽  
...  
Keyword(s):  
Relative Permeability ◽  
Volume Fraction ◽  
Water Vapor Permeability ◽  
High Volume ◽  
Phase Model ◽  
Vapor Permeability ◽  
Three Dimensional Model ◽  
Two Phase ◽  
Phase Structures ◽  
Three Phase

A three-dimensional model structure that allows considering interphase layer around permeable inclusions is developed to predict water vapor permeability in composite materials made of a matrix Poly(3-HydroxyButyrate-co-3-HydroxyValerate) (PHBV) including Wheat Straw Fiber (WSF) particles. About 500 two-phase structures corresponding to composites of different particles volume fractions (5.14−11.4−19.52 % v/v) generated using experimental particles’ size distribution have permitted to capture all the variability of the experimental material. These structures have served as a basis to create three-phase structures including interphase zone of altered polymer property surrounding each particle. Finite Element Method (FEM) applied on these structures has permitted to calculate the relative permeability (ratio between composite and neat matrix permeability P/Pm). The numerical results of the two-phase model are consistent with the experimental data for volume fraction lower than 11.4 %v/v but the large upturn of the experimental relative permeability for highest volume fraction is not well represented by the two-phase model. Among hypothesis made to explain model’s deviation, the presence of an interphase with its own transfer properties is numerically tested: numerical exploration made with the three-phase model proves that an interphase of 5 µm thick, with diffusivity of Di ≥ 1 × 10−10 m2.s−1, would explain the large upturn of permeability at high volume fraction.

Transport of organochlorine pesticides in soil columns enhanced by dissolved organic carbon

1997 ◽  
Vol 35 (7) ◽  
pp. 139-145 ◽  
Author(s):  
Jiann-Yuan Ding ◽  
Shian-Chee Wu
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Organochlorine Pesticides ◽  
Transport Model ◽  
Phase Model ◽  
Soil Columns ◽  
Two Phase ◽  
Three Phase ◽  
Phase Transport ◽  
Remediation Of Soil

The objective of this study is to quantify the effects of humic acid solution infiltration on the transport of organochlorine pesticides (OCPs) in soil columns using a three-phase transport model. From experimental results, it is found that the dissolved organic carbon enhances the transport of OCPs in the soil columns. In the OCPs-only column, the concentration profiles of OCPs can be simulated well using a two-phase transport model with numerical method or analytical solution. In the OCPs-DOC column, the migrations of aldrin, DDT and its daughter compounds are faster than those in the OCPs-only column. The simulation with the three-phase model is more accurate than that with the two-phase model. In addition, significant decrease of the fluid pore velocities of the OCPs-DOC column was found. When DOC leachate is applied for remediation of soil or groundwater pollution, the decrease of mean pore velocities will be a crucial affecting factor.

scholarly journals Autocratisation by Term Limits Manipulation in Sub-Saharan Africa

2020 ◽  
Vol 55 (3) ◽  
pp. 228-250 ◽  
Author(s):  
Andrea Cassani
Keyword(s):  
Comparative Studies ◽  
Political Competition ◽  
Chief Executive ◽  
Term Limits ◽  
Sub Saharan Africa ◽  
Phase Model ◽  
Econometric Modelling ◽  
Three Phase ◽  
Sub Saharan ◽  
Personal Rule

Besides the introduction of multi-party elections, the sub-Saharan wave of democratic reforms of the 1990s encompassed the introduction of limits to the number of terms that a chief executive can serve. Executive term limits (ETLs) are key for democracy to advance in a continent with a legacy of personal rule. However, the manipulation of ETLs has become a recurring mode of autocratisation, through which African aspiring over-stayers weaken executive constraints, taint political competition, and limit citizens’ possibility to choose who governs. This article presents a three-phase model of autocratisation by ETL manipulation and, using new data, offers one of the first regional comparative studies of ETL manipulation in sub-Saharan Africa that rests on econometric modelling. The analysis leads to revisiting some previous findings on the drivers of ETL manipulation and highlights the relevance of other previously underestimated factors that may either discourage a leader from challenging ETLs or prevent their successful manipulation.

scholarly journals Application of Artificial Intelligence and Gamma Attenuation Techniques for Predicting Gas–Oil–Water Volume Fraction in Annular Regime of Three-Phase Flow Independent of Oil Pipeline’s Scale Layer

Mathematics ◽  
2021 ◽  
Vol 9 (13) ◽  
pp. 1460
Author(s):  
Abdulaziz S. Alkabaa ◽  
Ehsan Nazemi ◽  
Osman Taylan ◽  
El Mostafa Kalmoun
Keyword(s):  
Gamma Radiation ◽  
Volume Fraction ◽  
Phase Flow ◽  
Gas Oil ◽  
Oil Pipeline ◽  
Intelligent Technique ◽  
Scale Layer ◽  
Three Phase ◽  
Three Phase Flow ◽  
Annular Regime

To the best knowledge of the authors, in former studies in the field of measuring volume fraction of gas, oil, and water components in a three-phase flow using gamma radiation technique, the existence of a scale layer has not been considered. The formed scale layer usually has a higher density in comparison to the fluid flow inside the oil pipeline, which can lead to high photon attenuation and, consequently, reduce the measuring precision of three-phase flow meter. The purpose of this study is to present an intelligent gamma radiation-based, nondestructive technique with the ability to measure volume fraction of gas, oil, and water components in the annular regime of a three-phase flow independent of the scale layer. Since, in this problem, there are several unknown parameters, such as gas, oil, and water components with different amounts and densities and scale layers with different thicknesses, it is not possible to measure the volume fraction using a conventional gamma radiation system. In this study, a system including a 241Am-133Ba dual energy source and two transmission detectors was used. The first detector was located diametrically in front of the source. For the second detector, at first, a sensitivity investigation was conducted in order to find the optimum position. The four extracted signals in both detectors (counts under photo peaks of both detectors) were used as inputs of neural network, and volume fractions of gas and oil components were utilized as the outputs. Using the proposed intelligent technique, volume fraction of each component was predicted independent of the barium sulfate scale layer, with a maximum MAE error of 3.66%.

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