Bounds for Elastic Moduli of Multiphase Short-Fiber Composites

1984 ◽  
Vol 51 (3) ◽  
pp. 540-545 ◽  
Author(s):  
S. Nomura ◽  
T.-W. Chou
Keyword(s):  
Elastic Modulus ◽  
Aspect Ratio ◽  
Correlation Functions ◽  
Volume Fraction ◽  
Perturbation Expansion ◽  
Effective Elastic Modulus ◽  
Fiber Composites ◽  
Short Fiber ◽  
Spherical Particles ◽  
Upper And Lower Bounds

This paper examines upper and lower bounds of the effective elastic modulus of unidirectional short-fiber composites. The short-fibers are modeled by aligned ellipsoidal inclusions of the same aspect ratio but not necessarily the same size. We adopt a perturbation expansion of the composite local strain field by using the Green function tensor. Explicit expressions of the effective elastic modulus are derived up to the third-order term by use of the information on the correlation functions. The variational method is then employed to optimize the bounds of the effective modulus in a closed form. Numerical examples of the bounds as functions of the fiber aspect ratio and the fiber volume fraction are given for a glass/epoxy system. The present approach predicts narrower bounds than those of Hashin and coworkers for the limiting cases of spherical particles and continuous fibers since their bounds corresponds to a model that take the correlation functions up to the second order into account.

Application of Embedded Element in the Short Fiber Reinforced Composite

2018 ◽  
Vol 774 ◽  
pp. 241-246
Author(s):  
Jian Hong Gao ◽  
Xiao Xiang Yang ◽  
Li Hong Huang
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
Element Model ◽  
Short Fiber ◽  
Fiber Reinforced ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite ◽  
Edge Size

The finite element analysis (FEA) is a numerical method for predicting the mechanical property of short fiber reinforced composite usefully. However, as we know, there is always a “jamming” limit when generating fiber architecture expecially in the cases of high volume fraction and high aspect ratio of short fiber. Even if the volume fraction and aspect ratio in finite element model meet the practical requirements, the problem of mesh deformity will always occur which would lead to unconverge of numerical computation. In this work, embedded element technique which will help to reduce the probability of the above two problems is employed to establish the finite element model of short fiber reinforced composite. The effect of edge size, thickness and mesh density of FE models on the elastic modulus were investigated. Numerical results show that the value of elastic modulus mainly depend on the edge size and fiber amount of FE model while the effect of thickness can be neglected. The elastic modulus takes to converge for high element number. An inverse method is proposed to calculate volume fraction of short fibers, by which numerical results agree well with the calculation results of empirical formula based on Halpin-Tsai equation.

Quantitative micro-computed tomography analysis and rheological investigation of Nitrile rubber/Rockwool composites

2021 ◽  
pp. 002199832110338
Author(s):  
Elisson BD da Rocha ◽  
Ana Maria F de Sousa ◽  
Ana Lúcia N da Silva ◽  
Cristina RG Furtado ◽  
Marcos V Colaço ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Elastic Modulus ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
Nitrile Rubber ◽  
Micro Ct ◽  
Micro Computed Tomography ◽  
Rubber Composites ◽  
Ratio Data ◽  
Ct Analysis

This study reports the reinforcement degree investigation of two types of rockwool fibers (F1 and F2), in nitrile rubber composites. The micro-computed tomography (micro-CT) 3D images showed that both fibers were well-dispersed in the NBR matrix, without a preferential orientation. The micro-CT analysis also allowed quantifying volume fraction, inter-fiber distance, and aspect ratio. Those morphometric parameters were used for supporting the composites rheological behavior assessment. Changes in the elastic modulus and phase angle followed the same trend of the inter-fiber distance values, regardless the type of fiber. Both volume fraction and aspect ratio data from the micro-CT analysis were used to predict theoretical values of elastic modulus using the Guth-Gold and modified Guth-Gold equations, and the results obtained were compared to the rheological experimental data. This analysis was helpful to better understand the rockwool fibers reinforcement degree differences in the production of the nitrile rubber composites.

Can the Strength of Brittle Materials be Enhanced?

1992 ◽  
Vol 291 ◽  
Author(s):  
L. Monette ◽  
M. P. Anderson ◽  
G. S. Grest
Keyword(s):  
Computer Model ◽  
Random Distribution ◽  
Load Transfer ◽  
Volume Fraction ◽  
Fiber Composites ◽  
Short Fiber ◽  
Particulate Composites ◽  
Second Phase ◽  
Two Dimensional ◽  
Fiber Volume

ABSTRACTWe have employed a two-dimensional computer model to study the effect of volume fraction of second phase constituents on load transfer (stiffness) and strength in brittle short-fiber composites, i.e. composites containing a random distribution of aligned fibers, and brittle particulate composites. We find that the efficiency of load transfer to the second phase consituent increases with volume fraction in particulate composites, while it decreases for short-fiber composites. The strength of brittle particulate composites is found to decrease, while the strength of brittle short-fiber composites marginally increases only at fiber volume fractions equal or greater than 0.25.

scholarly journals An Estimation Approach for the Effective Elastic Modulus of Lightweight Bulk Filling Material with Compressible Inclusions and Imperfect Interfaces

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3563 ◽  
Author(s):  
Chengxuan Li ◽  
Jianguo Wang ◽  
Fakai Dou
Keyword(s):  
Elastic Modulus ◽  
Volume Fraction ◽  
Effective Elastic Modulus ◽  
Confining Pressure ◽  
Imperfect Interface ◽  
Expanded Polystyrene ◽  
Filling Material ◽  
Curing Time ◽  
Elastic Interface ◽  
Reinforced Clay

In this study, an approach is developed to estimate the density and effective elastic modulus of a lightweight bulk filling material made up of expanded polystyrene (EPS) and cement-reinforced clay (matrix). First, a representative volume element (RVE) is composed of cell A (an EPS and matrix) and cell B (matrix only). Then, an elastic interface is introduced to describe the discontinuity of displacement at the interface between EPS beads and matrix. Third, an Eshelby compliance tensor is modified in cell A to include the effects of imperfect interface and the compressibility of EPS beads. Finally, the approach for the density and effective elastic modulus of the EPS beads mixed cement-reinforced clay is verified with experimental data. The compressibility ratio of lightweight clay is compared under different confining pressures and curing times. It is found that the imperfect interface has salient impacts on the effective elastic modulus with the increase of volume fraction of inclusions. The interface parameters (α and β) vary with curing time and confining pressure. At the same curing time, the parameter α is almost constant regardless of confining pressure but the parameter β changes with confining pressure. The compressibility ratio is smaller for longer curing time if the confining pressure is constant.

A New Theory for the Debonding of Discontinuous Fibers in an Elastic Matrix

1989 ◽  
Vol 170 ◽  
Author(s):  
Christopher K. Y. Leung ◽  
Victor C. Li
Keyword(s):  
Fiber Length ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Interfacial Strength ◽  
Fiber Composites ◽  
Short Fiber ◽  
Fiber Volume ◽  
Physical Reason ◽  
Pull Out

AbstractThe mechanical properties of fiber composites are strongly influenced by the debonding of fibers. When an embedded fiber is loaded from one end, debonding can occur at both the loaded end and the embedded end. Existing theories neglect the possibility of debonding from the embedded end and are thus limited in applications to cases with low fiber volume fraction, low fiber modulus, high interfacial strength/interfacial friction ratio or short fiber length. A new twoway fiber debonding theory, which can extend the validity of one-way debonding theories to all general cases, has recently been developed. In this paper, the physical reason for the occurrence of two-way debonding is discussed. The limit of validity for one-way debonding theories is considered. One-way and two-way debonding theories are then compared with respect to the prediction of composite behaviour. The determination of interfacial parameters from the fiber pull-out test will also be described.

scholarly journals Buckling Analysis of Composite Cylindrical Shells Reinforced by Carbon Nanotubes

2012 ◽  
Vol 59 (4) ◽  
pp. 413-434 ◽  
Author(s):  
Jafar Eskandari Jam ◽  
Esmail Asadi
Keyword(s):  
Carbon Nanotubes ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
Cylindrical Shells ◽  
Ritz Method ◽  
Orientation Angle ◽  
Effective Elastic Modulus ◽  
Buckling Load ◽  
Critical Buckling Load ◽  
Compressive Axial Load

In this paper, the authors investigate a cylindrical shell reinforced by carbon nanotubes. The critical buckling load is calculated using analytical method when it is subjected to compressive axial load. The Mori-Tanaka method is firstly utilized to estimate the effective elastic modulus of composites having aligned oriented straight CNTs. The eigenvalues of the problem are obtained by means of an analytical approach based on the optimized Rayleigh-Ritz method. There is presented a study on the effects of CNTs volume fraction, thickness and aspect ratio of the shell, CNTs orientation angle, and the type of supports on the buckling load of cylindrical shells. Furthermore the effect of CNTs agglomeration is investigated when CNTs are dispersed none uniformly in the polymer matrix. It is shown that when the CNTs are arranged in 90_ direction, the highest critical buckling load appears. Also, the results are plotted for different longitudinal and circumferential mode numbers. There is a specific value for aspect ratio of the cylinder that minimizes the buckling load. The results reveal that for very low CNTs volume fractions, the volume fraction of inclusions has no important effect on the critical buckling load.

Can the maximum volume fraction ensure optimum reinforcement in short‐fiber composites?

2019 ◽  
Vol 136 (31) ◽  
pp. 47821
Author(s):  
Florencia Cruces ◽  
María Guadalupe García ◽  
Nelio Ariel Ochoa
Keyword(s):  
Volume Fraction ◽  
Fiber Composites ◽  
Short Fiber ◽  
Maximum Volume ◽  
Optimum Reinforcement ◽  
Maximum Volume Fraction
Sign in / Sign up

Export Citation Format

Share Document