Effective Medium of Unidirectional Short-Fiber Composites by a Self-Consistent Method

1987 ◽  
Vol 109 (1) ◽  
pp. 64-66
Author(s):  
Seiichi Nomura
Keyword(s):  
Fiber Composite ◽  
Homogeneous Medium ◽  
Fiber Composites ◽  
Short Fiber ◽  
Effective Medium ◽  
Matrix Phase ◽  
Effective Stiffness ◽  
Self Consistent ◽  
The Matrix ◽  
Consistent Method

A new self-consistent method is proposed to calculate the effective stiffness of unidirectional short-fiber composites where each transversely-isotropic short-fibers is embedded in an infinite homogeneous matrix phase. The equilibrium equation for the elastic field in short-fiber composite materials is converted into an integro-differential equation using the Green’s function for a homogeneous medium. The “effective medium” is chosen in such a way that the ensemble averaged strain field for the composite is equal to that of the homogeneous medium that exhibits the same overall response as the composite. The “effective stiffness” and the “effective mass density” are defined as those properties of the effective medium. The obtained expression for the effective stiffness is new and is not symmetrical with the matrix phase and the fiber phase, thus, reflecting the matrix role more properly than previous works which gave symmetrical results. The result is also favorably compared with experimental data.

Effective Medium Approach to Matrix-Inclusion Type Composite Materials

1987 ◽  
Vol 54 (4) ◽  
pp. 880-883 ◽  
Author(s):  
S. Nomura
Keyword(s):  
Displacement Field ◽  
Mass Density ◽  
Spherical Inclusion ◽  
Homogeneous Medium ◽  
Dynamic Effect ◽  
Effective Medium ◽  
Effective Stiffness ◽  
Inclusion Type ◽  
The Matrix ◽  
Homogenous Medium

This paper addresses a problem of finding the effective medium that exhibits the same overall response as a given composite material reinfored by unidirectional short-fibers (chopped fibers). The expression for the displacement field in composites is obtained by converting the equilibrium equation into an integro-differential equation using the quasi-static Green’s function for a homogeneous medium. The “effective medium” is chosen that the ensemble averaged displacement field for the composite is equal to that of an equivalent homogenous medium. The “effective stiffness” and the “effective mass density” are defined as those properties of the effective medium. This is a first preliminary attempt to analyze the elasto-dynamic effect of matrix-inclusion type of composites. The obtained result for the effective stiffness is new and is not symmetrical with the interchange of the matrix phase and the fiber phase, unlike previous models. The result is also favorably compared with experimental data for spherical-inclusion reinforced composites.

Study on Enhancement of Mechanical Strength by Knotted Shape Memory Alloy Fiber in TiNi Fiber Composites

2008 ◽  
Vol 385-387 ◽  
pp. 421-424
Author(s):  
Yong Li Zhao ◽  
Jie Li ◽  
Ming Jin
Keyword(s):  
Shape Memory Alloy ◽  
Mechanical Strength ◽  
Shape Memory ◽  
Fiber Composite ◽  
Stress Transfer ◽  
Fiber Composites ◽  
Tension Test ◽  
Fiber Tension ◽  
The Matrix ◽  
Straight Fiber

In this paper, the experimental investigation into the enhancement of mechanical strength in shape memory alloy (SMA) fiber composites is made by using knotted fiber at the two ends instead of straight fiber. TiNi SMA fiber with both ends knotted is used for purpose of better ensuring stress transfer from the matrix to the fiber than straight fiber. Tension test is carried out above the austenitic finish temperature in air. Specimens are heated by means of electrical resistive lamplight heating. The results indicate that the mechanical strength is larger in the knotted fiber composite than in the straight fiber composite. Knotted fiber exerts the superiority of TiNi SMA fiber composite.

scholarly journals Study on the flexure performance of fine concrete sheets reinforced with textile and short fiber composites

2019 ◽  
Vol 275 ◽  
pp. 02006
Author(s):  
Qiao-chu Yang ◽  
Qin Zhang ◽  
Su-su Gong ◽  
San-ya Li
Keyword(s):  
Glass Fiber ◽  
Fiber Composite ◽  
Basalt Fiber ◽  
Fiber Composites ◽  
Short Fiber ◽  
Calcium Carbonate Whisker ◽  
Flexural Tests ◽  
Short Fiber Composite ◽  
Fiber Mesh ◽  
Concrete Matrix

In order to study the influences of the contents of short fiber on the mechanical properties of concrete matrix, the properties of compressive, flexure and splitting of concrete matrix reinforced by alkali resistant glass fiber and calcium carbonate whisker were tested. To study the reinforced effect of different scale fibers on the flexure behavior of fine concrete sheets, the flexural tests of concrete sheet of fine concrete reinforced with basalt fiber mesh and short fiber composites were carried out. The results show that the properties of the compressive, flexure and splitting of fine concrete reinforced with appropriate amount of alkali resistant glass fiber and carbonate whisker are improved compared with that of concrete reinforced by one type of fiber. The flexure properties of the concrete sheets are improved obviously when continuous fiber textile and short fiber composite are adopted to reinforce.

A Mechanistic Approach to Matrix Cracking Coupled with Fiber–Matrix Debonding in Short-Fiber Composites

2005 ◽  
Vol 127 (3) ◽  
pp. 337-350 ◽  
Author(s):  
Ba Nghiep Nguyen ◽  
Brian J. Tucker ◽  
Mohammad A. Khaleel
Keyword(s):  
Damage Mechanics ◽  
Fiber Composite ◽  
Fiber Composites ◽  
Short Fiber ◽  
Matrix Cracking ◽  
Element Analysis ◽  
Pull Out ◽  
Stiffness Reduction ◽  
Mechanistic Approach ◽  
Fiber Matrix

A micro–macro mechanistic approach to damage in short-fiber composites is developed in this paper. At the microscale, a reference aligned fiber composite is considered for the analysis of the damage mechanisms such as matrix cracking and fiber–matrix debonding using the modified Mori–Tanaka model. The associated damage variables are defined, and the stiffness reduction law dependent on these variables is established. The stiffness of a random fiber composite containing random matrix microcracks and imperfect interfaces is then obtained from that of the reference composite, which is averaged over all possible orientations and weighted by an orientation distribution function. The macroscopic response is determined using a continuum damage mechanics approach and finite element analysis. Final failure resulting from saturation of matrix microcracks, fiber pull-out and breakage is modeled by a vanishing element technique. The model is validated using the experimental results found in literature as well as the results obtained for a random chopped fiber glass–vinyl ester system. Acoustic emission techniques were used to quantify the amount and type of damage during quasi-static testing.

A Study on the Thermoelastic Analysis in Shear Deformable Discontinuous Composites

2004 ◽  
Vol 261-263 ◽  
pp. 645-650
Author(s):  
Hong Gun Kim
Keyword(s):  
Thermal Stresses ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Fiber Composite ◽  
Element Model ◽  
Short Fiber ◽  
Elastic Stresses ◽  
Fiber Aspect Ratio ◽  
The Matrix ◽  
Lag Model

A stress analysis has been performed to evaluate the thermally induced elastic stresses which can develop in a short fiber composite due to coefficient of thermal expansion (CTE) mismatch. An axisymmetric finite element model with the constraint between cells has implemented to find the magnitude of thermoelastic stresses in the fiber and the matrix as a function of volume fraction, CTE ratio, modulus ratio, and fiber aspect ratio. It was found that the matrix end regions fall under significant thermal stresses that have the same sign as that of the fibers themselves. Furthermore, it was found that the stresses vary along the fiber and fiber end gap in the same manner as that obtained in a shear-lag model during non-thermal mechanical loading.

Analysis of Mixed Mode Cracks in Two-Dimensional Magnetoelectroelastic Media

2006 ◽  
Vol 324-325 ◽  
pp. 403-406 ◽  
Author(s):  
Han Wang ◽  
Xian Hui Ke ◽  
Ming Hao Zhao
Keyword(s):  
Strain Energy Density ◽  
Mixed Mode ◽  
Strain Energy ◽  
The Self ◽  
Two Dimensional ◽  
Elliptical Cavity ◽  
Self Consistent ◽  
The Matrix ◽  
Consistent Method ◽  
Magnetoelectroelastic Medium

Based on the analytical solution for an elliptical cavity and the self-consistent method, the exact solutions for a crack in a two-dimensional magnetoelectroelastic medium is derived. The strain energy density factors are calculated for mixed mode cracks in a composite made of BaTiO3 as the inclusion and CoFe2O4 as the matrix.

Tensile Creep Damage and Rupture of Al2O3-SiO2(sf)/AZ91 Composite

2011 ◽  
Vol 55-57 ◽  
pp. 257-261
Author(s):  
Jun Tian ◽  
Shou Yan Zhong
Keyword(s):  
Creep Resistance ◽  
Load Transfer ◽  
Fiber Composite ◽  
Fiber Quality ◽  
Matrix Alloy ◽  
Short Fiber ◽  
Grain Boundary Sliding ◽  
Tensile Creep ◽  
Aluminum Silicate ◽  
The Matrix

Constant stress tensile creep tests were conducted on an AZ 91–25 vol.% Al2O3-SiO2short fiber composite and on an unreinforced AZ 91 matrix alloy. The creep resistance of the reinforced material is shown to be considerably improved compared with the matrix alloy. The creep strengthening arises mainly from the effective load transfer between plastic flow in the matrix and the fibers. Microstructural investigations by SEM revealed good fiber–matrix interface bonding during creep exposure. Short fibers have a great function in load bearing and load transfer, and greatly hinder the dislocation movement, thus enhancing the creep resistance of the composite. Damage and multiple rupture of aluminum silicate short fiber, quality of the interface combination between aluminum silicate short fiber reinforcement and the matrix, are two important factors of the creep deformation microstructure process control of Al2O3-SiO2(sf)/AZ91 composite. The creep mechanism of the composite is dislocation and grain boundary sliding control.

Continuous Carbon Nanotube-PDMS Composites

2008 ◽  
Author(s):  
Jonghwan Suhr ◽  
Lijie Ci ◽  
Jae-Soon Jang ◽  
Victor Pushparaj ◽  
Pulickel M. Ajayan
Keyword(s):  
Matrix Material ◽  
Fiber Composites ◽  
Short Fiber ◽  
Vertical Arrays ◽  
The Matrix ◽  
Nanotube Composites ◽  
Fiber Reinforcements ◽  
Longitudinal Modulus ◽  
Nanotube Growth ◽  
Damping Capability

Carbon nanotubes are considered short fibers and the nanotube reinforced composites are always analogues of randomly distributed short fiber composites. In contrast, the real structural fibrous composites often contain fiber reinforcements where fibers run continuously through the matrix material. With the recent advance in nanotube growth, vertical arrays of nanotubes in macroscopic lengths have become available and this allows the fabrication of continuous nano-composites that are similar to the continuous fiber composites utilizing the nanotube arrays as the continuous reinforcement in the composites. This provides a chance to take full advantage of the extreme high modulus and strength for the nanotubes in structural composites. Here, this study fabricates continuous nanotube reinforced polydimethylsiloxane (PDMS) composites and shows that under compressive loadings such continuous nanotube composites can generate dramatic increase in the longitudinal modulus and also significantly enhanced damping capability.

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