Mechanics of Fatigue Damage and Degradation in Random Short-Fiber Composites, Part II—Analysis of Anisotropic Property Degradation

1986 ◽  
Vol 53 (2) ◽  
pp. 347-353 ◽  
Author(s):  
S. S. Wang ◽  
E. S.-M. Chim ◽  
H. Suemasu
Keyword(s):  
Fatigue Damage ◽  
Fiber Composite ◽  
Fiber Composites ◽  
Short Fiber ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Stiffness Degradation ◽  
Microcrack Density ◽  
Loading Cycle ◽  
Anisotropic Stiffness

Based on the microcrack density and cumulative distribution functions obtained in (Wang et al., 1986), cyclic fatigue degradation and associated damage-induced anisotropy of elastic properties of random short-fiber composites are studied. Constitutive equations of the fatigue-damaged composite are derived on the basis of the well-known self-consistent mechanics scheme in conjunction with a three-dimensional elliptic crack theory and the probabilistic functions of microcrack density and cumulative distribution. The anisotropic stiffness degradation is determined as a function of microcrack evolution and accumulation in the damaged composite. Theoretical predictions and experimental data of effective modulus decay during fatigue are in excellent agreement. A damage parameter is introduced to depict quantitatively the degree of homogeneous fatigue damage. The tensorial nature of anisotropic stiffness degradation and fatigue damage is examined in detail. A power-law relationship is established between the rate of damage development and the fatigue loading cycle. The rate of fatigue damage growth is found to decrease exponentially with the loading cycle — a phenomenon unique to the random short-fiber composite. The fundamental mechanics of composite fatigue damage and associated property degradation is elucidated in this paper.

Mechanics of Fatigue Damage and Degradation in Random Short-Fiber Composites, Part I—Damage Evolution and Accumulation

1986 ◽  
Vol 53 (2) ◽  
pp. 339-346 ◽  
Author(s):  
S. S. Wang ◽  
E. S.-M. Chim ◽  
H. Suemasu
Keyword(s):  
Fatigue Damage ◽  
Damage Evolution ◽  
Fiber Composite ◽  
Cyclic Fatigue ◽  
Fiber Composites ◽  
Short Fiber ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Orientation Density ◽  
Short Fiber Composite

Cyclic fatigue damage in random short-fiber composites is studied experimentally and analytically. In the experimental phase of the study, the fatigue damage is observed to involve various forms of microcracking, originated from microscopic stress concentrators in the highly heterogeneous microstructure. In the analytical portion of the study, a probabilistic treatment of the microcracks is conducted to evaluate the statistical nature of the microscopic fatigue damage. The density and the cumulative distribution of microcrack lengths are found to follow the well known Weibull-form function, and the microcrack orientation density and cumulative distribution have expressions of a fourth-order power form of the cosθ function. Fatigue damage evolution and accumulation in the random short-fiber composite are analyzed in detail through the development of probabilistic microcrack density and distribution functions during the cyclic loading history.

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.

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.

scholarly journals Maximum Entropy Models for Fatigue Damage in Metals with Application to Low-Cycle Fatigue of Aluminum 2024-T351

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 967 ◽  
Author(s):  
Young ◽  
Subbarayan
Keyword(s):  
Maximum Entropy ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Hysteresis Loops ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Cycle Fatigue ◽  
Damage Models ◽  
Cumulative Distribution Functions ◽  
Thermodynamic Entropy

In the present work, we propose using the cumulative distribution functions derived from maximum entropy formalisms, utilizing thermodynamic entropy as a measure of damage to fit the low-cycle fatigue data of metals. The thermodynamic entropy is measured from hysteresis loops of cyclic tension–compression fatigue tests on aluminum 2024-T351. The plastic dissipation per cyclic reversal is estimated from Ramberg–Osgood constitutive model fits to the hysteresis loops and correlated to experimentally measured average damage per reversal. The developed damage models are shown to more accurately and consistently describe fatigue life than several alternative damage models, including the Weibull distribution function and the Coffin–Manson relation. The formalism is founded on treating the failure process as a consequence of the increase in the entropy of the material due to plastic deformation. This argument leads to using inelastic dissipation as the independent variable for predicting low-cycle fatigue damage, rather than the more commonly used plastic strain. The entropy of the microstructural state of the material is modeled by statistical cumulative distribution functions, following examples in recent literature. We demonstrate the utility of a broader class of maximum entropy statistical distributions, including the truncated exponential and the truncated normal distribution. Not only are these functions demonstrated to have the necessary qualitative features to model damage, but they are also shown to capture the random nature of damage processes with greater fidelity.

scholarly journals Fabrication, Modeling and Characterization of Magnetostrictive Short Fiber Composites

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1494 ◽  
Author(s):  
Zhenjin Wang ◽  
Kotaro Mori ◽  
Kenya Nakajima ◽  
Fumio Narita
Keyword(s):  
Present Model ◽  
Epoxy Composite ◽  
Fiber Composite ◽  
Fiber Composites ◽  
Short Fiber ◽  
Composite Sheet ◽  
Epoxy Matrix Composite ◽  
Energy Harvesting Devices ◽  
Magnetostrictive Devices

Magnetostrictive materials have a wide variety of applications due to their great capability as sensors and energy-harvesting devices. However, their brittleness inhibits their applications as magnetostrictive devices. Recently, we developed a continuous magnetostrictive Fe-Co-fiber-embedded epoxy matrix composite to increase the flexibility of the material. In this study, we fabricated random magnetostrictive Fe-Co short fiber/epoxy composite sheets. It was found that the discontinuous Fe-Co fiber composite sheet has the magnetostrictive properties along the orientation parallel to the length of the sheet. Finite element computations were also carried out using a coupled magneto-mechanical model, for the representative volume element (RVE) of unidirectional aligned magnetostrictive short fiber composites. A simple model of two-dimensional, randomly oriented, magnetostrictive short fiber composites was then proposed and the effective piezomagnetic coefficient was determined. It was shown that the present model is very accurate yet relatively simple to predict the piezomagnetic coefficient of magnetostrictive short fiber composites. This magnetostrictive composite sheet is expected to be used as a flexible smart material.

Effective Thermal Conductivity of Ordered Short-Fiber Composites With Single-Fiber Uniform Hexagonal Prism Cell

2012 ◽  
Author(s):  
Marcelo B. Martinez ◽  
Manuel E. Cruz ◽  
Carlos F. Matt
Keyword(s):  
Finite Element ◽  
Effective Properties ◽  
Effective Conductivity ◽  
Numerical Study ◽  
Fiber Composite ◽  
Fiber Composites ◽  
Short Fiber ◽  
Single Fiber ◽  
Hexagonal Prism ◽  
Element Discretization

The bulk behavior of short-fiber composite materials in mechanical, thermal, and electrical applications is of great engineering interest. The reliability of analytical and numerical studies dedicated to these topics depends to a large extent on the postulated, or prescribed, microstructure configurations. Of course, different spatial distributions of fibers lead to different configurations, which in turn influence the effective properties. There are no established (or benchmarked) microstructure configurations (or models) to be used in investigations aimed at calculating the macroscopic behavior of classes of real composite material bodies. In the present numerical study of heat conduction in composites, accurate results for the longitudinal and transverse effective thermal conductivities of short-fiber composites with single-fiber uniform hexagonal prism cell are calculated and validated. The three-dimensional periodic cell microstructure consists of one short circular cylindrical fiber placed at the center, and perpendicular to the two parallel regular hexagons, of the prism. Previous continuous formulation and computational implementation are employed, based on the method of homogenization and finite element discretization. A procedure for generating the domain of the uniform hexagonal prism cell, and the respective tetrahedral finite-element mesh, has been realized using a third-party software. The numerical effective conductivity results obtained in the 3-D calculations are validated against analytical results for the 2-D hexagonal array of circular cylinders.

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