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.

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.

Thermal Residual Stress in a Two-Dimensional In-Plane Misoriented Short Fiber Composite

1990 ◽  
Vol 43 (5S) ◽  
pp. S294-S303 ◽  
Author(s):  
M. Taya ◽  
M. Dunn ◽  
B. Derby ◽  
J. Walker
Keyword(s):  
Residual Stress ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Short Fiber ◽  
Two Dimensional ◽  
Fiber Distribution ◽  
Fiber Volume ◽  
Distribution Type ◽  
Short Fiber Composite

Residual stress induced in a misoriented short fiber composite due to thermal expansion mismatch between the matrix and fiber is investigated. The case of two-dimensional in-plane fiber misorientation is considered. The elastic model that is developed is based on Eshelby’s equivalent inclusion method and is unique in that it accounts for interactions among fibers at different orientations. A parametric study is performed to demonstrate the effects of fiber volume fraction, fiber aspect ratio, fiber distribution cut-off angle, and fiber distribution type on thermal residual stress. Fiber volume fraction and aspect ratio are shown to have more significant effects on the magnitude of the thermal residual stresses than the fiber distribution type and cut-off angle.

Effect of surface density and fiber length on the porosity and permeability of nonwoven flax reinforcement

2017 ◽  
Vol 88 (15) ◽  
pp. 1776-1787 ◽  
Author(s):  
Mohamed Habibi ◽  
Édu Ruiz ◽  
Gilbert Lebrun ◽  
Luc Laperrière
Keyword(s):  
Pore Size ◽  
Surface Density ◽  
Fiber Length ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Short Fiber ◽  
Fiber Volume ◽  
Fibrous Network ◽  
Porosity And Permeability ◽  
The Impact

This paper presents an experimental study and modeling of the influence of surface density and fiber length on the permeability of novel nonwoven flax fiber manufactured by the paper making process. Firstly, the relation between surface density, fiber lengths and pore size distribution measured with a porometer capillary instrument is reported in this study. The results show that higher surface density gives a denser fibrous network with a low porosity rate and longer fiber decreases the total number of fibers and increases the pore size for a given surface density. A liquid permeability study was then carried out to identify the impact of surface density, short fiber length and fiber volume fraction on in-plane impregnation of the reinforcement. Permeability was found to be inversely proportional to the reinforcement of surface density. In contrast, an increase of the fiber length increases the in-plane permeability of the reinforcement. Finally, a mathematical modeling is proposed to predict the permeability behavior of these innovative natural fiber webs.

scholarly journals Micro-scale numerical study of fiber/matrix debonding in steel fiber composites

2020 ◽  
Vol 15 ◽  
pp. 155892502091072 ◽  
Author(s):  
Baris Sabuncuoglu ◽  
Stepan V Lomov
Keyword(s):  
Steel Fiber ◽  
Volume Fraction ◽  
Numerical Study ◽  
Glass Fibers ◽  
Fiber Composites ◽  
Steel Fibers ◽  
Opening Angle ◽  
Stress Concentrations ◽  
Fiber Volume ◽  
Fiber Matrix

Fiber/matrix debonding behavior of steel fiber composites is analyzed using a parametric finite element modeling procedure and compared with conventional composites with carbon and glass fibers. Cohesive surfaces are applied to fiber–matrix interface to simulate the debonding behavior, while the interface strength properties of steel fiber are obtained with and without surface treatment. The effect of various parameters on the debonding behavior is investigated, including stress concentrations, fiber diameter, fiber shape, and fiber volume fraction, using the parametric model. The influence of stress concentrations is determined to be much lower than the debonding strength. Debonding damage is more evident in larger fibers compared to smaller ones. Earlier and sudden interface separation is observed with the polygonal steel fibers compared to the circular ones. Increase in the fiber volume ratio increases the debonding opening distance but does not affect the opening angle significantly. The results can be useful for assessing possibilities to use steel fibers to increase toughness of the composites in comparison with glass and carbon reinforcement.

Fracture behavior of short-fiber reinforced materials

1992 ◽  
Vol 7 (11) ◽  
pp. 3120-3131 ◽  
Author(s):  
Michael Murat ◽  
Micha Anholt ◽  
H. Daniel Wagner
Keyword(s):  
Fracture Process ◽  
Fracture Behavior ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Finite Size ◽  
Critical Length ◽  
Short Fiber ◽  
Fiber Volume ◽  
Linear Elastic ◽  
Fiber Reinforced Materials

A discrete model of springs with bond-bending forces is proposed to simulate the fracture process in a composite of short stiff fibers in a softer matrix. Both components are assumed to be linear elastic up to failure. We find that the critical fiber length of a single fiber composite increases roughly linearly with the ratio of the fiber elastic modulus to matrix modulus. The finite size of the lattice in the direction perpendicular to the fiber orientation considerably alters the behavior of the critical length for large values of the modulus ratio. The simulations of the fracture process reveal different fracture behavior as a function of the fiber content and length. We calculate the Young's modulus, fracture stress, and the strain at maximum stress as a function of the fiber volume fraction and aspect ratio. The results are compared with the predictions of other theoretical studies and experiments.

Fiber-Matrix Interfacial Area Reduction in Fiber Reinforced Cements and Concretes at Moderate to High Fiber Volume Fractions

1994 ◽  
Vol 370 ◽  
Author(s):  
Gebran N. Karam
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Interfacial Area ◽  
Composite Fiber ◽  
Short Fiber ◽  
Published Data ◽  
Fiber Reinforced ◽  
Fiber Volume ◽  
High Fiber ◽  
Fiber Matrix

AbstractThe area and properties of the fiber-matrix interface in fiber reinforced cements and concretes determines the amount of stress transferred forth and back between the cement paste and the reinforcement and hence controls the mechanical properties of the composite. Fiber-fiber interaction and overlap of fibers with fibers, voids and aggregates can dramatically decrease the efficiency of the reinforcement by reducing this interfacial area. A simple model to account for this reduction is proposed and ways to integrate it in the models describing the mechanical properties of short fiber reinforced concretes are presented. The parameters of the model are evaluated from previously published data sets and its predictions are found to compare well with experimental observations; for example, it is able to predict the non-linear variation of bending and tensile strength with increasing fiber volume fraction as well as the existence of an optimal fiber content.

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