Effect of Fiber Aspect Ratio on Ultimate Properties of Short-Fiber Composites

1983 ◽  
pp. 407-423 ◽  
Author(s):  
J. L. Kardos ◽  
E. Masoumy ◽  
L. Kacir
Keyword(s):  
Aspect Ratio ◽  
Fiber Composites ◽  
Short Fiber ◽  
Fiber Aspect Ratio ◽  
Ultimate Properties

Mechanical Properties of Electrospun Carbon Nano Fiber (ECNF)/Epoxy Nanocomposites

2007 ◽  
Author(s):  
Darunee Aussawasathien ◽  
Erol Sancaktar
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Epoxy Resin ◽  
Carbon Nanofiber ◽  
Mechanical Analysis ◽  
Short Fiber ◽  
Neat Epoxy ◽  
Epoxy Nanocomposites ◽  
Cure Reaction ◽  
Fiber Aspect Ratio

Electrospun polyacrylonitrile (PAN) fiber precursor based Carbon Nanofiber (CNF) mats were produced and impregnated with epoxy resin. The mechanical properties of as-prepared nanofibers in the mat and short fiber filled epoxy nanocomposite forms were determined to demonstrate the effect of fiber aspect ratio and interconnecting network on those properties. Our experimental results reveal that epoxy nanocomposites containing Electrospun Carbon Nano Fibers (ECNF) with high fiber aspect ratio and high interconnecting network in the non-woven mat form yield better mechanical properties than those filled with short ECNFs. The ECNF mat in epoxy nanocomposites provides better homogeneity, more interlocking network, and easier preparation than short ECNFs. Mechanical properties of ECNF mat-epoxy nanocomposites, which we obtained using tensile and flexural tests, such as stiffness and modulus increased, while toughness and flexural strength decreased, compared to the neat epoxy resin. Dynamic Mechanical Analysis (DMA) results showed, higher modulus for ECNF mat-epoxy nanocomposites, compared to those for neat epoxy resin and short ECNF-epoxy nanocomposites. The epoxy nanocomposites had high modulus, even though the glass transition temperature, Tg values dropped at some extents of ECNF mat contents when compared with the neat epoxy resin. The cure reaction was retarded since the amount of epoxy and hardener decreased at high ECNF contents together with the hindering effect of the ECNF mat to the diffusion of epoxy resin and curing agent, leading to low crosslinking efficiency.

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.

Influence of Fiber Orientation and Aspect Ratio on the Effective Conductivity of Parallelepipedonal-Cell Short-Fiber Composites

2010 ◽  
Author(s):  
Juliana S. Bezerra ◽  
Manuel E. Cruz ◽  
Carlos F. Matt
Keyword(s):  
Composite Material ◽  
Heat Conduction ◽  
Aspect Ratio ◽  
Effective Conductivity ◽  
Fiber Composites ◽  
Short Fiber ◽  
Homogenization Theory ◽  
Interfacial Thermal Resistance ◽  
Periodic Composite ◽  
Variational Form

Modern applications of short-fiber composite materials demand accurate characterization of their macroscopic thermal properties. Many physical and microstructural factors influence the effective thermal conductivity of a composite material body. The objective of the current work is to investigate the influence of the microstructure configuration on the effective conductivity of a parallelepipedonal-cell composite containing equal-sized short fibers; the orientation and aspect ratio of the fibers are varied. The possible presence of voids in the matrix or of an interfacial thermal resistance between the constituent phases are not considered. A previous continuous formulation and computational implementation of heat conduction in a statistically homogeneous and periodic composite material are employed. The approach is based on the application of homogenization theory to the variational form of the original heat conduction boundary value problem for the multiscale composite medium. The variational form is well suited for subsequent numerical solution by the finite element method. The expression for the composite effective conductivity is here computed for several parallelepipedonal-cell microstructures. The numerical results are critically compared with available experimental data for short-fiber composites, and indications for important future research efforts are drawn.

Stress Field in and Around a Coated Short Fiber in an Infinite Matrix Subjected to Uniaxial and Biaxial Loadings

1985 ◽  
Vol 52 (1) ◽  
pp. 19-24 ◽  
Author(s):  
Y. Mikata ◽  
M. Taya
Keyword(s):  
Aspect Ratio ◽  
Stress Field ◽  
Fiber Composite ◽  
Short Fiber ◽  
Infinite Matrix ◽  
Matrix Stiffness ◽  
Stiffness Ratio ◽  
Infinite Body ◽  
Fiber Aspect Ratio ◽  
Short Fiber Composite

The stresses induced in and around a coated short-fiber composite are investigated by use of the Boussinesq-Sadowsky stress function. The coated fiber is assumed to consist of two confocal spheroids and it is embedded in an infinite body. The major parameters in this analysis are the fiber aspect ratio, the coating thickness-to-fiber radius ratio, the coating-to-matrix stiffness ratio and the fiber-to-matrix stiffness ratio. It is found in the analysis that the stiffness and thickness of the coating and the fiber aspect ratio have some effect on the stress field in and around the coating in a coated short-fiber composite.

Damping Properties of Vapor-Grown Carbon Fiber Composites

2000 ◽  
Author(s):  
Ioana C. Finegan ◽  
Gary G. Tibbetts ◽  
Ronald F. Gibson
Keyword(s):  
Carbon Fiber ◽  
Dynamic Properties ◽  
Fiber Composites ◽  
Dynamic Mechanical Properties ◽  
Short Fiber ◽  
Thermoplastic Composites ◽  
Carbon Fiber Composites ◽  
Fiber Aspect Ratio ◽  
Aspect Ratios ◽  
Injection Molded

Abstract The objective of this paper is to investigate analytically and experimentally the dynamic mechanical properties of vapor grown carbon fiber (VGCF)/thermoplastic composites. The experimental results show that, as predicted, very low fiber aspect ratios may produce significant improvements in damping. Since VGCF have submicron diameters and lengths, with a fiber aspect ratio, l/d = 19, good dynamic properties are obtained by using them as reinforcement in a thermoplastic. Fiber length distributions and orientation in the injection molded samples are determined by scanning electron microscopy (SEM). An analytical model based on the elastic-viscoelastic correspondence principle is developed to predict elastic properties in short fiber composites having a preferential fiber orientation in the direction of injection. The mechanical damping and storage modulus are analyzed experimentally by using a Dynamic Mechanic Analyzer (DMA).

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