Effective Mechanical Properties of Carbon-Carbon Composites

2014 ◽  
Author(s):  
Aswathi Sudhir ◽  
Abhilash M. Nagaraja ◽  
Suhasini Gururaja
Keyword(s):  
Mechanical Properties ◽  
Effective Properties ◽  
Leading Edge ◽  
Carbon Composites ◽  
Length Scales ◽  
Heterogeneous Microstructure ◽  
Specific Strength ◽  
C Fibers ◽  
Exit Nozzle ◽  
Effective Mechanical Properties

In recent times, composite materials have gained mainstream acceptance as a structural material of choice due to their tailorability and improved thermal, specific strength/stiffness and durability performance [1–3]. For high temperature applications, which include exit nozzle for rockets, leading edge for missiles, nose cones, brake pads etc. Carbon-Carbon composites (C/C composite) are found suitable [4–6]. Mechanical property estimation of C/C composites is challenging due to their highly heterogeneous microstructure. The highly heterogeneous microstructure consists of woven C-fibers, C-matrix, irregularly shaped voids, cracks and other inclusions. Predicting the mechanical behavior of complex hierarchical materials like C/C composites is of interest which forms the motivation for the present work. A systematic study to predict the effective mechanical properties of C/C composite using numerical homogenization has been undertaken in this work. The Micro-Meso-Macro (MMM) principle of ensemble averages for estimating the effective properties of the composite has been adopted. The hierarchical length scales in C/C composites were identified as micro (single fiber with matrix), meso (fabric) and macro (laminate). Comparisons have been made with mechanical testing of C/C composites at different length scales.

scholarly journals Numerical Estimation of Effective Mechanical Properties for Reinforced Plexiglas in the Two-Dimensional Case

2016 ◽  
Vol 2016 ◽  
pp. 1-10
Author(s):  
Vladimir Levin ◽  
Ignatiy Vdovichenko ◽  
Anatoly Vershinin ◽  
Maksim Yakovlev ◽  
Konstantin Zingerman
Keyword(s):  
Mechanical Properties ◽  
Cross Section ◽  
Effective Properties ◽  
Strain Tensor ◽  
Finite Strains ◽  
Dimensional Case ◽  
Two Dimensional ◽  
Numerical Estimation ◽  
Wire Cross Section ◽  
Effective Mechanical Properties

The paper describes an algorithm for numerical estimation of effective mechanical properties in two-dimensional case, considering finite strains. The algorithm is based on consecutive application of different boundary conditions to representative surface elements (RSEs) in terms of displacements, solution of elastic boundary value problem for each case, and averaging the stress field obtained. Effective properties are estimated as a quadratic dependence of the second Piola-Kirchhoff stress tensor upon the Green strain tensor. The results of numerical estimation of effective mechanical properties of plexiglas, reinforced with steel wire, are presented at finite strains. Numerical calculations were performed with the help of CAE Fidesys using the finite element method. The dependence of the effective properties of reinforced plexiglas upon the concentration of wires and the shape of wire cross section is investigated. In particular, it was found that the aspect ratio of reinforcing wire cross section has the most significant impact on effective moduli characterizing the material properties in the direction of larger side of the cross section. The obtained results allow one to estimate the influence of nonlinear effects upon the mechanical properties of the composite.

scholarly journals Evolutionary optimization of material properties of a tropical seed

2011 ◽  
Vol 9 (66) ◽  
pp. 34-42 ◽  
Author(s):  
Peter W. Lucas ◽  
John T. Gaskins ◽  
Timothy K. Lowrey ◽  
Mark E. Harrison ◽  
Helen C. Morrogh-Bernard ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Material Properties ◽  
Turgor Pressure ◽  
Selection Pressures ◽  
Damage Mechanisms ◽  
Length Scales ◽  
Damage Resistance ◽  
Heterogeneous Microstructure ◽  
Upper Limit

Here, we show how the mechanical properties of a thick-shelled tropical seed are adapted to permit them to germinate while preventing their predation. The seed has evolved a complex heterogeneous microstructure resulting in hardness, stiffness and fracture toughness values that place the structure at the intersection of these competing selective constraints. Analyses of different damage mechanisms inflicted by beetles, squirrels and orangutans illustrate that cellular shapes and orientations ensure damage resistance to predation forces imposed across a broad range of length scales. This resistance is shown to be around the upper limit that allows cracking the shell via internal turgor pressure (i.e. germination). Thus, the seed appears to strike an exquisitely delicate adaptive balance between multiple selection pressures.

On the Effective Mechanical Properties of Fluid-Saturated Composites: A Homogenization Approach

2010 ◽  
Vol 654-656 ◽  
pp. 2273-2276
Author(s):  
Lian Hua Ma ◽  
Bernard F. Rolfe ◽  
Qing Sheng Yang ◽  
Chun Hui Yang
Keyword(s):  
Mechanical Properties ◽  
Effective Properties ◽  
Micromechanical Model ◽  
Fluid Pressure ◽  
Fluid Phase ◽  
Homogenization Theory ◽  
Small Scale ◽  
Multi Scale ◽  
Homogenization Approach ◽  
Effective Mechanical Properties

Composites containing saturated fluid are widely distributed in nature, such as saturated rocks, colloidal materials and biological cells. In the study to determine effective mechanical properties of fluid-saturated composites, a micromechanical model and a multi-scale homogenization-based model are developed. In the micromechanical model the internal fluid pressure is generated by applying eigenstrains in the domain of the fluid phase and the explicit expressions of effective bulk modulus and shear modulus are obtained. Meanwhile a multi-scale homogenization theory is employed to develop the homogenization-based model on determination of effective properties at the small scale in a unit cell level. Applying the two proposed approaches, the effects of the internal pressure of hydrostatic fluid on effective properties are further investigated.

Influence of heterogeneities with different length scale on the plasticity of Fe-base ultrafine eutectic alloys

2008 ◽  
Vol 23 (7) ◽  
pp. 2003-2008 ◽  
Author(s):  
Jin Man Park ◽  
Do Hyang Kim ◽  
Ki Buem Kim ◽  
Min Ha Lee ◽  
Won Tae Kim ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Shear Bands ◽  
High Strength ◽  
Length Scale ◽  
Eutectic Alloys ◽  
Length Scales ◽  
Heterogeneous Microstructure ◽  
Evolution Of Microstructure ◽  
Co Alloys

The evolution of microstructure and its influence on the mechanical properties of high-strength ultrafine eutectic Fe–(Ti, Zr)–(B, Co) alloys has been studied. The addition of B or Co improves the room temperature compressive plasticity from 1% to ∼8.5% or ∼14%, respectively, due to the formation of a heterogeneous microstructure with distinctly different length scales, which can delay the propagation of shear bands and promotes the activation of multiple shear bands.

EVALUATION OF EFFECTIVE MECHANICAL PROPERTIES OF NANOCOMPOSITES REINFORCED WITH SINUSOIDAL CARBON NANOTUBES

NANO ◽  
2012 ◽  
Vol 07 (05) ◽  
pp. 1250041 ◽  
Author(s):  
HOSSEIN GOLESTANIAN ◽  
MAHDIEH HAMEDI
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Effective Properties ◽  
Theory Of Elasticity ◽  
Interface Strength ◽  
Reinforced Polymers ◽  
Reinforced Polymer ◽  
Elastic Interface ◽  
Longitudinal Modulus ◽  
Effective Mechanical Properties

Carbon nanotubes (CNTs) possess exceptional mechanical properties and are therefore suitable candidates for use as reinforcements in composite materials. Substantial improvements in mechanical properties of polymers have been attained through the addition of small amounts of CNTs. The CNTs, however, form complicated shapes and do not usually appear as straight reinforcements when introduced in polymer matrices. In this paper, theory of elasticity of anisotropic materials and finite element method (FEM) are used to determine effective mechanical properties of sinusoidal-nanotube reinforced polymers. The effects of CNT shape, orientation, and CNT distribution on nanocomposite effective properties are investigated by modeling different CNT-reinforced polymers. Also, the effects of interface strength on nanocomposite properties are investigated using an elastic interface model. The results indicate that even a slight nanotube curvature significantly reduces the reinforcing efficiency of sinusoidal — nanotubes compared to straight nanotubes. Also, in-plane isotropy was observed in the results obtained from the random CNT reinforced polymer. Finally, increasing the interface strength results in higher nanocomposite longitudinal modulus.

scholarly journals Homogenization of Heterogeneous Tissue Scaffold: A Comparison of Mechanics, Asymptotic Homogenization, and Finite Element Approach

2005 ◽  
Vol 2 (1) ◽  
pp. 17-29 ◽  
Author(s):  
Z. Fang ◽  
C. Yan ◽  
W. Sun ◽  
A. Shokoufandeh ◽  
W. Regli
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Finite Element ◽  
Effective Properties ◽  
Tissue Scaffolds ◽  
Homogenization Theory ◽  
Tissue Scaffold ◽  
Finite Element Approach ◽  
Element Approach ◽  
Effective Mechanical Properties

Actual prediction of the effective mechanical properties of tissue scaffolds is very important for tissue engineering applications. Currently common homogenization methods are based on three available approaches: standard mechanics modeling, homogenization theory, and finite element methods. Each of these methods has advantages and limitations. This paper presents comparisons and applications of these approaches for the prediction of the effective properties of a tissue scaffold. Derivations and formulations of mechanics, homogenization, and finite element approach as they relate to tissue engineering are described. The process for the development of a computational algorithm, finite element implementation, and numerical solution for calculating the effective mechanical properties of porous tissue scaffolds are also given. A comparison of the results based upon these different approaches is presented. Parametric analyses using the homogenization approach to study the effects of different scaffold materials and pore shapes on the properties of the scaffold are conducted, and the results of the analyses are also presented.

An Analytical Thermodynamic Approach to Friction of Rubber on Ice

2012 ◽  
Vol 40 (2) ◽  
pp. 124-150
Author(s):  
Klaus Wiese ◽  
Thiemo M. Kessel ◽  
Reinhard Mundl ◽  
Burkhard Wies
Keyword(s):  
Coefficient Of Friction ◽  
Liquid Layer ◽  
Contact Area ◽  
Leading Edge ◽  
Viscous Friction ◽  
Analytical Approximation ◽  
Real Contact Area ◽  
Length Scales ◽  
Real Contact ◽  
Ice Surface

ABSTRACT The presented investigation is motivated by the need for performance improvement in winter tires, based on the idea of innovative “functional” surfaces. Current tread design features focus on macroscopic length scales. The potential of microscopic surface effects for friction on wintery roads has not been considered extensively yet. We limit our considerations to length scales for which rubber is rough, in contrast to a perfectly smooth ice surface. Therefore we assume that the only source of frictional forces is the viscosity of a sheared intermediate thin liquid layer of melted ice. Rubber hysteresis and adhesion effects are considered to be negligible. The height of the liquid layer is driven by an equilibrium between the heat built up by viscous friction, energy consumption for phase transition between ice and water, and heat flow into the cold underlying ice. In addition, the microscopic “squeeze-out” phenomena of melted water resulting from rubber asperities are also taken into consideration. The size and microscopic real contact area of these asperities are derived from roughness parameters of the free rubber surface using Greenwood-Williamson contact theory and compared with the measured real contact area. The derived one-dimensional differential equation for the height of an averaged liquid layer is solved for stationary sliding by a piecewise analytical approximation. The frictional shear forces are deduced and integrated over the whole macroscopic contact area to result in a global coefficient of friction. The boundary condition at the leading edge of the contact area is prescribed by the height of a “quasi-liquid layer,” which already exists on the “free” ice surface. It turns out that this approach meets the measured coefficient of friction in the laboratory. More precisely, the calculated dependencies of the friction coefficient on ice temperature, sliding speed, and contact pressure are confirmed by measurements of a simple rubber block sample on artificial ice in the laboratory.

scholarly journals Biological Applications of Severely Plastically Deformed Nano-Grained Medical Devices: A Review

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 748
Author(s):  
Katayoon Kalantari ◽  
Bahram Saleh ◽  
Thomas J. Webster
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Bacterial Colonization ◽  
Antibiotic Use ◽  
Bone Cell ◽  
Corrosion Properties ◽  
Biomedical Implant ◽  
Specific Strength ◽  
Biological Functionality ◽  
Bone Cell Proliferation

Metallic materials are widely used for fabricating medical implants due to their high specific strength, biocompatibility, good corrosion properties, and fatigue resistance. Recently, titanium (Ti) and its alloys, as well as stainless steel (SS), have attracted attention from researchers because of their biocompatibility properties within the human body; however, improvements in mechanical properties while keeping other beneficial properties unchanged are still required. Severe plastic deformation (SPD) is a unique process for fabricating an ultra-fine-grained (UFG) metal with micrometer- to nanometer-level grain structures. SPD methods can substantially refine grain size and represent a promising strategy for improving biological functionality and mechanical properties. This present review paper provides an overview of different SPD techniques developed to create nano-/ultra-fine-grain-structured Ti and stainless steel for improved biomedical implant applications. Furthermore, studies will be covered that have used SPD techniques to improve bone cell proliferation and function while decreasing bacterial colonization when cultured on such nano-grained metals (without resorting to antibiotic use).

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