Mechanical Evaluation of Hydroxyapatite Nanocomposites Using Finite Element Modeling

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Kristopher Doll ◽  
Ani Ural
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Elastic Modulus ◽  
Aspect Ratio ◽  
Finite Element Modeling ◽  
Graphene Nanosheets ◽  
Bone Implants ◽  
Graphene Nanosheet ◽  
Computational Framework ◽  
Element Modeling

Hydroxyapatite (HA) has been proposed as a candidate material for bone implants because of its similarity to the inorganic phase in bone. However, due to its lower mechanical properties compared to bone, it has not been used in load bearing bone implants. Inclusion of second phase reinforcements in HA such as carbon nanotubes (CNT) and graphene nanosheets is expected to significantly improve its mechanical properties. In this study, a computational framework that will improve the understanding of the mechanical behavior of graphene nanosheet and CNT-reinforced HA-nanocomposites is proposed. The variation of elastic modulus of HA-nanocomposites is assessed based on the nanofiller type, volume fraction, alignment, area, thickness, and aspect ratio using the finite element modeling. The results of the simulations show that graphene nanosheets are more effective in improving the elastic modulus of nanocomposites than CNTs at similar volume fractions. HA-nanocomposites reinforced by graphene nanosheets exhibit transversely isotropic material properties and provide the highest elastic modulus when aligned along a direction or randomly distributed in a plane, whereas CNTs provide the best reinforcement when aligned along an axis. Variation in graphene nanosheet area, thickness, aspect ratio, and carbon nanotube length have negligible effect on elastic modulus of the HA-nanocomposite. In addition, comparison between the finite element simulations and theoretical calculations show that clustering of nanoinclusions reduces the effectiveness of the reinforcement they provide. The simulation results and the computational framework presented in this study are expected to help in determining the best design and manufacturing parameters that can be adapted for developing HA-nanocomposite bone implant materials.

The Study of Wrinkling Mechanism of Plasma-Treated Microphase-Separated Polyurethane Surface

2018 ◽  
Vol 773 ◽  
pp. 3-9 ◽  
Author(s):  
Ilya A. Morozov ◽  
Anton Y. Beliaev ◽  
Roman I. Izyumov
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Elastic Modulus ◽  
Finite Element Modeling ◽  
Layer Surface ◽  
Element Modeling ◽  
Compression Deformation ◽  
Good Accordance ◽  
Nitrogen Ions ◽  
External Strain

Stiff coating on the phase-separated soft polyurethane substrate under the compression deformation is investigated by the finite element modeling (FEM). External strain leads to the wrinkling of layer surface, which is characterized by a set of wavelengths and amplitudes. The influence of the thickness and stiffness of the layer, elastic modulus of the substrate on the structural-mechanical properties of the deformed surface is studied. The results of the model are in good accordance with the experiment (plasma immersion ion impanation of nitrogen ions into the polyurethane substrate) and allowed to estimate the modulus of the coating and the deformation of the surface.

Finite Element Modeling of Bone Ultrastructure as a Two-phase Composite

2004 ◽  
Vol 844 ◽  
Author(s):  
Michelle L. Oyen ◽  
Ching-Chang Ko
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Aspect Ratio ◽  
Finite Element Modeling ◽  
Experimental Results ◽  
Mineral Phase ◽  
Two Phase ◽  
Element Modeling ◽  
Reinforcing Particles ◽  
Transverse Modulus

ABSTRACTBone is a composite material with a mineral hydroxyapatite (HA) phase and an organic collagen-based phase. Each phase represents about half the material by volume. The precise arrangement of these components at the ultrastructural level is unclear but of great interest in understanding the mechanical functionality of bone. Nanoindentation tests show that the elastic modulus of bone is primarily distributed between 10 GPa and 30 GPa. In this study we examine different ultrastructural arrangements of collagen and apatite phases, to test different proposed models for bone composite ultrastructure within the same finite element modeling framework. Different configurations of the composite are considered, including (a) a compliant phase with stiff reinforcing particles, (b) a stiff phase with compliant reinforcing particles, and (c) an interpenetrating two-phase (co-continuous) composite. An elastic modulus of 100 GPa is used for the mineral phase and 100 MPa for the organic phase, with volume fraction of each phase fixed at 0.5. Stiff phase continuity (as the only continuous phase in 2D and 3D or as one of two continuous phases in 3D) gives rise to effective composite elastic modulus values of 25–35 GPa, similar to the experimental results for bone modulus. Isotropic models with compliant phase continuity only give rise to moduli around 300 MPa, far below experimental results. Anisotropy was evaluated by calculating effective moduli in parallel and transverse directions relative to the primary axes of rectangular particles. High aspect ratio, stiff particles embedded in a compliant matrix do result in a substantially stiffened composite in the direction of the particles when compared to symmetric particles. However, this configuration results in a material with an effective elastic modulus of 2 GPa along the particle direction but a transverse modulus of only 250 MPa. Decreased interparticle spacing in the direction of loading was the mechanism for stiffening parallel to the particle long axis, demonstrating an indirect effect of particle aspect ratio. Although many bone models have considered the mineral as a particle reinforcement phase, the current results suggest this arrangement would not give rise to a material with bonelike properties, particularly when transverse modulus is considered, regardless of the particle geometry. Some degree of continuity of the mineral phase is required for bone-like elastic modulus values and thus a partially to fully co-continuous ultrastructural arrangement of phases is supported.

scholarly journals Hardening of Nickel Alloys by Ion Implantation of Titanium and Carbon

1996 ◽  
Vol 444 ◽  
Author(s):  
S. M. Myers ◽  
D. M. Follstaedt ◽  
J. A. Knapp ◽  
T. R. Christenson
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Surface Layer ◽  
Ion Implantation ◽  
Finite Element Modeling ◽  
Yield Stress ◽  
Nickel Alloys ◽  
Element Modeling ◽  
Order Of Magnitude ◽  
Amorphous Surface

AbstractDual ion implantation of titanium and carbon was shown to produce an amorphous surface layer in annealed bulk nickel, in electroformed Ni, and in electroformed Ni7 5Fe 2 5. Diamond-tip nanoindentation coupled with finite-element modeling quantified the elastic and plastic mechanical properties of the implanted region. The amorphized matrix, with a thickness of about 100 nm, has a yield stress of approximately 6 GP and an intrinsic hardness near 16 GPa, exceeding by an order of magnitude the corresponding values for annealed bulk Ni. Implications for micro-electromechanical systems are discussed.

scholarly journals Evaluating Mechanical Properties of Thin Layers using Nanoindentation and Finite-Element Modeling: Implanted Metals and Deposited Layers

1996 ◽  
Vol 438 ◽  
Author(s):  
J. A. Knapp ◽  
D. M. Follstaedt ◽  
J. C. Barbour ◽  
S. M. Myers ◽  
J. W. Ager ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Modeling ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Layer Thickness ◽  
Young's Modulus ◽  
Thin Layers ◽  
Element Modeling ◽  
Surface Modified

AbstractWe present a methodology based on finite-element modeling of nanoindentation data to extract reliable and accurate mechanical properties from thin, hard films and surface-modified layers on softer substrates. The method deduces the yield stress, Young's modulus, and hardness from indentations as deep as 50% of the layer thickness.

Finite Element Modeling of Grain Aspect Ratio and Strain Energy Density in a Textured Copper Thin Film

1996 ◽  
Vol 436 ◽  
Author(s):  
R. P. Vinci ◽  
J. C. Bravman
Keyword(s):  
Finite Element ◽  
Energy Density ◽  
Aspect Ratio ◽  
Finite Element Modeling ◽  
Strain Energy Density ◽  
Driving Force ◽  
Strain Energy ◽  
Interface Energy ◽  
Element Modeling ◽  
Grain Aspect Ratio

AbstractWe have modeled the effects of grain aspect ratio on strain energy density in (100)-oriented grains in a (111)-textured Cu film on a Si substrate. Minimization of surface energy, interface energy, and strain energy density (SED) drives preferential growth of grains of certain crystallographic orientations in thin films. Under conditions in which the SED driving force exceeds the surface- and interface-energy driving forces, Cu films develop abnormally large (100) oriented grains during annealing. In the elastic regime the SED differences between the (100) grains and the film average arise from elastic anisotropy. Previous analyses indicate that several factors (e.g. elimination of grain boundaries during grain growth) may alter the magnitude of the SED driving force. We demonstrate, using finite element modeling of a single columnar (100) grain in a (111) film, that changes in grain aspect ratio can significantly affect the SED driving force. A minimum SED driving force is found for (100) Cu grains with diameters on the order of the film thickness. In the absence of other stagnation mechanisms, such behavior could cause small grains to grow abnormally and then stagnate while large grains continue to grow. This would lead to a bimodal grain size distribution in the (100) grains preferred by the SED minimization.

Computing Thin Film Mechanical Properties With the Oliver and Pharr Method

1999 ◽  
Vol 593 ◽  
Author(s):  
P.J. Wolff ◽  
B.N. Lucas ◽  
E.G. Herbert
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Modeling ◽  
Dimensional Analysis ◽  
Film Properties ◽  
Element Modeling ◽  
Indentation Tests

ABSTRACTA commonly used technique to compute mechanical properties from indentation tests is the Oliver and Pharr method. Using dimensional analysis and finite element modeling, this paper investigates errors when the Oliver and Pharr method is used to compute thin film properties.

Sign in / Sign up

Export Citation Format

Share Document