Production and Digital Image Correlation Analysis of Titanium Foams with Different Pore Morphologies as a Bone-Substitute Material

Mohammed Shbeh,Russell Goodall,Elif Oner,Ammar Al-Rubaye

doi:10.1155/2019/1670837

Mohammed Shbeh, Russell Goodall + Show 2 more

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https://doi.org/10.1155/2019/1670837

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Abstract

Ti foams are mesoporous structured materials that are characterized by their high surface area and interconnected porosity with a huge potential for biomedical applications. In this study, we investigated the production of titanium foams with different pore morphologies as a bone-substitute material via the addition of different amounts, shapes, and sizes of the space holder. Furthermore, we also carried out strain analysis using digital image correlation (DIC) in order to analyse the strain distribution across the porous samples. In addition, the nature of the relationship between the amount of the space holder added and final amount of porosity in the foams produced was also examined. The results demonstrated that the relationship between the space holder amount and porosity in the samples follows a complex one-phase exponential decay function in an increasing form. Our findings also suggest that the shape of the space holder does not play a significant role in dictating the porosity of the foams produced in the current study. However, the space holder’s shape does have a substantial role in dictating the mechanical properties of the foams produced, where Ti foams produced using a cubic or irregular space holder were found to have a lower yield stresses than those made with the spherical space holder.

Highlights

Human bone is a complex composite material composed of organic and inorganic components. e organic part of the bone is comprised of a matrix polymer known as collagen, which is responsible for giving the bone its toughness, whereas the inorganic element of the bone has a similar chemical and crystal structure to that of a ceramic material, hydroxyapatite, and plays an important role in providing the bone with strength and stiffness [1, 2]
Increased amount of the binder can result in an increase in the volume shrinkage of samples. erefore, a balance between those two must be reached for reduced initial porosity and accepted volume shrinkage. Adding another material to the feedstock during mixing in addition to the Ti can make it more difficult for the binder to wet all of the particles without leaving voids, resulting in an increased amount of initial porosity, depending on the mixing procedure. us, it is important to investigate the effect of adding the space holder to the samples on the initial porosity and green strength in order to assess the ability of these samples to withstand mechanical handling before debinding, as well as to make sure that this initial porosity is maintained at an acceptable level
E results of the compression testing of the Ti foams made by different shapes and sizes of space holders are shown in Figure 11. e results demonstrated that Ti foams made by the spherical space holder have higher yield stresses than those made with the cubic space holder. is might be due to the shape of pores present in the samples, where cracks can initiate more in the samples with irregular and angular pores compared to regular spherical pores, as they act as stress concentration sites with preformed crack tips or sharp corners, and samples yield at a lower stress value

Summary

Introduction

Human bone is a complex composite material composed of organic and inorganic components. e organic part of the bone is comprised of a matrix polymer known as collagen, which is responsible for giving the bone its toughness, whereas the inorganic element of the bone has a similar chemical and crystal structure to that of a ceramic material, hydroxyapatite, and plays an important role in providing the bone with strength and stiffness [1, 2]. The cortical bone constitutes the outer tubular shell of the long bones and the external surface of the small and flat bones, while the trabecular bone composes the internal surface of small bones, the ends of the long bones, and between the surfaces of flat bones [6] In some cases, such as severe damage or osteoporotic fractures, bones need to be replaced. Successful replacement of such hard tissue with an anisotropic complex structure and mechanical properties can be challenging without the use of appropriate biocompatible and biomimetic materials.

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