Influence of porosity on compressive and tensile strength of cement mortar

http://nucapt.northwestern.edu/refbase/files/Bansiddhi-2008_10363.pdf

Porous NiTi for bone implants: a review.

Fabrication, properties and application of porous metals with directional pores

It is widely known that the availability of lightweight structures with excellent energy absorption capacity is essential for numerous engineering applications. Inspired by many biological structures in nature, bio-inspired structures have been proved to exhibit a significant improvement over conventional structures in energy absorption capacity. Therefore, use of the biomimetic approach for designing novel lightweight structures with excellent energy absorption capacity has been increasing in engineering fields in recent years. This paper provides a comprehensive overview of recent advances in the development of bio-inspired structures for energy absorption applications. In particular, we describe the unique features and remarkable mechanical properties of biological structures such as plants and animals, which can be mimicked to design efficient energy absorbers. Next, we review and discuss the structural designs as well as the energy absorption characteristics of current bio-inspired structures with different configurations and structures, including multi-cell tubes, frusta, sandwich panels, composite plates, honeycombs, foams, building structures and lattices. These materials have been used for bio-inspired structures, including but not limited to metals, polymers, fibre-reinforced composites, concrete and glass. We also discussed the manufacturing techniques of bio-inspired structures based on conventional methods, and adaptive manufacturing (3D printing). Finally, contemporary challenges and future directions for bio-inspired structures are presented. This synopsis provides a useful platform for researchers and engineers to create novel designs of bio-inspired structures for energy absorption applications.

A review of recent research on bio-inspired structures and materials for energy absorption applications

Bone tissue engineering is an emerging interdisciplinary field in Science, combining expertise in medicine, material science and biomechanics. Hard tissue engineering research is focused mainly in two areas, osteo and dental clinical applications. There is a lot of exciting research being performed worldwide in developing novel scaffolds for tissue engineering. Although, nowadays the majority of the research effort is in the development of scaffolds for non-load bearing applications, primarily using soft natural or synthetic polymers or natural scaffolds for soft tissue engineering; metallic scaffolds aimed for hard tissue engineering have been also the subject of in vitro and in vivo research and industrial development. In this article, descriptions of the different manufacturing technologies available to fabricate metallic scaffolds and a compilation of the reported biocompatibility of the currently developed metallic scaffolds have been performed. Finally, we highlight the positive aspects and the remaining problems that will drive future research in metallic constructs aimed for the reconstruction and repair of bone.

https://www.mdpi.com/1996-1944/2/3/790/pdf

Metallic Scaffolds for Bone Regeneration

Porous copper whose long cylindrical pores are aligned in one direction has been fabricated by unidirectional solidification of the melt in a mixture gas of hydrogen and argon. The porosity depends on the melting temperature of copper melt, while the orientation of the pores is controlled by the freezing direction. The anisotropy in the uniaxial tensile behavior of the porous copper is examined. The ultimate tensile strength and the yield strength of the porous copper with the cylindrical pores orientated parallel to the tensile direction decrease linearly with increasing the porosity. For the porous copper whose pore axes are perpendicular to the tensile direction, the ultimate tensile strength decreases significantly with increasing the porosity at low porosity, while the yield strength reaches a maximum at a low porosity and then decreases with increasing the porosity. These results are explained in terms of the stress concentration induced in the vicinity of the pores during tensile deformation.

Anisotropic mechanical properties of porous copper fabricated by unidirectional solidification

Porous copper whose long cylindrical pores are aligned in one direction has been fabricated by unidirectional solidification of the melt in a mixture gas of hydrogen and argon. The compressive yield strength of the porous copper with the cylindrical pores orientated parallel to the compression direction decreases linearly with increasing porosity. For the porous copper whose pore axes are perpendicular to the compressive direction, the compressive yield strength slightly decreases in the porosity range up to 30% and then decreases significantly with increasing porosity. The compressive stress–strain curves depend on the compressive direction with respect to the pore direction, which are due to the stress concentration around the pores and the buckling of the copper between the pores. From two different types of stress–strain curve, the energy absorption capacity of the porous copper with the pores parallel to the compressive direction is higher than that perpendicular to the compressive direction at a given porosity.

Anisotropic compressive properties of porous copper produced by unidirectional solidification

Effect of transference velocity and hydrogen pressure on porosity and pore morphology of lotus-type porous copper fabricated by a continuous casting technique

Lotus-type porous metals whose long cylindrical pores are aligned in one direction were fabricated by unidirectional solidification in a pressurized gas atmosphere. The pores are formed as a result of precipitation of supersaturated gas when liquid metal is solidified. The lotus-type porous metals with homogeneous size and porosity of the evolved pores produced by a mould casting technique are limited to the metals with high thermal conductivity. On the other hand, the pores with inhomogeneous pore size and porosity are evolved for metals and alloys with low thermal conductivity such as stainless steel. In order to obtain uniform pore size and porosity, a new “continuous zone melting technique” was developed to fabricate long rod- and plate-shape porous metals and alloys even with low thermal conductivity. Mechanical properties of tensile and compressive strength of lotus-type porous metals and alloys are described together with internal friction, elasticity, thermal conductivity and sound absorption characteristics. All the physical properties exhibit significant anisotropy. Lotus-type porous iron fabricated using a pressurized nitrogen gas instead of hydrogen exhibits superior strength.

Fabrication of Lotus‐type Porous Metals and their Physical Properties

Lotus-type porous magnesium with cylindrical pores aligned unidirectionally was fabricated by the unidirectional solidification of molten magnesium under pressurized hydrogen atmosphere. The apparent attenuation coefficient of the free vibration of lotus-type porous magnesium was measured by hammering–vibration–damping tests, which revealed that the apparent attenuation coefficient increases with increase in porosity, i.e., the damping capacity of lotus magnesium is higher than that of non-porous magnesium. The mechanism of high damping capacity was analyzed by using the Fourier transform technique, which revealed that various vibration modes of high frequency are excited by a hammering. The excited vibrations of high frequency enhance the damping capacity of lotus-type porous magnesium.

Soong-Keun Hyun

Papers

Anisotropic mechanical properties of porous copper fabricated by unidirectional solidification

Anisotropic compressive properties of porous copper produced by unidirectional solidification

Effect of transference velocity and hydrogen pressure on porosity and pore morphology of lotus-type porous copper fabricated by a continuous casting technique

Fabrication of Lotus‐type Porous Metals and their Physical Properties

Vibration–damping capacity of lotus-type porous magnesium