sajjad raeisi | Purdue University (original) (raw)
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Papers by sajjad raeisi
Rapid prototyping (RP) has been a promising technique for producing tissue engineering scaffolds ... more Rapid prototyping (RP) has been a promising technique for producing tissue engineering scaffolds which mimic
the behavior of host tissue as properly as possible. Biodegradability, agreeable feasibility of cell growth, and migration parallel to mechanical properties, such as strength and energy absorption, have to be considered in design
procedure. In order to study the effect of internal architecture on the plastic deformation and failure pattern, the
architecture of triply periodic minimal surfaces which have been observed in nature were used. P and D surfaces
at 30% and 60% of volume fractions were modeled with 3 ∗ 3 ∗ 3 unit cells and imported to Objet EDEN 260 3-D
printer. Models were printed by VeroBlue FullCure 840 photopolymer resin. Mechanical compression test was
performed to investigate the compressive behavior of scaffolds. Deformation procedure and stress– strain curves
were simulated by FEA and exhibited good agreement with the experimental observation. Current approaches
for predicting dominant deformation mode under compression containing Maxwell's criteria and scaling laws
were also investigated to achieve an understanding of the relationships between deformation pattern and mechanical properties of porous structures. It was observed that effect of stress concentration in TPMS-based scaffol ds resu ltant by heter ogene ous mass dist ribu tion, pa rticu larl y at lower volum e fracti ons, led to a dif feren t
behavior from that of typical cellular materials. As a result, although more parameters are considered for determining dominant deformation in scaling laws, two mentioned approaches could not exclusively be used to compare the mechanical response of cellular materials at the same volume fraction.
Macroscopic mechanical properties of metal foams originate from the deformation of forming cells ... more Macroscopic mechanical properties of metal foams originate from the deformation of forming cells which happens on a micro scale. In this sense, the geometry of cells as well as the thickness and property of cell walls play a role in determining overall mechanical properties. Using simulation methods combined with some experimental tests, the inter-relationship between the micro scale deformation and the macro scale properties is investigated in this paper. In the first part of the work, the effect of relative density on the mechanical properties of closed-cell aluminum foam is investigated by numerical methods, and the results are compared with analytical predictions and experimental data. In the second part, the effect of cell topology, including cell shape and cell size, on the material behavior is investigated for aluminum foams, regardless of relative density. It is shown that cell shape causes some changes in macroscopic material behavior, which can be explained by its effect on the pattern of deformation and local failure in the material. Different mechanisms of deformation at the cell level are considered in connection with closed-cell aluminum foams. And finally, in the third part, different patterns of failure are investigated on different scales. The deformation and failure at the cell level cause localization on the macro scale. The cell shape and the inhomogeneity of the foam structure are investigated as the primary factors affecting the deformation and failure modes, and the results give some deeper understanding about the effect of cell shape on mechanical behavior. Also, some experimental tests are carried out to validate the numerical results.
Rapid prototyping (RP) has been a promising technique for producing tissue engineering scaffolds ... more Rapid prototyping (RP) has been a promising technique for producing tissue engineering scaffolds which mimic
the behavior of host tissue as properly as possible. Biodegradability, agreeable feasibility of cell growth, and migration parallel to mechanical properties, such as strength and energy absorption, have to be considered in design
procedure. In order to study the effect of internal architecture on the plastic deformation and failure pattern, the
architecture of triply periodic minimal surfaces which have been observed in nature were used. P and D surfaces
at 30% and 60% of volume fractions were modeled with 3 ∗ 3 ∗ 3 unit cells and imported to Objet EDEN 260 3-D
printer. Models were printed by VeroBlue FullCure 840 photopolymer resin. Mechanical compression test was
performed to investigate the compressive behavior of scaffolds. Deformation procedure and stress– strain curves
were simulated by FEA and exhibited good agreement with the experimental observation. Current approaches
for predicting dominant deformation mode under compression containing Maxwell's criteria and scaling laws
were also investigated to achieve an understanding of the relationships between deformation pattern and mechanical properties of porous structures. It was observed that effect of stress concentration in TPMS-based scaffol ds resu ltant by heter ogene ous mass dist ribu tion, pa rticu larl y at lower volum e fracti ons, led to a dif feren t
behavior from that of typical cellular materials. As a result, although more parameters are considered for determining dominant deformation in scaling laws, two mentioned approaches could not exclusively be used to compare the mechanical response of cellular materials at the same volume fraction.
Macroscopic mechanical properties of metal foams originate from the deformation of forming cells ... more Macroscopic mechanical properties of metal foams originate from the deformation of forming cells which happens on a micro scale. In this sense, the geometry of cells as well as the thickness and property of cell walls play a role in determining overall mechanical properties. Using simulation methods combined with some experimental tests, the inter-relationship between the micro scale deformation and the macro scale properties is investigated in this paper. In the first part of the work, the effect of relative density on the mechanical properties of closed-cell aluminum foam is investigated by numerical methods, and the results are compared with analytical predictions and experimental data. In the second part, the effect of cell topology, including cell shape and cell size, on the material behavior is investigated for aluminum foams, regardless of relative density. It is shown that cell shape causes some changes in macroscopic material behavior, which can be explained by its effect on the pattern of deformation and local failure in the material. Different mechanisms of deformation at the cell level are considered in connection with closed-cell aluminum foams. And finally, in the third part, different patterns of failure are investigated on different scales. The deformation and failure at the cell level cause localization on the macro scale. The cell shape and the inhomogeneity of the foam structure are investigated as the primary factors affecting the deformation and failure modes, and the results give some deeper understanding about the effect of cell shape on mechanical behavior. Also, some experimental tests are carried out to validate the numerical results.