Microstructure-based modeling of elastic functionally graded materials: One dimensional case

Functionally graded materials (FGMs) are two-phase composites with continuously changing microstructure adapted to performance requirements. Traditionally, the overall behavior of FGMs has been determined using local averaging techniques or a given smooth variation of material properties. Although these models are computationally efficient, their validity and accuracy remain questionable, since a link with the underlying microstructure (including its randomness) is not clear. In this paper, we propose a modeling strategy for the linear elastic analysis of FGMs systematically based on a realistic microstructural model. The overall response of FGMs is addressed in the framework of stochastic Hashin-Shtrikman variational principles. To allow for the analysis of finite bodies, recently introduced discretization schemes based on the Finite Element Method and the Boundary Element Method are employed to obtain statistics of local fields. Representative numerical examples are presented to compare the performance and accuracy of both schemes. To gain insight into similarities and differences between these methods and to minimize technicalities, the analysis is performed in the one-dimensional setting.Comment: 33 pages, 14 figure

Experimental characterisation of porcine subcutaneous adipose tissue under blunt impact up to irreversible deformation

A deeper understanding of the mechanical characteristics of adipose tissue under large deformation is important for the analysis of blunt force trauma, as adipose tissue alters the stresses and strains that are transferred to subjacent tissues. Hence, results from drop tower tests of subcutaneous adipose tissue are presented (i) to characterise adipose tissue behaviour up to irreversible deformation, (ii) to relate this to the microstructural configuration, (iii) to quantify this deformation and (iv) to provide an analytical basis for computational modelling of adipose tissue under blunt impact. The drop tower experiments are performed exemplarily on porcine subcutaneous adipose tissue specimens for three different impact velocities and two impactor geometries. An approach based on photogrammetry is used to derive 3D representations of the deformation patterns directly after the impact. Median values for maximum impactor acceleration for tests with a flat cylindrical impactor geometry at impact velocities of 886~mm/s, 1253~mm/s and 2426~mm/s amount to 61.1~g, 121.6~g and 264.2~g, respectively, whereas thickness reduction of the specimens after impact amount to 16.7%, 30.5% and 39.3%, respectively. The according values for tests with a spherically shaped impactor at an impact velocity of 1253~mm/s are 184.2~g and 78.7%. Based on these results, it is hypothesised that, in the initial phase of a blunt impact, adipose tissue behaviour is mainly governed by the behaviour of the lipid inside the adipocytes, whereas for further loading, contribution of the extracellular collagen fibre network becomes more dominant

Synthesis and spectroscopic characterization of some chromanochalcones and their dihydro derivatives

Synthesis of naturally occurring 6-(α,β-dihydrocinnamoyl)-3,4-dihydro-2H-chromanes has been carried out by the reaction of 6-acetyl-3,4-dihydro-2H--chromanes with methoxybenzaldehydes followed by hydrogenation of the resulting 6-cinnamoyl-3,4-dihydro-2H--chromanes

Bioactive Phenolics from Carthamus lanatus L.

Two flavonoid aglycons, eight flavonoid glycosides, chlorogenic acid and syringin were isolated from aerial parts of Carthamus lanatus. Isorhamnetin 3-O-β-D-glucoside and chlorogenic acid were found for the first time in the genus Carthamus and respectively, quercimeritrin, astragalin, kaempferol 3-O-β-D-sophoroside and syringin in the species. The ethyl acetate fraction of the methanol extract exhibited a higher antioxidant activity than the butanol fraction measured by the α,α-diphenyl-β -picrazylhydrazyl (DPPH) free radical scavenging assay. Cytotoxicity and antioxidant activities of the main constituent, luteolin 7-O-β-D-glucoside, were evaluated