Elastic modulus

About: Elastic modulus is a research topic. Over the lifetime, 33153 publications have been published within this topic receiving 810247 citations.

Pseudo Hall-Petch strength reduction in polycrystalline graphene.

Abstract: The fracture of polycrystalline graphene is explored by performing molecular dynamics simulations with realistic finite-grain-size models, emphasizing the role of grain boundary ends and junctions. The simulations reveal a ∼50% or more strength reduction due to the presence of the network of boundaries between polygonal grains, with cracks preferentially starting at the junctions. With a larger grain size, a surprising systematic decrease of tensile strength and failure strain is observed, while the elastic modulus rises. The observed crack localization and strength behavior are well-explained by a dislocation-pileup model, reminiscent of the Hall–Petch effect but coming from different underlying physics.

Standardized Nanomechanical Atomic Force Microscopy Procedure (SNAP) for Measuring Soft and Biological Samples.

Abstract: We present a procedure that allows a reliable determination of the elastic (Young's) modulus of soft samples, including living cells, by atomic force microscopy (AFM). The standardized nanomechanical AFM procedure (SNAP) ensures the precise adjustment of the AFM optical lever system, a prerequisite for all kinds of force spectroscopy methods, to obtain reliable values independent of the instrument, laboratory and operator. Measurements of soft hydrogel samples with a well-defined elastic modulus using different AFMs revealed that the uncertainties in the determination of the deflection sensitivity and subsequently cantilever's spring constant were the main sources of error. SNAP eliminates those errors by calculating the correct deflection sensitivity based on spring constants determined with a vibrometer. The procedure was validated within a large network of European laboratories by measuring the elastic properties of gels and living cells, showing that its application reduces the variability in elastic moduli of hydrogels down to 1%, and increased the consistency of living cells elasticity measurements by a factor of two. The high reproducibility of elasticity measurements provided by SNAP could improve significantly the applicability of cell mechanics as a quantitative marker to discriminate between cell types and conditions.

The Young's modulus of feather keratin

Abstract: The flexural stiffness of the rachis varies along the length of a primary feather, between primaries and between species; the possible contribution of variations in the longitudinal Young's modulus of feather keratin to this was assessed. Tensile tests on compact keratin from eight species of birds belonging to different orders showed similar moduli (mean E=2.50 GPa) in all species apart from the grey heron (E=1.78 GPa). No significant differences were seen in the modulus of keratin from primaries 7­10 in any species. There was a systematic increase in the modulus distally along the length of the rachis from swan primary feathers. Dynamic bending tests on swan primary feather rachises also showed that the longitudinal elastic modulus increases with increasing frequency of bending over the range 0.1­10 Hz and decreases monotonically with increasing temperature over the range -50 to +50 °C. The position-, frequency- and temperature-dependent variations in the modulus are, however, relatively small. It is concluded that, in the species studied, the flexural stiffness of the whole rachis is principally controlled by its cross-sectional morphology rather than by the material properties of the keratin.

Evaluation of interphase properties in a cellulose fiber-reinforced polypropylene composite by nanoindentation and finite element analysis

Abstract: The hardness and elastic modulus of the cellulose fiber and polypropylene (PP) matrix in a cellulose fiber-reinforced PP composite were investigated by nanoindentation with a continuous stiffness technique. Nanoindentation with different indentation depths and spacings was conducted to measure hardness and elastic modulus in the interphase region, which was modified by maleic anhydride-grafted PP and γ-amino propyltrimethoxy silane (γ-APS) sizing. A line of indents was produced from the fiber to the matrix. There was a gradient of hardness and modulus across the interphase region. The distinct properties of the transition zone were revealed by 1–4 indents, depending on nanoindentation depth and spacing. Based on the results of nanoindentation, it was assumed that the width of the property transition zone is less than 1 μm. However, three dimensional finite element analysis shows that even a perfect interface without property transition has almost same interphase width as that measured by nanoindentation. Using existing nanoindentation techniques, it will be difficult to calculate exact mechanical properties without the effect of neighboring material property in at least 8 times smaller region than indent size.