Elastic modulus

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

Predicting the elastic modulus of natural fibre reinforced thermoplastics

Abstract: Natural fibre reinforced thermoplastics (NFRT) are increasingly used in a variety of commercial applications, but there has been little theoretical modeling of structure/property relationships in these materials. In this study, micromechanical models available in the short fibre composites literature were used to predict the stiffness of some commercially important natural fibre composite formulations. Also included are equations that correct the Young’s modulus of natural fibres for changes in moisture content and density that occur as a result of processing. Hemp fibres, hardwood fibres, rice hulls, and E-glass fibres were blended into high-density polyethylene in mass fractions of 10–60-wt%. The Young’s modulus of these composites was compared to theoretical values generated by the rule of mixtures, Halpin–Tsai, Nairn’s generalized shear-lag analysis and Mendels et al. stress transfer (micromechanical) models. Based on a sum of errors squared criterion, the Halpin–Tsai equation was found to predict the experimental data most accurately for the NFRT created for this study.

A one-dimensional model for superelastic shape-memory alloys with different elastic properties between austenite and martensite

Abstract: The present work addresses a one-dimensional model able to reproduce the shape-memory-alloy superelastic behavior, taking into account the different elastic properties between austenite and martensite. The model is based on a single scalar internal variable, the martensite fraction, for which evolutionary equations in rate form are proposed. The dependency of the elastic modulus in terms of the martensite fraction is computed through different homogenization techniques. Integration in time leads to the time-discrete evolutionary equations, for which a detailed analysis in terms of admissible roots is presented, together with the expression of the consistent tangent modulus. The solution of the time-discrete model is approached through a return map algorithm, properly modified for the case of phase transitions of the type occurring in shape-memory materials. Finally, the ability of the model to simulate one-dimensional experimental data is assessed.

Local elasticity map and plasticity in a model Lennard-Jones glass.

Abstract: In this work we calculate the local elastic moduli in a weakly polydispersed two-dimensional Lennard-Jones glass undergoing a quasistatic shear deformation at zero temperature. The numerical method uses coarse-grained microscopic expressions for the strain, displacement, and stress fields. This method allows us to calculate the local elasticity tensor and to quantify the deviation from linear elasticity (local Hooke's law) at different coarse-graining scales. From the results a clear picture emerges of an amorphous material with strongly spatially heterogeneous elastic moduli that simultaneously satisfies Hooke's law at scales larger than a characteristic length scale of the order of five interatomic distances. At this scale, the glass appears as a composite material composed of a rigid scaffolding and of soft zones. Only recently calculated in nonhomogeneous materials, the local elastic structure plays a crucial role in the elastoplastic response of the amorphous material. For a small macroscopic shear strain, the structures associated with the nonaffine displacement field appear directly related to the spatial structure of the elastic moduli. Moreover, for a larger macroscopic shear strain we show that zones of low shear modulus concentrate most of the strain in the form of plastic rearrangements. The spatiotemporal evolution of this local elasticity map and its connection with long term dynamical heterogeneity as well as with the plasticity in the material is quantified. The possibility to use this local parameter as a predictor of subsequent local plastic activity is also discussed.

Single‐crystal elastic properties of the spinel phase of Mg2SiO4

Abstract: The single-crystal elastic moduli of the spinel (gamma) phase of Mg2SiO4 have been experimentally determined from Brillouin spectroscopy at ambient conditions. They are C11 = 327, C44 = 126, and C12 = 112 (GPa) yielding a bulk modulus of 184. and a shear modulus of 119 GPa. This value of bulk modulus is lower than expected from previous measurements. The elastic properties of the spinel and modified spinel (beta) phases of Mg2SiO4 are quite similar with the greatest differences related to the c axis of the beta which is relatively soft under compression. The polycrystal 1ine acoustic velocities differ by only 1% for these two phases. Thus there should be no seismic discontinuity associated with the beta to gamma phase transition in the mantle. The similarity of elastic properties of these two phases suggests that effects of pressure, temperature, and iron content on the elastic properties should be similar for both phases. Estimates of the effect of iron content are made from the extant data on fayalite spinel in conjunction with the data presented here. The derivatives of elastic moduli with respect to iron content are very similar to those observed for the olivine phase. Based on comparisons with aluminate analogue compositions in the spinel structure, there is no justification to predict the pressure or temperature derivatives of the elastic moduli of these high pressure phases at this time.