Elastic modulus

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

Soft-matter composites with electrically tunable elastic rigidity

Abstract: We use a phase-changing metal alloy to reversibly tune the elastic rigidity of an elastomer composite. The elastomer is embedded with a sheet of low-melting-point Field’s metal and an electric Joule heater composed of a serpentine channel of liquid-phase gallium‐indium‐tin (Galinstan R ) alloy. At room temperature, the embedded Field’s metal is solid and the composite remains elastically rigid. Joule heating causes the Field’s metal to melt and allows the surrounding elastomer to freely stretch and bend. Using a tensile testing machine, we measure that the effective elastic modulus of the composite reversibly changes by four orders of magnitude when powered on and off. This dramatic change in rigidity is accurately predicted with a model for an elastic composite. Reversible rigidity control is also accomplished by replacing the Field’s metal with shape memory polymer. In addition to demonstrating electrically tunable rigidity with an elastomer, we also introduce a new technique to rapidly produce soft-matter electronics and multifunctional materials in several minutes with laser-patterned adhesive film and masked deposition of liquid-phase metal alloy. (Some figures may appear in colour only in the online journal)

Modelling drying shrinkage in reconstructed porous materials: application to porous Vycor glass

Abstract: A three-dimensional representation of the microstructure of porous Vycor glass was generated from a transmission electron micrograph, and was analysed to compute the locations of all capillary-condensed water as a function of relative humidity. On solid surfaces where capillary-condensed water was not present, an adsorbed water layer, whose thickness is a function of relative humidity, was placed. As a function of relative humidity, fixed pressures were specified in all capillary-condensed water, and the change in specific surface free energy with relative humidity was taken into account for the adsorbed water layers. New finite-element codes were developed to determine the drying shrinkage, in response to the changes in the specific surface free energy of the adsorbed water layers and to the fixed pressures in the capillary condensed water. Existing finite-element and finite-difference codes were used to evaluate the elastic moduli, the electrical and thermal conductivity, and the fluid permeability of the material. Bulk properties such as fluid permeability and electrical and thermal conductivity agreed well with experiment. By adjusting the elastic moduli of the solid backbone, which are not experimentally determined quantities, the computed porous glass elastic moduli, and computed low and high relative humidity shrinkage all agreed well with experimental values. At intermediate relative humidities, the agreement for shrinkage was worse, partly due to inaccuracies in the simulated water desorption curve, and partly due to the fact that water-induced swelling of the solid backbone, an effect that is probably present in the real material, was not taken into account in the model computations.

Measurements of the material properties of metal nanoparticles by time-resolved spectroscopy

Abstract: An important aim of nanoparticle research is to understand how the properties of materials depend on their size and shape. In this Invited Article I describe how time-resolved spectroscopy can be used to measure physical properties of nanometre sized objects such as the characteristic time scales for electron–phonon coupling and heat dissipation, and their elastic moduli. The electron–phonon coupling and heat dissipation measurements are important for applications of particles that involve conduction of heat or electricity. On the other hand, the elastic moduli studies provide fundamental information about the properties of nanomaterials. The results of these experiments show that nanometre sized particles can have very different properties compared to the corresponding bulk material. For example, we have recently shown that gold nanorods produced by wet chemical methods have much smaller elastic moduli (an 18% decrease in Young’s modulus) compared to bulk gold.

Electronic, elastic, and fracture properties of trialuminide alloys: Al3Sc and Al3Ti

Abstract: The electronic mechanism behind the brittle fracture of trialuminide alloys is investigated using the full-potential linearized augmented plane-wave (FLAPW) total-energy method within the local density functional approach. To this end, the bulk phase stability, the elastic constants, the anti-phase boundary (APB) energy, the superlattice intrinsic stacking fault (SISF) energy, and the cleavage energy on different crystallographic planes have been determined. A small energy difference (=0.10 eV/unit formula) is found between the DO22 and L12 structures of Al3Ti. In general, the trialuminide alloys have large elastic modulus, small Poisson's ratio, and small shear modulus to bulk modulus ratio. An extremely high APB energy (=670 mJ/m2) on the (111) plane is found for Al3Sc, indicating that the separation between ½(110) partials of a (110)(111) superdislocation is small. Since the total superdislocation has to be nucleated essentially at the same time, a high critical stress factor for dislocation emission at the crack tip is suggested. The high APB energy on the (111) plane is attributed to the directional bonding of Sc(d-electron)-Al(p-electron). The same type of directional bonds is also found for Al3Ti. In addition, moderately high values of SISF energy (=265 mJ/m2) on the (111) plane and APB energy (=450 mJ/m2) on the (100) plane are found for Al3Sc. The brittle fracture of trialuminide alloys is attributed to the higher stacking fault energies and a lower cleavage strength compared to those of a ductile alloy (e.g., Ni3Al). While the (110) surface has the highest surface energy, the cleavage strength (=19 GPa) of Al3Sc is found to be essentially independent of the crystallographic planes. The directional Sc—Al bond becomes even stronger on the (110) surface, which may explain the preferred (110) type cleavage observed by experiment.