Elastic modulus

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

Size effects in mechanical deformation and fracture of cantilevered silicon nanowires.

Abstract: Elastic modulus and fracture strength of vertically aligned Si [111] nanowires (o ) 100-700 nm) in an as-grown state have been measured using a new, multipoint bending protocol in an atomic force microscope. All wires showed linear elastic behavior, spring constants which scale with (length) 3 , and brittle failure at the wire-substrate junction. The “effective” Young’s modulus increased slightly (100 f 160-180 GPa) as wire diameter decreased, but fracture strength increased by 2-3 orders of magnitude (MPa f GPa). These results indicate that vapor-liquid-solid grown wires are relatively free of extended volume defects and that fracture strength is likely controlled by twinning and interfacial effects at the wire foot. Small wires (100 nm) grown with a colloidal catalyst were the best performers with high modulus (∼180 GPa) and fracture stress >1 GPa. One-dimensional nano-objects (nanowires, tubes, rods, springs, etc.) have attracted considerable interest lately as building blocks for electromechanical systems (oscillators, sensors, actuators), circuit interconnects, and composite materials of the future. Manipulation and exploitation of these new structures for technological applications requires detailed knowledge of material properties at the single nanostructure level. Previous studies have shown that the “effective” elasticity, strength, and plasticity of materials can all be influenced by size, shape, and “surface effects” (surface stress, oxide layers, roughness, and defects) when nanometer dimensions are involved. 1-5 Given the importance of such issues, it is no surprise that many interrogation techniques have been used to explore these effects: nanoindentation, tensile/bending (static and dynamic) tests, and resonant excitation. 1-16 In particular, atomic force microscope (AFM)based bending experiments on nanobeams and nanowires (NW) are very popular. These approaches typically measure the force required to deform a “beam” fabricated via topdown techniques, 6,7 NWs that have been artificially “fixed” to a surface with metallic pads, 8 or NWs positioned across a gap 9-12 (with and without surface pinning of the wire ends).

Effect of aggregate properties on the strength and stiffness of lightweight concrete

Abstract: An experimental program was carried out to obtain the compressive strengths and elastic moduli of cold-bonded pelletized lightweight aggregate concretes. Three types of aggregates were made with different fly ash contents. Experimental data were analyzed statistically. Test results of multivariate analysis of variance (MANOVA) with 95% confidence level ( α =0.05) show that the properties of lightweight aggregates and the water/binder ratio are two significant factors affecting the compressive strength and elastic modulus of concrete.

Elastic modulus of lignin as related to moisture content

Abstract: The Young's and shear moduli of two lignins have been measured at several moisture contents. Cylindrical test specimens moulded from periodate and Klason lignin powders were conditioned to the required moisture contents and tested in tension and torsion. The Young's modulus of periodate lignin increased linearly from 3.1x109 to 6.7x109 Pa, and the shear modulus from 1.2x109 to 2.1x109 Pa as the moisture content of the lignin decreased from 12 to 3.6%. Klason lignin showed similar behaviour but its moduli were always much lower. This was probably a consequence of the more drastic alteration undergone by the Klason lignin during its isolation from the wood cell wall.