Search results for "FN"

A comparative study of fatigue behaviour of flax/epoxy and glass/epoxy composites

2012

Experimental investigations on flax and glass fabrics reinforced epoxy specimens, i.e. FFRE and GFRE, submitted to fatigue tests are presented in this paper. Samples having [0/90]3S and [±45]3S stacking sequences, with similar fibre volume fractions have been tested under tension–tension fatigue loading. The specific stress-number of cycles to failure (S–N) curves, show that for the [0/90]3S specimens, FFRE have lower fatigue endurance than GFRE, but the [±45]3S FFRE specimens offer better specific fatigue endurance than similar GFRE, in the studied life range (<2 × 10^6). Overall, the three-stage stiffness degradation is observed in all cases except for [0/90]3S FFRE specimens, which prese…

Mechanical properties of Macadamia nutshell powder and PLA bio-composites

2016

AbstractA study on the mechanical properties of Macadamia nutshell powder/PLA bio-composites is presented in this paper. The effects of powder weight content, powder condition and processing methods are investigated with the aid of Design of Experiments. It is shown from the results that both the stiffness and strength are dependent on the weight content of Macadamia nutshell powders. The elastic modulus increases 9.8% when the Macadamia nutshell powder content is 40%. Both flexural and tensile strengths decrease with increasing Macadamia nutshell powder content. On average, when the Macadamia nutshell powder content is 40%, the decreases in the flexural and tensile strengths are 42 and 63%…

Viscoelastic properties of the Achilles tendon in vivo

2013

It has been postulated that human tendons are viscoelastic and their mechanical properties time-dependent. Although Achilles tendon (AT) mechanics are widely reported, there is no consensus about AT viscoelastic properties such as loading rate dependency or hysteresis, in vivo. AT force-elongation characteristics were determined from 14 subjects in an ankle dynamometer at different loading rates using motion capture assisted ultrasonography. AT stiffness and elongation were determined between 10 – 80% of maximum voluntary contraction (MVC) force at fast and slow loading rates. As subjects were unable to consistently match the target unloading rate in the slow condition, AT hysteresis was on…

Meshless meso-modeling of masonry in the computational homogenization framework

2017

In the present study a multi-scale computational strategy for the analysis of structures made-up of masonry material is presented. The structural macroscopic behavior is obtained making use of the Computational Homogenization (CH) technique based on the solution of the Boundary Value Problem (BVP) of a detailed Unit Cell (UC) chosen at the mesoscale and representative of the heterogeneous material. The attention is focused on those materials that can be regarded as an assembly of units interfaced by adhesive/cohesive joints. Therefore, the smallest UC is composed by the aggregate and the surrounding joints, the former assumed to behave elastically while the latter show an elastoplastic soft…

Parameters influencing the stiffness of composites reinforced by carbon nanotubes – A numerical–analytical approach

2014

Abstract Due to their high stiffness and strength, as well as their electrical conductivity, carbon nanotubes are under intense investigation as fillers in polymer matrix composites. The nature of the carbon nanotube/polymer bonding and the curvature of the carbon nanotubes may strongly reduce the reinforcing effect of the carbon nanotubes when added to a matrix to create composites. Here the effects of carbon nanotube waviness and the interaction with the matrix on the stiffness of the composite are investigated. Using a mixed numerical–analytical model, a parametric study of the waviness and volume fraction influence of CNTs on the elastic behavior of the nanocomposite is presented. The m…

Acoustic modes in metallic nanoparticles: atomistic versus elasticity modeling

2009

The validity of the linear elasticity theory is examined at the nanometer scale by investigating the vibrational properties of silver and gold nanoparticles whose diameters range from about 1.5 to 4 nm. Comparing the vibration modes calculated by elasticity theory and atomistic simulation based on the Embedded Atom Method, we first show that the anisotropy of the stiffness tensor in elastic calculation is essential to ensure a good agreement between elastic and atomistic models. Second, we illustrate the reduction of the number of vibration modes due to the diminution of the number of atoms when reducing the nanoparticles size. Finally, we exhibit a breakdown of the frequency-spectra scalin…

Mechanical characterization of dry asphalt rubber concrete for base layers by means of the four bending points tests

2012

The mechanical characterisation of the asphalt concrete in terms of both the fatigue resistance and the stiffness modulus is necessary to use any design method of the flexible road pavements. Even more the determination of these mechanical properties is necessary if the asphalt concrete investigated is an innovative material as a dry asphalt rubber concrete DARC (i.e. a bituminous mixture with rubber via dry process). Such material is less known and investigated than the asphalt rubber concrete via wet process, even if its application implies peculiar economical and environmental advantages such as no specialized equipment or significant plant modifications and large quantity of recycled wa…

Short-range order around Er3+ in silica waveguides containing aluminium, titanium and hafnium

2006

Er3+-doped silica waveguides, co-doped with aluminium, titanium, and hafnium oxides, were prepared using the sol-gel method and dip-coating processing. Here, we present a characterisation of the local environment around Er3+ ions, as determined from the Er L3-edge extended X-ray absorption fine structure (EXAFS) measurements performed at ESRF (France). The first coordination shell is composed of 5-6 oxygen atoms at distances ~2.32-2.35 A , slightly varying as a function of the modifier oxide. Er3+ nearest neighbors distance does not show a significant compositional dependence. On the contrary, outer shells analysis shows significant differences: Al2O3 doping (less than 2% mol) induces an or…

Membrane Stiffness of Animal Cells Challenged by Osmotic Stress

2006

Buckling of a coating strip of finite width bonded to elastic half-space

2008

AbstractA solution for buckling of a stiff strip of finite width bonded to a compliant elastic half-space and subjected to uniform axial compression is presented. Approximate semi-analytical and finite element solutions are obtained and compared with a two-dimensional case of a plate on elastic foundation. The comparison demonstrates that the two-dimensional solution can be applied to predict the buckling wavelength and critical compressive strain when the width of the strip is equal to or larger than the buckling wavelength. For narrow strips, the wavelength is smaller and critical strain is higher than that of a plate on foundation.