Search results for "Elasticity"
showing 10 items of 736 documents
Coffee grounds as filler for pectin: Green composites with competitive performances dependent on the UV irradiation.
2017
Novel composite bioplastics were successfully prepared by filling pectin matrix with treated coffee grounds. The amount of coffee dispersed into the pectin was changed within a wide filler range. The morphology of the pectin/coffee hybrid films was studied by microscopic techniques in order to investigate their mesoscopic structure as well as the sizes distribution of the particles dispersed into the matrix. The micrographs showed that the coffee grounds are uniformly dispersed within the polymeric matrix. The morphological characteristics of the biocomposite films were correlated to their properties, such as wettability, water uptake, thermal behavior and mechanical performances. Dynamic m…
Rippling of two-dimensional materials by line defects
2020
Two-dimensional materials and their mechanical properties are known to be profoundly affected by rippling deformations. However, although ripples are fairly well understood, less is known about their origin and controlled modification. Here, motivated by recent reports of laser-controlled creation of line defects in graphene, we investigate how line defects could be used to control rippling in graphene and other two-dimensional materials. By sequential multi-scale coupling of density-functional tight-binding and continuum elasticity simulations, we quantify the amount of rippling when the number and the cumulative length of the line defects increase. Simulations show that elastic sheets wit…
Experimental Characterization of the Human Meniscal Tissue
2018
The meniscus plays a critical role in load transmission, stability and energy dissipation in the knee joint. Loss of the meniscus leads to joint degeneration and osteoarthritis. In a number of cases replacement of the resected meniscal tissue by a synthetic implant might avoid the articular cartilage degeneration. None of the available implants presents optimal biomechanics characteristic due to the fact the biomechanics functionality of the meniscus is not yet fully understood. Mimicking the native biomechanical characteristics of the menisci seems to be the key factor in meniscus replacement functioning. This is extremely challenging due to its complex inhomogeneous microstructure, the la…
The influence of the rubber carboxyl functionality on the processability and properties of solid rubber modified epoxy mixtures
2005
A high molecular weight, carboxyl functionalised solid rubber was added to an epoxy resin-aromatic amino system developed for autoclave curing of honeycomb core composite structures. The achievement of an optimal balance of viscous flow and viscoelasticity of the resin, by controlling the nature and extent of cross-linking of the functionalised rubber, was proposed as a route to void-free honeycomb skins. The aim of the present investigation is to understand how the concentration of carboxylic groups of the rubber, prereacted with one of the epoxy monomers, affects the matrix resin flow properties. The concentration of carboxyl groups was changed by reacting them with a monofunctional epoxy…
Two multilayered plate models with transverse shear warping functions issued from three dimensional elasticity equations
2014
Abstract A multilayered plate theory which uses transverse shear warping functions is presented. Two methods to obtain the transverse shear warping functions from three-dimensional elasticity equations are proposed. The warping functions are issued from the variations of transverse shear stresses computed at specific points of a simply supported plate. The first method considers an exact 3D solution of the problem. The second method uses the solution provided by the model itself: the transverse shear stresses are computed integrating equilibrium equations. Hence, an iterative process is applied, the model is updated with the new warping functions, and so on. Once the sets of warping functio…
Limits of stability in supported graphene nanoribbons subject to bending
2016
Graphene nanoribbons are prone to in-plane bending even when supported on flat substrates. However, the amount of bending that ribbons can stably withstand remains poorly known. Here, by using molecular dynamics simulations, we study the stability limits of 0.5-1.9 nm wide armchair and zigzag graphene nanoribbons subject to bending. We observe that the limits for maximum stable curvatures are below ~10 deg/nm, in case the bending is externally forced and the limit is caused by buckling instability. Furthermore, it turns out that the limits for maximum stable curvatures are also below ~10 deg/nm, in case the bending is not forced and the limit arises only from the corrugated potential energy…
Sensitivity analysis for discretized unilateral plane elasticity problem
1992
Abstract Numerical realization of optimal shape design problems requires gradient information which is used in minimization procedures. There are several possibilities for obtaining this information. Here we present a method, based on the use of the material derivative approach, applied to the finite element discretization of the problem. The advantage of this approach is that is gives the exact values of gradient and it can be very easily implemented on computers. We apply this method in the case of contact problems, where the situation is more involved compared with the case of elasticity problems with classical boundary conditions. We concentrate on a special choice of the cost functiona…
On the influence of the initial ramp for a correct definition of the parameters of fractional viscoelastic materials
2014
Creep and/or Relaxation tests on viscoelastic materials show a power-law trend. Based upon Boltzmann superposition principle the constitutive law with a power-law kernel is ruled by the Caputo's fractional derivative. Fractional constitutive law posses a long memory and then the parameters obtained by best fitting procedures on experimental data are strongly influenced by the prestress on the specimen. As in fact during the relaxation test the imposed history of deformation is not instantaneously applied, since a unit step function may not be realized by the test machine. Usually an initial ramp is present in the deformation history and the time at which the deformation attains the maximum …
Stochastic dynamics of linear elastic trusses in presence of structural uncertainties (virtual distortion approach)
2004
Structures involving uncertainties in material and/or in geometrical parameters are referred to as uncertain structures. Reliability analysis of such structures strongly depends on variation of parameters and probabilistic approach is often used to characterize structural uncertainties. In this paper dynamic analysis of linearly elastic system in presence of random parameter variations will be performed. In detail parameter fluctuations have been considered as inelastic, stress and parameter dependent superimposed strains. Analysis is then carried out via superposition principle accounting for response to external agencies and parameter dependent strains. Proposed method yields asymptotic s…
Health monitoring of high performance composite pressure vessels,
2018
International audience; The most important form of damage in carbon fiber reinforced composite pressure vessels is the failure of the fibers however the rate of fiber failure is controlled by the viscoelastic nature of the matrix, which determines overall in-service lifetimes. This type of damage is very different from that encountered with metal pressure vessels and requires a detailed understanding in order to ensure reliability. Innovative proof testing methods based on these processes are necessary. The damage processes and the means of quantifying them are discussed. Their reliability under pressure over periods of decades is analyzed. Intrinsic safety factors linked directly to the pr…