Search results for "Elastic"
showing 10 items of 2162 documents
A methodology for the rapid characterization of Mode II delamination fatigue threshold in FRP composites
2019
Abstract A new methodology to measure the Mode II interlaminar fracture in fatigue for FRP composites is developed. The proposed methodology uses a Modified Transvers Crack Tensile (MTCT) specimen and is able to characterize the near threshold behavior in a robust, easier and significantly faster way than standard procedures. Analytical formulae, able to link the crack growth rate to the load or strain amplitudes, were found and verified, and their importance was explained, in particular, for what concerns the characterisation of the near threshold behavior. Experiments were performed both in load and strain control, while the delamination growth was monitored using different techniques inc…
Large deflection of magneto-electro-elastic laminated plates
2014
Abstract A model for the large deflection analysis of magneto-electro-elastic laminated plates is derived. The first order shear deformation theory and the von Karman stress function approach are employed. A set of resolving partial differential equations involving kinematical variables and the stress function is obtained as a consequence of the preliminary condensation of the electro-magnetic state to the plate kinematics. A closed form solution for simply-supported plates is presented. Numerical results are carried out for plates consisting of piezoelectric BaTiO 3 and piezomagnetic CoFe 2 O 4 layers. These results show the influence of large deflections on the plate response and could be…
Fracture Toughness of Hydrothermally Aged Epoxy Systems with Different Crosslink Density
2015
Abstract The present work investigates the fracture toughness behaviour of Single Edge Notched Bending (SENB) samples of epoxy systems subject to water uptake aging. Two epoxy systems with a significantly different Glass Transition Temperature, T g , are in particular considered: a typical commercial non-aeronautical grade resin matrix for composite applications, reaching a T g of 90 °C, and a DGEBA+DDS epoxy system achieving a T g of 230 °C.The materials have been conditioned by hydrothermal aging in a thermal bath at the temperature of 50 °C. TransmissionPhotoelastic Stress Analysisis carried outon SENB samples during water aging, monitoring the presence and evolution of swelling stresses…
A theoretical approach to pneumatic muscle mechanics
2013
The mechanical response of pneumatic artificial muscles is analyzed assuming the inextensibility of the sheathing braids and taking into account the stress field inside the rubber bladder, which is regarded as a Mooney-Rivlin hyperelastic material. The end effects are simulated by heuristically profiling the meridian section. After estimating the constitutive parameters by traction tests on rubber specimens, the theoretical results are compared with experiments and a satisfactory accordance may be detected.
Rheological Response of Polyethylene/Clay Nanocomposites to Annealing Treatment
2007
The rheological response of a polyethylene/clay nanocomposite to annealing treatment under air and nitrogen atmospheres was studied. The treatment influences the rheology of the nanocomposite significantly. In particular, the viscosity and the non-Newtonian behavior dramatically increase with annealing time, and a liquid-like/solid-like transition is observed. The annealed samples were characterized by ATR-FT-IR spectrometry and it was shown that a silicate-rich layer is formed on the surface of the nanocomposite. This result was confirmed by TEM images of bulk and surface of annealed samples. It was demonstrated that the formation of this coating is the main cause of the change of rheologi…
Static and dynamic elasticity of some thermotropic liquid-crystalline copolyesters
1997
Two series of thermotropic liquid crystalline copolyesters were studied in static and dynamic tensile deformation. Static loading generally does not lead to any peculiar phenomena: the stress-strain diagrams are linear or convex, except one copolyester fibre, the stress-strain diagram of which is concave at high temperatures. On the contrary, in dynamic loading the elasticity modulus increased during deformation for all the samples investigated. So it can be assumed that formation of a more rigid and stable structure takes place due to the dynamic deformation.
Creep and damage accumulation in orthotropic composites under cyclic loading
1998
Experimental results and theoretical prediction of the response of glassfiber-reinforced polyester under quasi-static, static (creep), and cyclic (fatigue) loading are presented. The nonlinear strain component at static loading and the strain amplitude rate at cyclic off-axis loading of an orthotropic composite are shown to follow the associated flow rule with a single-parameter quadratic potential function. The influence of fatigue damage on deformation is considerable due to the reduction in the elastic modulus of the composite and is apparently negligible with respect to its effect on the parameters of the creep kernel.
Long-term ISO 23936-2 sweet oil ageing of HNBR
2021
Abstract A hydrogenated nitrile butadiene rubber (HNBR) compound is subjected to ageing in a simulated oil and gas environment in accordance with ISO 23936-2 standard at two elevated temperatures (130 °C and 150 °C) for a period of up to 9 months. Shore D hardness, thermal expansion, dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy, compression and compression set (CS) measurements are made before and after the chemical exposure. The hardness, modulus at short times, degree of relaxation and CS increases while the coefficient of thermal expansion in HNBR tends to decrease with ageing time and temperature. Temperature is shown to impose a greater effect on th…
Relating morphology to nanoscale mechanical properties: from crystalline to mesomorphic iPP
2005
Abstract A nanoindentation technique using an atomic force microscope (AFM) was applied to characterize the mechanical behaviour of several isotactic polypropylene (iPP) samples. The samples were solidified from the melt with a CCT (continuous cooling transformation) procedure spanning a wide range of cooling rates thanks to a fast quenching apparatus developed by the authors. The influence of instrumental parameters on the nanoscale mechanical properties (indentation depth, Young's modulus) shows that for modulus determination one has to rely on simpler methods of force curve analysis based on trace curve alone. Structure homogeneity up to the scale of macroscopic samples used to evaluate …
Processing, structure, property relationships and release kinetics of electrospun PLA/Carvacrol membranes
2018
Abstract In this work, polylactic acid (PLA) membranes at two different carvacrol (CRV) nominal concentration (i.e. 14 wt% and 28 wt%) were prepared via electrospinning technology. The membranes were characterized by scanning electron microscopy, ATR-FTIR and calorimetric measurements as well as tensile tests. Moreover, the release kinetics of CRV in phosphate buffered solution at 37 °C was monitored through UV–Vis measurements and the data were fitted with a power law model. Results indicated that the successful incorporation of CRV in the polymer matrix damaged the fibers morphology but increased all the mechanical parameters investigated (i.e. elastic modulus, tensile strength and elonga…