Search results for "Elastic Modulu"
showing 10 items of 189 documents
Mechanical and thermomechanical properties of radiation modified poly(ethylene-octene)/Ni-Zn ferrite nanocomposites
2013
Poly(ethylene-1-octene) copolymer (POE) composites filled with nickel-zinc ferrite nanoparticles have been modified by exposure to an electron beam at doses up to 500 kGy. The influence of radiation dose and ferrite content on mechanical properties has been investigated. Thermomechanical properties – thermorelaxation stresses formed in thermal heating and thermo residual stresses resulting in the process of full setting and cooling of materials have been investigated for radiation cross-linked oriented (extended up to 100%) composite samples. Increase of concentration of ferrite particles and increase of radiation dose affects a notable increase of elastic modulus and reduces the deformabil…
Nanoindentation response analysis of Cu-rich carbon–copper composite films deposited by PVD technique
2015
Abstract The micromechanical properties of sputter deposited amorphous carbon–copper (a-C/Cu) composite films with different carbon content (6.8–19.8 at.%) were investigated. Atomic force and electron microscopy studies confirmed that the a-C/Cu films have a two-phase microstructure of amorphous sp 2 /sp 3 -bonded carbon as a composite matrix with embedded copper nanocrystallites encapsulated in a graphene shell. Load–displacement curves obtained in nanoindentation experiments followed Meyer's law with the exponent varying slightly within the interval 2.0–2.2 depending on the penetration depth and carbon content. The reverse indentation size effect was observed which was most likely the res…
Mechanical properties of the nanometer scale pre-crystalline order of a poly (ethylene terepthalate) / poly (ethylene naphthalene) blend
2006
A previous study carried out on PET has shown that this polymer undergoes a continuous structural modification over a wide cooling rate interval when solidified from the melt[1] assuming a semi-crystalline structure below 2 K s 1 and a completely amorphous one above 100 K s 1. Most important was the existence of a state of intermediate order between the above cooling rates which was evidenced by the absence of crystalline reflections in the WAXS patterns and the occurrence of SAXS maxima[2] and exothermic peak areas (DSC) in the cooling rate range above 2 K s 1. Microhardness (MH) measurements revealed that this phase affects the mechanical properties[3] plausible if one thinks of crystalli…
X-ray micro-tomography based FEM modelling of hygroexpansion in PLA composites reinforced with birch pulp fibres
2017
This article presents a microscale modelling approach coupled with X-ray computed micro-tomography for the evaluation of material properties of polylactic acid (PLA) reinforced by birch pulp fibers under the effect of moisture. The results in terms of elastic moduli and hygroexpansion deformation were found in good agreement with the measurements taken at different levels of water uptake.
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…
Redox-Responsive and Thermoresponsive Supramolecular Nanosheet Gels with High Young's Moduli
2018
Supramolecular gels made from 2D building blocks are emerging as one of the novel multifunctional soft materials for various applications. This study reports on a class of supramolecular nanosheet gels formed through a reversible self-assembly process involving both intramolecular folding and intermolecular self-assembly of poly[oligo(ethylene glycol)-co-(phenyl-capped bithiophenes)]. Such hierarchical self-assembled structure allows the gels to switch between sol and gel states under either redox or thermostimulus. Moreover, the gels illustrate high Young's moduli, compared to their controls that are made from the same oligo(ethylene glycol) and phenyl-capped bithiophenes blocks but have h…