Gábor Szebényi

Effect of Epoxidized Soybean Oil on Curing, Rheological, Mechanical and Thermal Properties of Aromatic and Aliphatic Epoxy Resins

In order to facilitate the application of bio-based resins in more demanding advanced sectors as electrical and aeronautical industry, a systematic study was carried out to characterize the effect of epoxidized soybean oil (ESO), one of the most commonly used bio-based resins, on curing and rheological behavior, glass transition temperature, mechanical and thermal properties in various epoxy resin systems. Besides the conventional, widely investigated aromatic diglycidylether of bisphenol-A (DGEBA) resin, a glycerol- and a pentaerythritol-based aliphatic resin was chosen as base resin, whose synthesis is feasible from renewable materials as well, in the end leading to full replacement of mineral oil based resins by renewable sourced ones. In the hybrid resin system the ESO content was systematically increased from 0 to 100 mass%. The results indicate that in the case of the DGEBA containing hybrid systems the overall performance deteriorates with increasing ESO-content, while in the case of the aliphatic resins the glass transition temperature increases.

Preparation of MWCNT/Carbon Fabric Reinforced Hybrid Nanocomposite and Examination of its Mechanical Properties

In our work we have prepared carbon fiber/epoxy composite and carbon fiber/carbon nanotube/epoxy hybrid nanocomposite laminates by hand laminating assisted by vacuumbag technology. During the production of the specimens we have encountered the viscosity increasing effect of nanotube filling, which we characterized by a viscosity test. The results of the test showed, that in the lowest shear rate range carbon nanotube filling can cause an increase of viscosity by three orders of magnitude, but also at higher shear rates the viscosity of the nanotube filled epoxy resin was ten times the viscosity of the unfilled resin. Mechanical properties of the composite and hybrid composite have been compared by tensile, bending and interlaminar shear tests. During the tensile tests AE signals have also been recorded. The fracture surfaces have been examined by SEM micrographs. The nanotube filling has decreased the tensile strength and the modulus of elasticity by 7-8 percent presumably indirectly, the bending properties didn’t change noticeably, but the interlaminar shear strength of the composite has increased by 15 percent thanks to nanotube filling of the matrix. The decrease of the delamination inclination of the hybrid composite has been affirmed both by the AE and SEM results.

The Effect of Electron Irradiation on the Mechanical Properties of MWCNT/Carbon Fiber Reinforced Hybrid Nanocomposites

In our work carbon fiber/epoxy composite and multiwalled carbon nanotube/carbon fiber/epoxy hybrid nanocomposite laminates have been prepared by resin transfer moulding (RTM) technology. The specimens have been irradiated using a high energy electron gun with multiple doses. The effect of the electron irradiation has been characterized using three point bending, interlaminar shear and instrumented falling weight impact tests.

Effect of an ionic liquid on the flexural and fracture mechanical properties of EP/MWCNT nanocomposites

The improvement of interfacial adhesion between multiwalled carbon nanotubes (MWCNTs) and epoxy resin (EP) was investigated in nanocomposites with the addition of an ionic liquid (IL, 1-Ethyl-3-methyl imidazolium tetrafluoroborate - EMIM BF4) as interfacial adhesion promoter. MWCNT (0, 0.3 and 0.5 weight%) was dispersed in EP through diluting an MWCNT-rich masterbatch prepared in presence and absence of IL. Three point bending and compact tension (CT) fracture mechanical tests were performed on specimens with different MWCNT contents with and without IL surfactant. IL addition resulted in easier dispersion of MWCNT in the EP masterbatch. With the addition of the IL the three point bending strength, the bending modulus of elasticity and the critical force required for crack propagation have increased significantly at the optimal, 0.3 weight% MWCNT content. Scanning electron microscopic (SEM) investigation of the fracture surfaces of the CT specimens revealed that incorporation of MWCNTs and its IL-assisted dispersion produced rougher surfaces suggesting higher fracture toughness than the reference EP.

An elastic phenomenological material law for textile composites and it's fitting to experimental data

Constitutive description of deformations in technical textiles mostly requires some highly nonlinear material law because of the interaction between the orthotropic yarns and the effect of the matrix. Phenomenological models aim to capture the overall (macro level) behaviour needed in engineering applications. This paper introduces a new, two-dimensional phenomenological model for technical textiles, accompanied by a data acquiring strategy to determine the material parameters involved in the model. It handles the nonlinear stress–strain relation observed in uniaxial tests and takes the interactions in the two, orthogonal directions into account. As we aim to introduce a solution applicable at the service level of the loads, our model is inherently elastic, no time dependent or plastic behaviour are introduced and no cyclic loading is taken into consideration. The model can be solidly fit to the measured data.