In this study, halloysite nanotubes (HNT) were modified by: 3-glycidyloxypropy ltrimethoxysilane (GLYMO), 3-aminopropyltrimethoxysilane (APTES), and 2,2-Bis[4-(glycidyloxy) phenyl] propane (DGEBA), and incorporated in the epoxy resin matrix to enhance its mechanical properties. The HNT/epoxy nanocomposite materials were prepared by mixing different ratios of untreated/ treated HNT with neat epoxy resin. Characterization of untreated/treated HNT was performed by Fourier-transformation infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). The quantity of grafted molecules and thermal stability of newly synthesized materials were determined by thermogravimetric (TG) and derivative thermogravimetric (DTG) analysis. Tensile properties of newly synthesized materials were compared, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis of the fracture surfaces were performed. Incorporation of APTES modified HNT (HNTAPT) and twostep modification APTES followed by DGEBA (HNTAPTDG) has increased the tensile strength of the nanocomposite materials up to 72% and 61%, and strain at break up to 1082% and 1216%, respectively, compared to neat epoxy. It was concluded that the modification of HNT contributed to the enhancement of the dispersion and the cross-linking in the epoxy resin matrix.
Purpose This paper aims to present the methodology to determine Archard’s wear coefficient. By applying this coefficient into the numerical simulation of wear, it is possible to predict wear without long lasting and usually expensive experiments. Design/methodology/approach To determine necessary particles of Archard’s equation and calculate wear coefficient K, an experimental investigation is proposed. Afterwards, the wear simulation is executed in FEM software ANSYS 18.1. Analytical method is offered to determine worn volume for cylinder-in-cylinder contact, based on “inclination” of inner cylinder. Findings Comparing the value of Archard’s coefficient obtained by this experimental investigation with the values from the literature for the similar materials, high correlation is noted. Furthermore, numerically calculated contact pressure is confirmed with analytical method. Trend of pressure decrease due to wearing process, as well as due to increase of contact surface is observed. Practical implications Since the prediction of the wear is closely related to the life cycle assessment of bearings, and the machines in general, it has significant practical importance for designers. Originality/value Determination of Archard’s coefficient is usually performed by conventional pin-on-disk tribometers. This methodology offers a different approach for the determination of Archard’s wear coefficient for cylinder-in-cylinder contact, which is convenient for shaft-sliding bearing contact.
Composite films having the UV cured Bis-GMA (Bisphenol A glycidylmethacrylate)/TEGDMA (triethylene glycol dimethacrylate) as a matrix and the ferrous oxide doped alumina (Al 2 O 3 Fe) based particles were prepared and subjected to cavitation. In order to improve the mechanical and adhesion properties of composites, four different surface modifications of filler particles were performed: 3-methacryloxypropyltrimethoxysilane (MEMO), vinyltris(2-methoxyethoxy)silane (VTMOEO), (3-aminopropyl)trimethoxysilane (APTMS) and biodiesel (BD). Composite films were made with 0.5, 1.5, and 3 wt.% of ferrous oxide doped alumina particles with each of the mentioned surface modifications. Composite films were prepared on brass substrates and exposed to cavitation erosion. The erosion was monitored using the mass loss while image analysis was used to observe surface defects. The composite film reinforced with Al 2 O 3 Fe having VTMOEO as a surface modifier was the most resistant one in terms of mass loss, as well as the level of surface destruction. Results were compared to the same polymer matrix film and composite films prepared with fillers without surface modifications revealing that all composites with surface modified fillers exhibited some improvement in resistance to cavitation.
Chitosan based films have found an increasing implementation in variety of topics among which as drug delivery carriers, in packaging industry and as water puritication filters. Therefore, in order to achieve mechanical integrity of such films while preserving processability and biocompatibility, chitosan based films are fabricated in forms of blends with polyethylene oxide (PEO). Nanoindentation study is undertaken in order to investigate nanomechanical properties and surface morphology of chitosan films in blends with various content of PEO. Results of differential scanning calorimetry, water uptake and nanoindentation revealed that films with 80/20 blend ratio of chitosan/PEO showed the optimal values of reduced modulus and hardness. It appears that the incorporation of synthetic PEO in chitosan films could lower the manufacturing cost while preserving the mechanical integrity of the films. [Projekat Ministarstva nauke Republike Srbije, br. EUREKA E!5851
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