The aim of our research was to investigate the effect of a small nanocellulose (NC) addition on an improvement of the mechanical properties of epoxy composites. A procedure of chemical extraction from pressed lignin was used to obtain nanocellulose fibers. The presence of nanoparticles in the cellulose pulp was confirmed by FTIR/ATR spectra as well as measurement of nanocellulose particle size using a Zetasizer analyzer. Epoxy composites with NC contents from 0.5% to 1.5% w/w were prepared. The obtained composites were subjected to strength tests, such as impact strength (IS) and resistance to three-point bending with a determination of critical stress intensity factor (Kc). The impact strength of nanocellulose composites doubled in comparison to the unmodified epoxy resin (EP 0). Moreover, Kc was increased by approximately 50% and 70% for the 1.5 and 0.5% w/w NC, respectively. The maximum value of stress at break was achieved at 1% NC concentration in EP and it was 15% higher than that for unmodified epoxy resin. The highest value of destruction energy was characterized by the composition with 0.5% NC and corresponds to the increase of 102% in comparison with EP 0. Based on the analysis of the results it was noted that satisfactory improvement of the mechanical properties of the composite was achieved with a very small addition of nanofiller while other research indicates the need to add much more nanocellulose. It is also expected that this kind of use of raw materials will allow increasing the economic efficiency of the nanocomposite preparation process. Moreover, nanocomposites obtained in this way can be applied as elements of machines or as a modified epoxy matrix for sandwich composites, enabling production of the structure material with reduced weight but improved mechanical properties.
This paper reports the results of the effect of sea water, natural ageing, and cross-impact loading on flexural strength and residual flexural strength of epoxy laminates with glass woven fabrics and hybrid reinforcement with glass and carbon woven fabrics. The tests were conducted on samples with different fibre reinforcement both before and after low energy cross-impact loading. Carbon fabrics decreased residual strength of the composites.
The present work investigates the ablative and thermal properties of epoxy resins modified with silicon carbide (SiC) and tungsten carbide (WC). The properties of two epoxy resins (Epidian 52 cured with triethylenetetraamine and Epidian 112 cured with polyaminoamide) were investigated in this study. Statistical methods for planning experiments were used, and the effect of components on thermal protective properties of epoxy composites established. It was shown that the best thermal protective properties, i.e. the lowest temperature of the rear surface area and the lowest ablative weight loss (the highest thermal stability) were exhibited by the composite based on Epidian 112 containing 56% of silicon carbide SiC and 14% of tungsten carbide WC. A more stabilized ablative layer and limited erosion were obtained with higher SiC content. Moreover, the type of polymer matrix had the most significant effect on the value of the maximum temperature of the rear surface area.
BACKGROUND. Patients who undergo total hip arthroplasty (THA) find it difficult to return to work. OBJECTIVES. Analysis of factors influencing return to work after THA. Assessment of patients' quality of life and its impact on their attitude to work. MATERIAL AND METHODS. We studied patients operated on for degenerative hip disease at the Department of Orthopaedic Surgery of Medical Centre of Postgraduate Education in Otwock between 2007 and 2012. The total number of the patients was 400; however, we chose only those patients who were younger than 65 and still in employment. The study population consisted of 54 of these patients. The mean patient age was 55.89 (±7.424). There were 29 men (57.3%) and 25 women (46.3%). RESULTS. 32 patients (59.3%) returned to work. There was a statistically significant difference regarding the attitude to work and return to work. An overwhelming majority of the patients who returned to work--31 out of 32 (96.6%)--liked their jobs. The 12 patients (22.22%) who did not return to work declared their intention to apply for a disability pension. The patients who returned to work assessed their physical health as better than the patients who did not return to work. CONCLUSIONS. 1. 40.7% of patients after THA did not return to preoperative employment. The reasons for not returning were not medical, because elimination of pain and an increased range of motion made return to work possible. 2. The perception of the quality of physical and psychological health among patients with THA who returned to work was significantly better than among those who did not return.
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