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EN
This article describes the results of tribological research into epoxy-based composites reinforced with carbon fiber. The composites were subjected to accelerated tests simulating asemi-annual influence of environmental conditions of an elevated temperature, precipitation in combination with an influence of UV-A radiation of 0.83 W/m2 as well as cyclic thermal shocks causing a leap temperature difference of 116.5°C. The process of friction was conducted in conditions of dry friction and wet friction in the presence of water. The authors found apositive influence of a two-month impact of environmental conditions upon increasing wear resistance. They found a reduction in weight in conditions of friction with water. At the same time, a reliability analysis for the same boundary conditions showed an increased risk of critical composite damage. The article indicates areas of safe exploitation of composites and areas of the necessity of withdrawing composites from further exploitation under the assumed environmental and tribological loads.
EN
In the present study, the evolution of different failure mechanisms in carbon fiber reinforced polymer composites is being investigated using acoustic emission technique, unsupervised clustering technique and improved b-value analysis. The experimental part involved the realization of tensile tests of different materials, namely samples with [0/90]2S uniaxial layer configuration and [0/90]2S twill fabric samples. Both types of tests were monitored using one wideband acoustic emission sensor, while the tensile tests of twill fabric samples were additionally supplemented with resonant acoustic emission sensor to perform a comparative analysis between datasets from resonant/wideband acoustic emission sensor. The comparative study itself was preceded by the failure mechanisms characterization process, which has been performed on the tensile test dataset of [0/90]2S layer configuration with the contribution of clustering technique. The subsequent analysis of the twill fabric resonant/wideband acoustic emission sensor datasets included the improved b-value technique, which relates the magnitude of fracture with the slope of the amplitude distribution. The presented results, especially in terms of the improved b-value technique applied to individual clusters, show enhanced ability to assess in more detail the actual structural integrity depending on the applied load.
EN
The paper presents a study on influence of different fabric weave and fabric orientation on strength properties of fiber reinforced polymer composites. The research concerns materials used in a new type of rotorcraft. Four series of laminates were fabricated with hand forming, using the MGS L285/H285 epoxy resin. Triple-kind experiments were performed: the Shore hardness measurements, tensile strength testing and fractographic analysis. The specimens of different series shown various strength and stiffness characteristics, depending on the type of weave and fabric layup. Three different failure schemes were observed. The Poisson coefficient was different among series, as well, but no understandable link to specimen morphology could be found so far. Fractographic observations suggested intralaminar delamination.
PL
Celem niniejszego artykułu jest przedstawienie najważniejszych informacji dotyczących kompozytów typu CFRP i przykładów ich zastosowania w budowie pojazdów szynowych. W pierwszej części artykułu przedstawiono podstawowe cechy charakterystyczne kompozytów typu CFRP, a także zaprezentowano porównanie ich właściwości z właściwościami konwencjonalnych materiałów konstrukcyjnych. Następnie omówiono przykłady wykorzystania kompozytów z tej grupy w budowie elementów konstrukcyjnych pojazdów szynowych. Ostatnią część artykułu stanowi analiza motywacji, które przemawiają za wprowadzeniem tego rodzaju kompozytów do inżynierskiej praktyki kolejowej.
EN
The aim of this article is to provide crucial information on CFRP composites and examples of their use in rail vehicle construction. The first part outlines the key characteristics of CFRP composites and compares their properties with conventional structural materials. Implementation examples of this group of composites for structural components of rail vehicles are discussed further. The final section of the article analyses the reasons for introducing composites of this type into the engineering practice of railways.
PL
W pracy przedstawiono analizę wybranych parametrów zmiennych na skuteczność wzmocnienia zginanych elementów żelbetowych przy użyciu naprężonych materiałów kompozytowych FRP. Dyskusją objęto obszerną bazę wyników badań doświadczalnych, na podstawie której omówiono wpływ stopnia istniejącego zbrojenia stalowego, stopnia zbrojenia kompozytowego oraz poziomu wstępnego naciągu kompozytu na stopień wzmocnienia elementów. Aby uniknąć wpływu zróżnicowania parametrów zmiennych, wyniki podzielono na grupy ze względu na sposób zniszczenia oraz poziom wstępnych naprężeń kompozytu.
EN
The paper presents an analysis of selected variable parameters on strengthening effectiveness of reinforced concrete members under flexure using pretension FRP materials. A discussion contains an extensive database of experimental test results, based on which the influence of the existing steel reinforcement ratio, the FRP reinforcement ratio and the pretensioning FRP strain on the strengthening efficiency. In order to avoid the influence of variable parameters, test results were divided into groups differ in a failure mode and a level of initial FRP prestressing.
EN
A new approach based on measurements of a local nonlinear response of the laminate is suggested and applied to characterizing contaminations of adhesive bonding in carbon fibre reinforced polymer (CFRP). It is shown that a contaminated boundary layer of the adhesive contributes to an overall nonlinear response of the laminate that enables to recognise the difference in bonding quality caused by various types and levels of contaminations.
PL
W artykule, w celu scharakteryzowania zanieczyszczeń połączeń klejonych polimerów wzmocnionych włóknem węglowym (CFRP), zaproponowano i następnie zastosowano nowe podejście oparte na pomiarach lokalnej nieliniowej odpowiedzi laminatu. Pokazano, że zanieczyszczona warstwa graniczna kleju przyczynia się do ogólnej nieliniowej odpowiedzi laminatu, która umożliwia rozpoznanie różnicy w jakości wiązania spowodowanej różnymi typami i poziomami zanieczyszczeń.
EN
Presently a lot of designs of light armours are based mainly on the multilayer composite materials. Thanks to these materials it was possible to achieve highest levels of ballistic resistance of specific armour at limited weight. The weight (area density) and the performance have direct influence on the value of combat ability of equipment and soldiers. Carbon fibers are basic types of reinforcement used in composites. They have many technical applications including light ballistic covers where they are mostly used as multi-layer composite materials constituting a structure made of several interconnected layers or many layers of carbon fibers, or in combination with other materials. Light ballistic covers have usually thickness of several to 10-20 mm and potential defects occurring in them have thermo-physical properties definitely different than materials they are made of so the non-destructive tests using thermography methods may be effective in detecting these defects. The main methods of active thermographic tests are as follows [1, 2]: - Pulsed Thermography – PT, - Step Heating Thermography – SHT, - Lock-in Thermography – LT, - Vibrothermography – VT. In the paper an application of Step Heating Thermography and Vibrothermography to detection of delaminating area of CFRP composites after mechanical impacts is presented.
PL
Opisano własną propozycję zależności określającej nośność przekroju poprzecznego elementów ściskanych wzmacnianych zewnętrznym zbrojeniem kompozytowym CFRP. Oceniono zaproponowany model analityczny w świetle wyników badań własnych i obcych.
EN
The own method of calculation of cross-section load-bearing capacity of compressed members strengthened with external composite CFRP reinforcement is described. Proposing analytical model was verified with own and the other researchers experimental studies.
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