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Selected Methods of Modifying the Surface Layer of a Carbon Composite

Kłonica Mariusz, Kubit Andrzej, Perłowski Ryszard, Bielawski Radosław, Woś Sławomir

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 1

270--277

EN

This article presents the results of a comparative study on the modification of the surface layer of carbon composites. Fibre-reinforced polymer (FRP) composite materials are heterogeneous and anisotropic materials, characterised by high strength, low density, corrosion resistance along with ease of processing and moulding, and are increasingly replacing metal alloys. They are widely used in aviation, automotive and transport applications. One example of a modern composite is carbon fibre-reinforced polymer (CFRP). This study presents the influence of selected modifications of the surface layer of a CFRP composite on the values of free surface energy (SFE) and surface topography. The resulting SFE values were analysed together with the contribution of the polar SFE and dispersive SFE components. The article also presents the test results related to selected 3D surface roughness parameters and includes photographs of the test specimens after surface layer modification. The results were statistically processed in compliance with good research practice.

2

Experimental research on the influence of structural modifications of adherends on the load-bearing capacity of lap joints of S235JR steel sheets

Zielecki Władysław, Łabno Katarzyna, Perłowski Ryszard, Bąk Łukasz, Katrňák Tomáš

Advances in Mechanical and Materials Engineering

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2023

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Vol. 40, nr 1

5--13

EN

The paper presents the results of the research determining the impact of structural modifications of adherends on the load capacity of the joints determined in the static shear test. Tests of adhesive lap joints of S235JR steel sheets bonded with Araldite 2014-2 epoxy adhesive are described. The influence of technologically simple structural modifications was investigated; it consisted in making notches and holes at the leading edge of the adherends. These modifications were aimed at bringing about local flexibility of the joint in the sensitive area of stress concentration. Based on experimental studies, it was shown that there is a possibility of increasing the load-bearing capacity of the joint due to the applied modifications; in the most favorable variant, an increase in the load-bearing capacity by 15.9% compared to the base variant was demonstrated. The tests confirmed that the notches filled with the adhesive in the front part of the adherends can significantly improve the strength properties of joint, while the considered modifications in the form of holes do not have a significant impact on the properties of the adherends.

PL

W artykule przedstawiono wyniki badań określających wpływ modyfikacji konstrukcyjnych elementów klejonych na nośność złączy wyznaczoną w statycznej próbie ścinania. Opisano badania połączeń klejowych zakładkowych blach stalowych S235JR sklejonych klejem epoksydowym Araldite 2014-2. Zbadano wpływ prostych technologicznie modyfikacji konstrukcyjnych, polegających na wykonaniu nacięć i otworów na krawędzi natarcia elementów klejonych. Modyfikacje te miały na celu doprowadzenie do miejscowego uelastycznienia połączenia we wrażliwym obszarze koncentracji naprężeń. Na podstawie badań eksperymentalnych wykazano, że istnieje możliwość zwiększenia nośności złącza dzięki zastosowanym modyfikacjom. W najkorzystniejszym wariancie zaobserwowano wzrost nośności o 15,9% w stosunku do wariantu niemodyfikowanego konstrukcyjnie. Badania potwierdziły, że wypełnione przez klej nacięcia w przedniej części elementów klejonych mogą znacząco poprawić właściwości wytrzymałościowe złącza, natomiast rozważane modyfikacje w postaci otworów nie mają istotnego wpływu na właściwości elementów klejonych.

3

Experimental Research of the Weakening of the Fuselage Skin by RFSSW Single Row Joints

Kubit Andrzej, Bucior Magdalena, Kluz Rafał, Bochnowski Wojciech, Perłowski Ryszard

Advances in Science and Technology. Research Journal

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2019

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Vol. 13, no 3

90--97

EN

The paper presents the results of experimental investigations, the aim of which was to determine the degree of weakening of skin sheet of the thin-walled structure through a single-row welded joints made by Refill Friction Stir Spot Welding (RFSSW) technology. At the beginning, a short metallographic analysis of the weld was carried out, defining the characteristic areas of the microstructure. Then, comparative tests were carried out on the thin-walled structure sample in the form of a single-row skin-stringer joint. The structures made with the discussed technology of welding were compared with the traditionally joined structure by riveting. It has been shown that in the case of the welded structure, the skin sheet is weakened by more than 6% to a lesser extent than in the case of riveted. However, it was shown that the cracking path in the tensiled welded sheet runs along an unpredictable path, deviating from the line marked by the welds’ row. While in the case of riveted joint the cracking propagation along the row of rivets was revealed. The analyzes of fracture surfaces for both cases using scanning electron microscopy were also undertaken, thus undertaking preliminary considerations on the mechanism of fracture.