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Anti‑impact and vibration‑damping design of cork‑based sandwich structures for low‑speed aerial vehicles

Sheikhi Mohammad Rauf, Gürgen Selim, Altuntas Onder, Sofuoğlu Mehmet Alper

Archives of Civil and Mechanical Engineering

2023

Vol. 23, no. 2

art. no. e71, 2023

Nowadays, lightweight and eco-friendly composites with improved mechanical properties are highly interesting. Sandwich-structured composites are a type of high-performance structural composite that is lightweight with a high strength-to-weight ratio and excellent specifc energy absorption capabilities. In this study, cork-based sandwich structures resistant to impact and vibrations were designed and produced for the possibility of being used in the protective structures of low-speed aerial vehicles. To identify and match the best combination of different face sheets with a cork core, first, aramid fabric-reinforced polymer (AFRP), carbon fiber-reinforced polymer (CFRP), and glass fiber-reinforced polymer (GFRP) face-sheet composites were produced using the compression molding method (prepreg layup). Then, sandwich structures consisting of AFRP, CFRP, GFRP, and aluminum face sheets with a fixed core layer of cork were designed and assembled. Since the design goal of these structures is to use them in low-speed aerial vehicles, impact deceleration and vibration tests were applied to face sheets and sandwich structures individually, which are the most important factors involved in these structures during fight, particularly in rotary-wing drone applications. A low-energy drop-tower system was used for the calculation of deceleration results. Besides, the vibration properties of the structures were investigated using the modal analysis method and based on the natural frequency responses of the tested face sheets and sandwich structures, damping ratios and structural stiffness were measured. According to the results, compared to other face sheets, CFRP showed better resistance along with the cork core, when the structure was exposed to impact and vibration threats. This study provides useful information on cork core sandwich structures for academic and industrial researchers in choosing the right face sheet.

Proposal of welding methods in terms of the amount of oxygen

Węgrzyn T.

Archives of Materials Science and Engineering

2011

Vol. 47, nr 1

57-61

Purpose: Purpose of this paper is to remind proposals for welding processes classification in terms of oxygen in WMD (weld metal deposit), and confirmation of that concept after further 12 years of new research and results. Design/methodology/approach: Welds were obtained with various oxygen content. There were investigated properties of WMD, especially metallographic structure, toughness and fatigue strength of welds with various oxygen amount. The connection between the properties of welds with the content of oxygen in WMD were carried out. Findings: Demonstrated that oxygen content in WMD has an important influence on metallographic structure, especially on the percentage of acicular ferrite in weld. The preferred structure improves the mechanical properties of welded joints. Research limitations: The research results indicate that oxygen content in steel welds should be limited. Subsequent researchers could find more precisely the most beneficial oxygen amount in the welds in terms of the amount of acicular ferrite in welds. Practical limitations: To obtain welds with the best properties should be chosen suggested low-oxygen process. It is therefore suggestion to use much more basic electrodes than rutile for steel welding. Originality/value: Proposal of welding methods in terms of oxygen content in welds was given 12 years ago, however still it is not very popular. New researches and results could prove that it is very important and original proposal.