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The newly developed airplanes are using composite laminates to replace the metal alloys for different components, such as the fuselage and the wings. The major advantage of the composite materials is to reduce structural weight which results in reducing the fuel consumption. The aim of this project is to investigate the structural integrity of an a...
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Reducing noise in mobile applications such as cars, aircrafts and trains is a major challenge for today's engineers. In most cases, sound sources and sound radiating structures are locally separated. The airborne sound field is a result of the excitation and the transfer through the mechanical system. The resulting structure‐borne sound is propagat...
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Citations
... The application of sandwich-structured composites has significantly increased due to their suitability in developing lightweight structures with high mechanical performance and they have become the first choice in various applications, especially in the structural field [3,4]. Sandwichstructured composites have begun to be widely used in vast areas, ranging from satellites [5] and aircraft wings [6], as well as marine [7], transportation [8], sport [9], and drone or military applications [1]. Using sandwich-structured composites in transportation applications results in a lighter vehicle with better fuel efficiency and payload capacity [10,11]. ...
Cellulose is classified as one of the most abundant biopolymers in nature. Its excellent properties have gained a lot of interest as an alternative material for synthetic polymers. Nowadays, cellulose can be processed into numerous derivative products, such as microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC). MCC and NCC have demonstrated outstanding mechanical properties owing to their high degree of crystallinity. One of the promising applications of MCC and NCC is high-performance paper. It can be utilized as a substitute for the aramid paper that has been commercially used as a honeycomb core material for sandwich-structured composites. In this study, MCC and NCC were prepared by extracting cellulose from the Cladophora algae resource. MCC and NCC possessed different characteristics because of their distinct morphologies. Furthermore, MCC and NCC were formed into a paper at various grammages and then impregnated with epoxy resin. The effect of paper grammage and epoxy resin impregnation on the mechanical properties of both materials was studied. Then, MCC and NCC paper was prepared as a raw material for honeycomb core applications. The results showed that epoxy-impregnated MCC paper outperformed epoxy-impregnated NCC paper with a compression strength of 0.72 MPa. The interesting result from this study is that the compression strength of the MCC-based honeycomb core was comparable to the commercial ones despite being made of a natural resource, which is sustainable and renewable. Therefore, cellulose-based paper is promising to be used for honeycomb core applications in sandwich-structured composites.
... Stringer stiffened composite panels consisting of longitudinal or transversal stiffeners and skin have been widely employed in aerospace industry, owing to their remarkable specific modulus and strength. Specifically, hat-stiffened composites featuring outstanding structural stability and efficiency have been extensively investigated in aircraft fuselages [1][2][3][4][5]. Accordingly, hat-shaped stringers and panel can be bonded together by secondary bonding, co-bonding and co-curing process in a hat-stiffened composite panel [6,7]. ...
Integrated and automated manufacturing processes of advanced composites have attracted extensive attention, aiming at the improvement of mechanical performance and cost efficiency of composites. This experimental study investigated the feasibility of a manufacturing process for co-cured integral hat-stiffened panels based on automated fiber placement. To achieve desirable manufacturing quality and simplify manufacturing process, a novel flexible inner mold was designed for the enclosed cavity between stringers and skin, which was suitable for curved and large hat-stiffened panels. Influences of flexible mold and processing parameters on dimensional accuracy were studied by both finite element analysis and experimental methods. Moreover, fiber distribution around the transition region between skin and stringer were obtained through microscopy observation. With the optimum inner mold and layup processing parameters, hat-stiffened composites can be manufactured integrally with improved surface quality and geometric accuracy, based on co-curing process and automated fiber placement.
The design process for stiffened lightweight structures faces many challenges. Current design goals, especially in the aircraft industry, demand significant decrease in structural weight while keeping development and manufacturing costs low. Therefore, more complex design choices are investigated and show promising potential. The resulting increase in computational effort presents a remaining challenge. A novel approach for the design of stiffened lightweight structures, that enables strategic application of individualization and therefore allocates computational effort to areas of a structure where high benefits can be expected, is presented. Starting from a structure with common parts, the concept of individualization, i.e. adapting the design to local loads, is applied iteratively to selected parts of the structure. The methodology of strategic individualization is explained in detail before being applied to an example structure. This application shows the general capability of the methodology to design lightweight structures with less computational effort compared to a conventional approach.
