Aeroelastic Tailoring Of Woven Cantilevered Glass-Epoxy Plate-Like Aircraft Wing

The application of uni-directional composites in aeroelastic tailoring has long been established due to their highly directional properties. However, the use of woven, bi-directional textile composite in this area is practically nil due to their lower strength and stiffness, although this class of material is generally cheaper and more conforming. Therefore, the current work presents a new prospect for this type of material in the aeroelastic tailoring of aircraft wings. The aeroelastic flutter and divergence behaviour of rectangular, woven glass/epoxy cantilevered plates with varying amount of bending and torsion stiffness coupling is investigated in subsonic flow. To do so, a range of tailored plate configurations with various stacking sequence having 6-plies thickness were considered. The ply orientation was varied from -450 to 450 to provide the widest range of negative and positive bend-twist coupling. Test plates without stiffness coupling were first constructed and subjected to static and dynamic testing in order to characterize the elastic and dynamic behaviour of the plate. Secondly, tailored configurations with varying stiffness coupling were fabricated and tested for flutter in wind tunnel tests. Numerical analyses were also conducted using MSc.Nastran structural analysis in conjunction with ZAERO’s flutter program to verify the mechanical and dynamic properties as well as predict the occurrence of flutter and divergence. Results from the extensive experimental and computational works had successfully shown that flutter speed can be optimized by tailoring the woven composite laminates. It was found that the torsional stiffness and bend-twist coupling play a major role in the aeroelastic behaviour of the woven laminate as compared to the bending stiffness. The bend-twist flutter that occurred was dominated by the torsion mode, thus explained the significant effect it has on the flutter speed. The numerical calculations predicted a 37% improvement whereas the experimental results are more understated at 29%. This improvement is remarkable considering that the configurations are symmetric. Both agreed well in terms of the optimized configuration that gave the maximum flutter speed. The flutter frequency and flutter mode shape was shown to be highly dependent on the coupled structural modes. In addition, divergence occurred when the plate-like wing is swept forward

Subsonic Aeroelastic Analysis of a Thin Flat Plate

The interaction between an aircraft structure and the airflow surrounding it has been known to severely affect the stability, performance and manoeuvrability of the aircraft. These interactions form the heart of aero elasticity, a field that comprises all types of aeroelastic phenomena. In this work, a parametric aeroelastic analysis of a thin flat plate clamped at the leading edge and exposed to subsonic airflow was conducted. The aeroelastic effects predicted to occur was flutter, a type of self-excited oscillation. The analysis was simulated using ZAERO, a panel code aeroelastic program, which requires free vibration input, obtained using MSC-NASTRAN, a finite element code. The flutter equation was obtained using Newton's Law of Motion to model the plate while the airflow was modeled using the Small Disturbance Unsteady Aerodynamic Theory. Free vibration results and flutter results obtained were validated against published works found in reference [8, 60 and 61]. The important parameters studied were the aspect ratio and the mass -ratio of the plate. The effect of the number of free vibration modes employed in the analysis was also tested. From the results, it was shown that the flutter velocity decreased as the mass ratio and aspect ratio were increased. The flutter frequency also decreased with higher mass ratio and at large aspect ratio. The use of a higher number of modes in the flutter analysis was found to increase the accuracy of the flutter

Honeycomb composite structures of aluminum: aerospace applications

A honeycomb composite structure is usually composed of a lightweight hexagonal core sandwiched between two thin face sheets that are adhesively joined. Both the core and the face sheets can be combinations of many types of materials depending on the application. In this article, an overview of the design and manufacturing process of aluminum honeycomb composite structures particularly for aerospace application is presented. Aluminum honeycomb composite structures are lightweight constructions with high specific strength and stiffness that are applied mainly in the aerospace industry. An aluminum honeycomb panel is typically made up of the secondary structural components and interiors of an aircraft such as the wing skin, trailing edge, control surface, flooring, partitions, aircraft galleys, and overhead bins, to name a few. Other applications are in the spacecraft, helicopter, missile, and satellite. Owing to its honeycomb design peculiar to the hexagonal beehives, it can reach more than 30 times higher in stiffness and 10 times higher in flexural strength compared to its solid counterpart of the same weight. The mechanical properties of the honeycomb composite structure hinge on the materials of the core and face sheets, the core geometries, and the thickness of the face sheets. Designed for superior flexural and shear loading, the selection of the optimal honeycomb design will depend on the application requirements. The principal design criterion of a sandwich structure in aerospace applications is weight saving, and there is a trade-off between performance and cost. In terms of manufacturing of the honeycomb composite sandwich structure, the two main processes are the expansion process commonly used for low-density cores and the corrugation process for higher density cores

Microstructural characterization of fly ash particulate reinforced AA6063 aluminium alloy for aerospace applications

Aluminium-fly ash (FA) particulate reinforced composites (AA6063-FA) have been used in automotive and aerospace industries because of their low density and good mechanical properties. Three different weight fraction of FA: 2%, 4% and 6% are added to AA6063 alloy using compocasting method. The effect of FA particulates on microstructure, density and compression strength of AA6063- FA composites are investigated. Field Emission Scanning Electron Microscope (FESEM) micrographs reveal that the FA particulates are uniformly distributed in AA6063 alloy. The results also show that density, compression strength and microstructure of the AA6063-FA composites are significantly influenced by the FA amount. The increase in the weight fraction of FA will improve the microstructure and enhance the compression strength. The density of AA6063-FA composites decreases as the incorporation of FA increases

The influence of fly ash on the microstructure and mechanical properties AA6063 alloy using compocasting technique

Fly ash (FA) has collected attention as a possible reinforcement material for aluminium matrix composites (AMCs) to improve the properties and decrease the production cost. In this study, AA6063 alloy was reinforced with FA particles by compocasting technique. The experiments were conducted by varying weight percentage of FA (0 to 12 wt.% in steps of 2%). The FA particles were incorporated into semisolid state of AA6063 alloy melt. The microstructure of aluminum-FA particulate composite (AA6063-FA) prepared with the homogenous distribution of FA was analyzed using X-ray Diffraction (XRD), Energy Dispersive X-ray spectroscopy analysis, Variable pressure scanning electron microscope (VPSEM) and Field emission scanning microscope (FESEM). The mechanical and thermal properties of the composites were determined with a tensile, compressive and thermal expansion tests. The experimental results indicated that the microstructure, mechanical and thermal properties of AA6063-FA composites were observably affected by increasing FA content. The fracture surface was observed to be different in the failure mechanism

Morphological, Mechanical, and Physical Properties of Four Bamboo Species

Bamboo among other plants has unique properties and massive variety. The properties of bamboo species vary between species and along their culms. The aim of this study was to investigate the characteristics of four bamboo species: Dendrocalamus pendulus (DP), Dendrocalamus asper (DA), Gigantochloa levis (GL), and Gigantochloa scortechinii (GS), and their three portions (bottom (B), middle (M), and top (T)). The number of fibre strands in vascular bundles and the single fibres extracted from every portion was studied. The distribution of fibres varied along the bamboo culms and between species. The DP species showed the highest water content and water absorption and the lowest mechanical properties. The DA species exhibited the best mechanical and physical properties. Moreover, the bottom portion of every species indicated the highest aspect ratio and tensile properties. The results indicated that before the application of bamboo culms in composite materials, the bamboo species should be characterized so that it can be utilised effectively as a renewable reinforcement in composites