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

LCO flutter of cantilevered woven glass/epoxy laminate in subsonic flow

The paper presents aeroelastic characteristics of a cantilevered composite wing, idealized as a composite flat plate laminate. The composite laminate was made from woven glass fibers with epoxy matrix. The elastic and dynamic properties of the laminate were determined experimentally for aeroelastic calculations. Aeroelastic wind tunnel testing of the laminate was performed and the result showed that flutter, a dynamic instability occurred. The cantilevered laminate also displayed limit cycle amplitude, post-flutter oscillation. The experimental flutter velocity and frequency were verified by our computational analysis

Flutter analysis of a hybrid plate-like fiber-reinforced composite wing

The aeroelastic flutter of a laminated hybrid composite wing was investigated. The composite wing was modelled as composite plates and the aeroelastic analysis has been carried out in the frequency-domain. Pre-determined fiber orientation of a 3-layers carbon/epoxy and glass/epoxy laminated plate has been employed with various aspect ratios. The modal approach and the Doublet-lattice Method (DLM) have been used herein to calculate the normal modes and the unsteady aerodynamics of the plate. The structural and aerodynamic models were connected using surface splines and the flutter speed has been calculated using the p-k method that provides the eigenvalues at different air densities and airstream velocities. The study showed that it is imperative that the carbon/epoxy should be employed in the outermost layers in order to improve the flutter speed and flutter frequency

Preliminary investigation on experimental modal analysis of high aspect ratio rectangular wing model

Procedure of conducting an experimental modal analysis (EMA) of roving hammer test for high aspect ratio (HAR) wing containing geometric nonlinearities is presented along with consideration of various tip store sizes. Two sets of test setups of vertical and horizontal arrangements have been considered, which respectively demonstrates the undeformed and deformed cases. Modal properties in terms of natural frequency and mode shape were experimentally measured using the LMS Test.Lab package and the results were then compared between the undeformed and its corresponding deformed configuration. From the finding, it confirms that the chordwise and torsional modes of the undeformed configurations has respectively turned into chordwise-torsion and torsion-chordwise modes as they are in deformed configuration. Meanwhile, the impact related to bending modes is insignificant. Hence, this may result in inaccurate prediction if conventional aeroelastic solution is employed for HAR wing configuration

Tensile behaviour of unbalanced woven C-glass/epoxy composite laminated plate with and without circular cutouts

In present days experimental investigation for composites material has been a very important study to determine not only the materials properties but also the behaviour of the produced composite. For this study, an experimental investigation to determine the tensile behaviour and failure modes of unbalanced woven C-glass/epoxy composites laminated panels was performed. Series of coupon tests are carried out for the unbalanced C-glass/epoxy laminates according to ASTM 3039 to obtain their mechanical and strength properties which are then used to calculate the load-displacement curves, the ultimate load and the energy absorption capabilities for each coupon panel. Study conducted are by varying the cut-out sizes and varying the fibre angle orientations, it was discovered that cross ply laminates had the highest ultimate load and that increasing the cut-out size reduced the ultimate load of the panels. Visual inspections of the damage specimens using microscopic camera are also carried out for certain type of composite laminates to investigate the mode of failures. In general all of the samples exhibit almost similar types of failure modes such as fibre breakage, delamination, debonding and matrix cracking

Extraction and preparation of bamboo fibre-reinforced composites

Natural plant fibre composites have been developed for the production of a variety of industrial products, with benefits including biodegradability and environmental protection. Bamboo fibre materials have attracted broad attention as reinforcement polymer composites due to their environmental sustainability, mechanical properties, and recyclability, and they can be compared with glass fibres. This review classifies and describes the various procedures that have been developed to extract fibres from raw bamboo culm. There are three main types of procedures: mechanical, chemical and combined mechanical and chemical extraction. Composite preparation from extracted bamboo fibres and various thermal analysis methods are also classified and analysed. Many parameters affect the mechanical properties and composite characteristics of bamboo fibres and bamboo composites, including fibre extraction methods, fibre length, fibre size, resin application, temperature, moisture content and composite preparation techniques. Mechanical extraction methods are more eco-friendly than chemical methods, and steam explosion and chemical methods significantly affect the microstructure of bamboo fibres. The development of bamboo fibre-reinforced composites and interfacial adhesion fabrication techniques must consider the type of matrix, the microstructure of bamboo and fibre extraction methods

Improving the stiffness of multilayer 3D woven composites by the integration of shape memory alloys (SMAs) into structures

Shape memory alloys (SMAs) are capable of shape-retaining and stress generation when activated. SMA wires are embedded in laminated composites for improving the properties of the composites. Laminated composites have low through-the-thickness properties and poor delamination resistance. 3D composites are well known for having higher through-the-thickness properties. In 3D woven composites, a set of yarn is in through-the-thickness direction that improves through-the- thickness properties and provides resistance to delamination of layers. As in multilayer 3D woven structures, yarns are distributed from in-plane to through-the-thickness direction, so in-plane properties are reduced with the same number of yarns compared to 2D laminated composites. In this research, SMA wires are embedded into different types of 3D woven structures for utilising stress generation property of SMA wires for improving in-plane properties, specifically stiffness of the composites. Three types of 3D orthogonal interlocking composites: layer-to-layer, through-the-thickness, and modified multilayer interlock structures are fabricated with and without SMA wires. From the tensile test, results show that embedding SMA wires into structures significantly improves the stiffness of the structures due to the stress-induced martensite phase of SMA wire when subjected to load. When these SMA wires are activated, stresses are generated by SMA wires due to phase transformation from martensite to austenite that further gives remarkable higher values of stiffness. This results in a composite structure that has higher in-plane properties due to embedded SMA wire and through-the-thickness properties due to 3D structure of composite reinforcement. The interlocking pattern in the through-the-thickness direction of 3D structures was also found to have an effect on the extent of the improvement in stiffness

Critical speeds for carbon/epoxy composite rotors in spacecraft energy storage applications

A numerical investigation to optimize the carbon/epoxy multi layer composite rotor is performed for the spacecraft energy storage application. A high-speed double and triple layer rotor design is proposed and different composite materials are tested to achieve the most suitable recipe. First, analytical rotor evaluation was performed in order to establish a reliable numerical composite rotor model. Subsequently, finite element analysis is employed in order to optimize the double and triple layer composite rotors. Then, the modal analysis was carried out to determine the rotor natural frequencies. The rotor stress distributions and the rotor mode shapes show that a safe operational regime below 46, 000 rotations per minute is achievable

Condition Structural Index using Principal Component Analysis for undamaged, damage and repair conditions of carbon fiber-reinforced plastic laminate

This article deals with the data reduction technique using the principal component analysis applied to the carbon fiber–reinforced plastic panels for structural health monitoring approaches. Two carbon fiber–reinforced plastic panels subjected to damage and repair coincide with typical aircraft repair procedures found in the aircraft structural repair manual. The panels were simulated with 30 mm diameter of partial and full penetration damages using a diamond-coated router. The data (50 observations) were captured for the undamaged, damaged, and repaired conditions by placing lead zirconate titanate smart sensors at 100 mm across the damaged and repaired structures. A time-based data response was captured for post analysis during the interrogation on the structure at each condition. The raw data were captured in a Lamb waveform, and the interested features were extracted using Morlet wavelet analysis to evaluate the Condition Structural Index and Amplitude-Based Assessment for each condition retrieved from the Gaussian-like distribution. The results were evaluated using the principal component analysis technique in order to distinguish the characteristic of the undamaged, damaged, and repaired conditions. The results showed that in all cases considered, it was possible to distinguish the conditions of undamaged, damaged, and repaired states with promising accuracy and repeatability of the data