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

Temperature and strain feedback control for shape memory alloy actuated composite plate

There are several input variables that can be used to control the deflection of a shape memory alloy (SMA) composite system such as the resistance or temperature of the SMA actuator and position or strain of the composite plate. It is common to control the actuator directly, however SMA is nonlinear and it exhibits hysteresis which may result in inaccurate control of the plate’s deflection. Thus controlling the plate’s deflection may be more effective by using input measurement from the composite plate. The aim of this study is to propose the optimal feedback variable deflection control of a fiberglass composite plate system using SMA actuators. Two types of variables were investigated which were temperature of the SMA actuator and strain of the composite plate. The feedback control system for SMA actuated composite plate was implemented with different types of sensors; thermocouple and strain gauge. When current is supplied to the SMA actuator, it will contract and produce a force that will deflect the composite plate. During this process, the SMA actuator’s temperature changes with the current supplied and the strain of the composite plate changes during deflection due to torsion and bending. Thus, it is proposed to use these variables as the input to the feedback of the smart composite plate system to control the movement of the plate. Using the adopted control technique of the experimental test bench presented here, the strain feedback system was more effective and energy efficient compared to the temperature feedback for the control of morphing composite plate

Aircraft pitch control tracking with sliding mode control

Sliding mode control (SMC) is one of the robust and nonlinear control methods. An aircraft flying at high angles of attack is considered nonlinear due to flow separations, which cause aerodynamic characteristics in the region to be nonlinear. This paper presents the comparative assessment for the flight control based on linear SMC and integral SMC implemented on the nonlinear longitudinal model of a fighter aircraft. The controller objective is to track the pitch angle and the pitch rate throughout the high angles of attack envelope. Numerical treatments are carried out on selected conditions and the controller performances are studied based on their transient responses. Obtained results show that both SMCs are applicable for high angles of attack

Active control of strain in a composite plate using shape memory alloy actuators

The present study aims to design an experimental test bench to analyze and control a smart structure system composed of a woven fiberglass laminate plate with shape memory alloy (SMA) actuators instilled on the surface. The aim of this design is to accurately augment the strain of the composite plate. Finite element analysis was employed to model the composite structure and determine the placement of the SMA actuators in order to produce the desired structural response efficiently with minimum power consumption. Due to the nonlinear behavior of the SMA actuator, it will be critical to incorporate a feedback control system that is able to accurately morph the structure by changing the strain of the composite structure. A Proportional–Integral–Derivative (PID) controller was designed to improve its tracking performance. Simulation on the control system showed that the PID controller produced acceptable response and managed to reduce steady state error for different types of input. The PID controller was then implemented in the experimental setup to control the smart composite plate. Results from the experiment illustrates that the smart structure system that has been designed per-formed effectively and the strain value of the composite structure can be controlled accurately

Effect of Sensor Location of Smart Composite Plate System on Feedback Control Performance

The present study is proposing a deflection control of a fiberglass composite plate system using shape memory alloy (SMA) actuators. The aim of this study is to determine the optimal placement of sensor for the feedback smart composite plate system. Strain measurement on the composite plate was chosen as the input variable for the feedback system. The change in strain on the composite plate was different at all locations on the plate during deflection. Thus, six strain gauges were placed at three positions i.e. tip, mid and root of the plate, at angle 0° and 45° in order to measure the change in strain at these locations and determine which is the best location to produce accurate control of the plate. The performance of the plate using these input variables were compared and analyzed by conducting experiments which required the plate to be deflected using the control system. In order to evaluate the performance of the controller under varying conditions, disturbances were also added to the experiments. The disturbances introduced were similar to those faced by aircraft during flight that is wind flow at varying velocities conducted in the wind tunnel. From the experimental results, it was found that the tip of the plate had the highest change in strain value and the control using input from the strain gauge located there produced the best performance as compared to input from strain gauges located at mid and root of the plate. However, in the presence of airflow, it was found that the best control performance was using feedback from the strain gauge located in the middle of the plate

Identification of modal properties of composite thin plate using OMA in wind tunnel environment

Identification of modal parameters is crucial especially in aerospace applications whereby the interactions of airflow with aircraft structures can result in undesirable structural deformations. This structural deformation can be predicted with knowledge of the modal parameters. This can be achieved through conventional modal testing that requires a known excitation force in order to extract these dynamic properties. This technique can be experimentally complex because of the need for artificial excitation and it also does not represent actual operational condition. The current work presents part of research work that address the practical implementation of operational modal analysis (OMA) applied to a cantilevered hybrid composite plate exposed to low speed airflow in a wind tunnel. A single contactless sensing system via a laser vibrometer is employed to measure the response. OMA technique applied in a wind-on condition succeeded in extracting the modal parameters of the hybrid composite plate which correlate well with modal testing using impact hammer excitation

Analysis of labour market needs for engineers with enhanced knowledge in sustainable renewable energy solutions in the built environment in some Asian countries

Despite the rapid growth in the uptake of renewable energy technologies, the educational profile and the skills gained at University level do not always comply with the practical needs of the organisations working in the field. Furthermore, even though the residential sector has very high potential in curbing its CO2 emissions worldwide thus meeting the challenging goals set out by the international agreements, such reduction has been limited so far. Within this context, the 'Skybelt' project, co-funded by the EU under the framework of the Erasmus + programme aims at enhancing in several Universities of Asia and Europe the engineering skills of students of all level for application of sustainable renewable energy solutions in the built environment. With the target of increasing the employability of graduates and the impact of the project, a survey on the labour market needs for specialists with enhanced knowledge and skills in the topic of the project has been conducted in the related Asian countries. Hence, relevant industries, labour market organisations and other stakeholders have been interviewed and the main results of this analysis is reported in the present paper. As first outcome of this activity, the obtained results have been considered in the selection of the modules to be improved according to a student centred study approach

Effect of aspect ratios on longitudinal and lateral motions of unmanned aerial vehicle

The study of wing with varying aspect ratio is critical in the development of the morphing wing for Unmanned Aerial Vehicle (UAV). A morphing wing permits a change in the camber, aspect ratio, wing twist and wing sweep while simultaneously supporting structural wing loads. UAV with this wing design will be able to carry out multiple objectives mission. This paper investigates the effect of aspect ratio on the stability of the longitudinal and lateral motions of UAV. The poles of the motions are calculated and root locus for the motions are plotted to validate that the variable aspect ratio (VAR) wings sustain stability during symmetric changes in wing span. Preliminary study on the stability of a generic UAV shows that it remains stable for values of aspect ratio from 3 to 10

Parametric Evaluation of Wobble-Yoke Stirling Engine State Space Model

A conceptual design of Stirling engine suitable for onboard aircraft application is the motivation behind this study. The aim is to evaluate the suitability of the system to be integrated in aircraft as part of energy contributor by recycling the waste thermal energy. A parametric evaluation of an established Wobble-Yoke Stirling Engine state space model was performed to determine a suitable pre-compensator design that is able to produce the highest power output given the size and mass constraint. Simulation was performed using MATLAB in order to analyze the dynamic properties of the engine as a closed-loop system, with temperature, pressure and damping coefficient acting as controlling parameters. The parametric evaluation was conducted to determine the effect of assemble mass of piston, maximum displacement of piston and viscous damping coefficient to the performance of the system. The methodology can be used in the conceptual design process in order to determine the sizing and power output of the stirling engine system

Development of an aircraft load planning system for distribution of passenger baggage

Airplane has been widely used as transportation compared to ship or car due to the short time journey. This phenomenon contributes to high demand or airline network for many places around the world and resulted in more competition for the airline industry due to changes in economy and increase in number of airlines. Besides, the increase in price of fuel can also be a major burden to the airline to maintain or gain profit. In order to overcome the fuel and cost problem, few measures can be taken including implementing effective aircraft loading system to optimize fuel weight and manage centre of gravity (CG), an aerodynamically clean aircraft, flight planning based on good data and optimal use of systems for example bleed, flaps and gear. For this study, load planning system for a Boeing 737-800 aircraft is considered to obtain a good position of CG for better fuel consumption. A load planning system was designed and developed using LabVIEW 2016 which can easily be integrated with sensors to produce a complete system. This system capable of receiving baggage weight as input and arranging the baggage to ensure the CG location is within the stipulated range. The efficiency of this system was validated by testing an aircraft model inside a wind tunnel and observing the performance of the aircraft when loads were arrange randomly and also based on the proposed arrangement by the system. As a result from the testing, by arranging the loads using the system that has been developed, a better flight performance in term of lift to drag ratio can be obtained which was 10.2 compared to randomly arranging the loads which was 7.9. Thus, by having a good load planning can reduce the fuel consumption and also improve the flight performance