Acoustic and Dynamic Response of Unbaffled Plates of Arbitrary Shape

In this study, a method for determining the effects of fluids on the dynamic characteristics of an aerospace structure and the response of the structure when it is excited by the acoustical loads produced during a rocket launch, has been developed. Elevated acoustical loads are critical in the design of large lightweight structures, such as solar arrays and communication reflectors, because of the high acceleration levels. The acoustic field generated during rocket launch can be considered as a diffuse field composed of many uncorrelated incident plane waves traveling in different directions, which impinge on the structure. A boundary element method was used to calculate the pressure jump produced by an incoming plane wave on an unbaffled plate and the fluid–structure coupled loads generated through plate vibration. This method is based on Kirchhoff’s integral formulation of the Helmholtz equation for pressure fields. The generalized force matrix attributed to the fluid loads was then formulated, taking the modes of the plate in vacuum as base functions of the structural displacement. These modes are obtained using a finite-element model. An iteration procedure was developed to calculate the natural frequencies of the fully coupled fluid–plate system. Comparison of the results obtained using the proposed method with those of other theories and experimental data demonstrated its efficiency and accuracy. The proposed method is suitable for analyzing plates of arbitrary shape subjected to any boundary conditions in a diffuse field for low to medium values of the frequency excitation range.

Significance of Nut Factor in Fastening of Joints in Engineering Structures

Threaded fasteners are category of bolts used in the joint assembling of aerospace structure. Torque is the process of applying a force that works at a circular distance and rotates the threaded fasteners at the bolted joints of these structures. With the aid of this torqueing force the two different parts are clamped together to form the joints. Due to torqueing there arises an opposing force which is known as the frictional force. The frictional force in threaded portion of the bolt transforms the applied Torque into stress. Due to this stress there is a chance of joint loosening or bolt fracture which is considered to be critical. Hence, selection of torqueing force for a desired preload is a major issue in joint deployment. The friction coefficient is a key factor for estimating the torque that is required for the fasteners to be deployed in the aerospace structures. There are many features which influence the friction coefficient for example size, pitch, thread tolerance. Till date only experimental methods and theoretical formulae has been used to estimate the friction coefficient, torque and preload. This paper identified the key features which are most correlated to coefficient of friction using the fisher score filtering technique and ca boost algorithm for both numerical and categorical datatypes. Along with that gives the insight on the torque, preload and coefficient of friction which are associated in fastening of the bolted joint in different non-permanent aerospace structures.

Modelling of the Aerospace Structure Demonstrator Subcomponent

Carbon-epoxy composite materials, due to their high strength in relation to mass, are increasingly used in the construction of aircraft structures, however, they are susceptible to a number of damages. One of the most common is delamination, which is a serious problem in the context of safe operation of such structures. As part of the TEBUK project, the Institute of Aviation has developed a methodology for forecasting the propagation of delamination. In order to validate the proposed method, an aerial structure demonstrator, modelled on the horizontal stabilizer of the I-23 Manager aircraft, was carried out. However, in order to carry out the validation, it was necessary to "simplify" the demonstrator model. The paper presents a numerical analysis conducted in order to separate from the TEBUK demonstrator model a fragment of the structure, which was used to study the delamination area, as an equivalent of the whole demonstrator. Subcomponent selection was carried out in several stages, narrowing down the analysed area covering delamination in subsequent steps and verifying the compliance of specific parameters with the same parameters obtained in a full demonstrator model. The parameters compared were: energy release rate values on the delamination front line and strain values in the delamination area. The numerical analyses presented in the paper were performed with the use of the MSC.Marc/Mentat calculation package. As a result of the analyses, a fragment of the structure was selected, which allows to significantly reduce the time and labour consumption of the production of the studied object, as well as to facilitate experimental research.

Graphene–magnesium nanocomposite: An advanced material for aerospace application

This work focuses on the analytical study of mechanical and thermal properties of a nanocomposite that can be obtained by reinforcing graphene in magnesium. The estimated mechanical and thermal properties of graphene–magnesium nanocomposite are much higher than magnesium and other existing alloys used in aerospace materials. We also altered the weight percentage of graphene in the composite and observed mechanical and thermal properties of the composite increase with increase in concentration of graphene reinforcement. The Young’s modulus and thermal conductivity of graphene–magnesium nanocomposite are found to be [Formula: see text][Formula: see text]165 GPa and [Formula: see text][Formula: see text]175 W/mK, respectively. Nanocomposite material with desired properties for targeted applications can also be designed by our analytical modeling technique. This graphene–magnesium nanocomposite can be used for designing improved aerospace structure systems with enhanced properties.