An Artificial Neural Network based approach for impact detection on composite panel for aerospace application

Fleet maintenance and safety aspects represent a strategic aspect in the managing of the modern aircraft fleets. The demand for efficient techniques of system and structure’s monitoring represent so a key aspect in the design of new generation aircraft. This is even more significant for composite structures that can be highly susceptible to delamination of the ply, which is often very difficult to detect externally and can lead to a dramatic reduction of design strength and service life, as a consequence of impact damage. The purpose of the work is the presentation of an innovative application within the Non Destructive Testing field based upon vibration measurements. The aim of the research has been the development of a Non Destructive Test (NDT) which meets most of the mandatory requirements for effective health monitoring systems while, at the same time, reducing as much as possible the complexity of the data analysis algorithm and the experimental acquisition instrumentation

Numerical Simulation For ANN Training and validation For Impact Detection

Composite structures, today, have a relevant role in our life. The most of the object we use daily are done of composite materials. The recent increase in use of composite materials can be explained if we consider: * They have great strength; * They have low weight; The combination of these two characteristics is the main reason the composite materials are so appreciate in engineering. Every time we need to produce a light structure with high strength composite materials are the good approach to design it. Instead of benefits, composite materials have also some issues. From a structural point of view the most critical is the difficult to monitoring them. Metal materials integrity is easy to check, the most of the time a visual inspection is enough to detect failures also in early stage. In composite materials, due the way they are maiden, often is impossible detect failures until it is too late to repair them. The most common problem composite materials have is the delamination. It consists in a detachment of plys inside the material due to an impact on the material itself. From an exterior point of view it is impossible to detect by eye. It suddenly propagates inside the structure inducing failures. The task of this work is to develop an artificial neural network (ANN) able to detect impacts and restrict the part of structure to monitor looking for damages. I

Acoustic properties of materials: A comparison of numerical and experimental methods

Acoustic simulations provide today a valid tool to simulate complex environments and complex interaction between acoustic and structure. Multiple methods are nowadays available with different degrees of accuracy and different applications. Simulation methods cover a wide frequency range with FE methods dominating the low frequency range. SEA mostly covers high frequency range with BEM covering an intermediate frequency range. Ray-tracing can work on the entire frequency range and is used when a large domain must be simulated. These methods require acoustic properties of materials to be implemented such as acoustic impedance or absorption and STL. The aim of this paper is to show different methods to provide these properties and discuss about the equivalence/difference of the numerical and experimental approaches under specific assumptions

ANALYTICAL AND NUMERICAL MODELS FOR THE AERODYNAMIC NOISE PREDICTION OF AN HIGH-SPEED TRAIN PANTOGRAPH

The present work deals with the aeroacoustic analysis of a three-dimensional pantograph model, through the employment of an innovative analytical approach and a 3D numerical modeling. Specifically, the proposed analytical approach, aimed to predict the noise emission, is based on a modified formulation of the Smith and Chow's formula. Namely, by considering the entire landing gear structure as a sum of cylindrical elements, each cylinder noise has been individually calculated by the formula, as a result, based on the superposition principle, the whole noise is obtained; considering that the pantograph can also be considered as a sum of cylindrical elements, this formula, initially developed for aircraft landing gears, has been optimized and calibrated for the purpose of the present study. Because of, the analytical formula does not take obviously into account several effects related to the noise generation mechanism, a 3D numerical aeroacoustic model of the pantograph was needed. Specifically, the theoretical background adopted is the Williams and Hawkings acoustic analogy, an evolution of the well-known Lighthill acoustic analogy. The latter consists in the substitution of the noise generating surface with a distribution of dipole punctual sound sources, whose intensity is proportional to the temporal variation of fluid dynamic quantities acting in that point. As a result, a more detailed characterization of the noise spectrum can be provided. The analytical and numerical results have been then compared in terms of sound pressure levels and a well spectral contents, to themselves and to available experimental data

Complex composite technology investigation: Simulations and experimental results

The paper deals with discussion of research activities within ITEMB (InTEgrated Full Composite Main landing gear Bay Concept) framework, an EU Clean Sky 2 program coordinated by Airbus. The driving motivation for the investigation on such a technology was found in the opportunity to design a main landing gear bay in a full composite configuration: Rational approaches have been implemented in an efficient testing stage providing the necessary database for the static qualification of the conceived design. Advanced and innovative solutions for a "more integrated" system were duly analysed and experimentally validated thus proving the overall device compliance with industrial standards and applicable airworthiness requirements

Manufacturing and Validation of a Novel Composite Component for Aircraft Main Landing Gear Bay

Composite materials may reduce the final weight of the aircraft structural components, in addition to improve fatigue performance and corrosion resistance. In order to achieve the optimization of air transport systems, making them increasingly sustainable, the structural design must be surely reviewed, starting to follow the ‘‘composite thinking’’ philosophy. The present research provides some relevant outcomes concerning the design of a composite sample for the main landing gear bay of a large commercial airplane (EASA CS25 category), within ITEMB (integrated full composite main landing gear bay concept) project, a program of Clean Sky 2 EU research framework. The most ambitious goal is to develop a new generation of lower center fuselage (LCF) with an innovative integrated landing system in the fuselage, which is considered the next frontier in the development of landing systems for medium-haul aircraft, such as the Airbus A320 aircraft family. The development of a different architecture, with the landing gear integrated within the related fuselage bay, could lead to a simplification of the whole subassembly with potential advantage in terms of construction and assembly times. Final target of the project is the manufacturing of an innovative monolithic composite structure that will replace the actual configuration (a mixed structure of metal and composite subassemblies) reducing or actually removing all the cost of assembly and increasing the production rate. This paper presents the main results of the work, introducing the main processing steps and prototype results; in the last part of the work, also some experimental tests on significant element are introduced as the first assessment of the technology readiness level that has been achieved

Numerical and Experimental Acoustic Performance Investigations of a High-Speed Train Composite Sandwich Panel

Present work focuses on the implementation of numerical and experimental analyses aimed to acoustic performances characterization of a composite sandwich panel used for a high-speed train. Firstly, an experimental and a numerical modal analyses are presented. Starting from both FE simulation and impact testing outcomes, it has been possible to carry out a correlation study through the computation of the Modal Assurance Criterion (MAC). Good agreement between numerical and experimental analyses has been found, therefore the definition of a reliable FE model has been obtained without the necessity of implementing a sensitivity and updating procedure. In this paper, to find a convenient and accurate mean for predicting the panel Transmission Loss parameter, the panel is modeled as a composite sandwich panel, and its TL is predicted with the hybrid FE&SEA (Statistical Energy Analysis) method. The TL result is then compared to the experimental one, carried out through the employment of an intensity sound probe. A very good accordance has been found allowing to use such numerical procedure for further acoustic performances improvements. Hence, future developments could regard the possibility to implement a Reverse Engineering procedure, in order to realize an optimization process by considering different materials and stratifications or different panel thicknesses, to improve the acoustic attenuation properties at those frequencies at which a worse acoustic behavior of the panel, is present

AN INNOVATIVE NUMERICAL APPROACH FOR TRAIN PASS-BY NOISE FORECASTING

This paper deals with an engineering method for the prediction of vehicle pass-by noise based on a FEM/ BEM exterior acoustic calculation in the frequency domain. The researchers simulate, in a virtual environment, the experimental outdoor pass-by noise measurement. The simulated pass-by noise campaign is synthesized from multiple acoustic transfer functions between a line of virtual microphones located 7.5m on the side of the vehicle and each noise source. A numerical FEM/BEM train bogie acoustic model has been created within the MSC ACTRAN commercial softwares. Wheel-rail rolling noise, engine and powertrain noise acoustic source have been implemented and posi-tioned inside the FEM and BEM model to demonstrate the validity of the proposed methods. The contribu-tion from noise sources, expressed both in terms of sound pressure level and overall value, to the pass-by noise were evaluated up to 5 kHz. The virtual pass-by-noise assessment has been then validated by experi-mental measurement of the complete four coach’s train with respect to different speed regimes