The Experts below are selected from a list of 17052 Experts worldwide ranked by ideXlab platform

Keith Worden - One of the best experts on this subject based on the ideXlab platform.

  • Impact detection in an aircraft Composite Panel-A neural-network approach
    Journal of Sound and Vibration, 2007
    Co-Authors: J. R. Leclerc, Wiesław J. Staszewski, Keith Worden, Jim Haywood
    Abstract:

    This paper presents the latest results from a programme of work aiming to design impact detectors for structures. The results are from an aircraft component which is substantially more complex than the structures previously investigated by the authors. The paper also illustrates three different approaches to the impact location problem, namely, regression, classification and a combination of both. © 2006.

  • an automatic impact monitor for a Composite Panel employing smart sensor technology
    Smart Materials and Structures, 2005
    Co-Authors: Jonathan Haywood, Wiesław J. Staszewski, P T Coverley, Keith Worden
    Abstract:

    Impacts can inflict serious damage on Composite structures. For structures on the surface of an aircraft this has potentially critical consequences. The problem is exacerbated by the fact that the damage is internal, with little or no indication on the surface of the structure, making it difficult to detect. A potential solution to the problem would be an impact monitoring system that could detect when an impact occurred. This idea was explored using a Composite Panel, inside which a SMART Layer was embedded. Two techniques were studied that were able to estimate the locations of impacts on the Panel from the measurements provided by the piezoelectric strain sensors in the SMART Layer. The first technique employed artificial neural networks and the second used a triangulation procedure incorporating a genetic algorithm. The knowledge acquired during the study made it possible to develop a simple and efficient prototype impact monitoring system for the Composite Panel.

  • impact location and quantification on a Composite Panel using neural networks and a genetic algorithm
    Strain, 2000
    Co-Authors: Keith Worden, Wiesław J. Staszewski
    Abstract:

    Abstract: The problem of impact detection in Composite Panels using artificial neural networks is addressed in this paper. The data were taken from an experiment in which time dependent strain data were recorded on a network of surface-mounted piezoceramic sensors when the plate was impacted. Neural networks were trained to locate and quantify the impact event when presented with features extracted from the measured data. An important problem for detection systems like this is that of optimal sensor placement; this is solved here by means of a Genetic Algorithm. The study shows that a relatively small number of sensors can be used to detect reliably impacts on a Composite plate.

Brian Falzon - One of the best experts on this subject based on the ideXlab platform.

  • Predicting low-velocity impact damage on a stiffened Composite Panel
    Composites Part A-applied Science and Manufacturing, 2010
    Co-Authors: Andrea Faggiani, Brian Falzon
    Abstract:

    Abstract An intralaminar damage model, based on a continuum damage mechanics approach, is presented to model the damage mechanisms occurring in carbon fibre Composite structures incorporating fibre tensile and compressive breakage, matrix tensile and compressive fracture, and shear failure. The damage model, together with interface elements for capturing interlaminar failure, is implemented in a finite element package and used in a detailed finite element model to simulate the response of a stiffened Composite Panel to low-velocity impact. Contact algorithms and friction between delaminated plies were included, to better simulate the impact event. Analyses were executed on a high performance computer (HPC) cluster to reduce the actual time required for this detailed numerical analysis. Numerical results relating to the various observed interlaminar damage mechanisms, delamination initiation and propagation, as well as the model’s ability to capture post-impact permanent indentation in the Panel are discussed. Very good agreement was achieved with experimentally obtained data of energy absorbed and impactor force versus time. The extent of damage predicted around the impact site also corresponded well with the damage detected by non destructive evaluation of the tested Panel.

  • postbuckling behaviour of a blade stiffened Composite Panel loaded in uniaxial compression
    Composites Part A-applied Science and Manufacturing, 2000
    Co-Authors: Brian Falzon, K A Stevens, G A O Davies
    Abstract:

    Abstract The postbuckling behaviour of a Panel with blade-stiffeners incorporating tapered flanges was experimentally investigated. A new failure mechanism was identified for this particular type of stiffener. Failure was initiated by mid-plane delamination at the free edge of the postbuckled stiffener web at a node-line. This was consistent with an interlaminar shear stress failure and was calculated from strain gauge measurements using an approximate analysis based on lamination theory and incorporating edge effects. The critical shear stress was found to agree well with the shear strength obtained from a three-point bending test of the web laminate.

Yurim Park - One of the best experts on this subject based on the ideXlab platform.

  • low velocity impact localization in a stiffened Composite Panel using a normalized cross correlation method
    Smart Materials and Structures, 2015
    Co-Authors: Yurim Park
    Abstract:

    This paper presents an experimental study on the low-velocity impact localization of complex Composite structures. An impact localization algorithm, which localizes an impact source by comparing the normalized cross-correlation between the reference database and the obtained impact signals, was proposed. The proposed method was applied to a stiffened Composite Panel that consists of a main spar and stringers. Impact tests were conducted on the Composite Panel in which four multiplexed fiber Bragg grating (FBG) sensors were attached on the bottom surface. The verification results indicated that 20 verification points were successfully localized with the maximum error of 43.98 mm and average error of 14.23 mm using four FBG sensors. The effect of the number of sensors on the localization performance was also investigated. The comparison results revealed that the proposed method could localize an impact source using a reduced number of sensors. A single FBG sensor covered an area of 600 × 900 mm2 of the stiffened Composite Panel with a maximum error of 64.76 mm and an average error of 17.86 mm using the proposed method.

A K Mal - One of the best experts on this subject based on the ideXlab platform.

  • autonomous impact damage monitoring in a stiffened Composite Panel
    Journal of Intelligent Material Systems and Structures, 2007
    Co-Authors: Sauvik Banerjee, Fabrizio Ricci, Ernesto Monaco, Leonardo Lecce, A K Mal
    Abstract:

    This study is concerned with the detection and characterization of impact damage in a stiffened woven Composite structure using high frequency Lamb waves and low frequency modal vibrations. The geometric and material complexities of the structure present practical difficulties in the direct analysis of both wave propagation and modal vibration data using theoretical constructs. Improved ultrasonic and vibration test setups consisting of distributed, high fidelity, and surface mounted sensor arrays are used here to determine changes in the dynamical properties of the Composite structural components in the presence of damage. The sensors are assumed to provide both the low frequency global response (i.e., modal frequencies and mode shapes) of the structure to external loads and the (local) high frequency signals due to wave propagation effects in either passive or active mode of the ultrasonic array. A damage index, comparing the measured dynamical response of two successive states of the structure is introduced as a determinant of structural damage. The method relies on the fact that the dynamical properties of a structure change with the initiation or growth of damage. A diagnostic imaging tool is used for the interpretation and graphical representation of the indices to enable automated monitoring of the changes in the indices at a given instant of time. The value of the index at a given sensor increases with the proximity of the damage to the sensor. A sensitivity analysis is carried out in an effort to determine a threshold value of the index below which no reliable information about the state of health of the structure can be estimated. It is shown that the automated procedure is able to identify a defect right from its appearance, with some degree of confidence. The feasibility of developing a practical intelligent structural health monitoring system (ISHMS), based on the concept of 'a structure requesting service when needed,' is discussed.

T E Tay - One of the best experts on this subject based on the ideXlab platform.

  • traction separation laws for progressive failure of bonded scarf repair of Composite Panel
    Composite Structures, 2011
    Co-Authors: M Ridha, V B C Tan, T E Tay
    Abstract:

    Abstract Repair of Composites has become of considerable importance recently as modern commercial airliners employ much more Composites in their airframes then previously. Major maintenance, repair, and overhaul (MRO) centers must contend with issues of damage tolerance, efficiency, integrity and cost of repairs. Computational methods have been developed to sufficiently sophisticated levels to aid in the design, evaluation and optimization of proposed repair schemes before they are implemented, potentially saving time and cost. In this paper, parametric studies on progressive failure analysis of a bonded scarf repair of a Composite Panel was performed. The study finds that finite element models with an appropriate material property degradation scheme using the micromechanics of failure criterion are able to predict the failure load of undamaged and damaged specimen. Results of the parametric studies on adhesive properties suggest that the failure stress of a repaired Composite Panel is more sensitive to the strength of the cohesive elements than to its toughness when a linear or trapezoidal softening traction–separation law is used, but the influence of adhesive strength is not significant when exponential softening traction–separation law is used.