scholarly journals Wave Interaction with Defects in Pressurised Composite Structures

2018 ◽  
Vol 37 (3) ◽  
Author(s):  
R. K. Apalowo ◽  
D. Chronopoulos ◽  
G. Tanner
Keyword(s):  
Composite Structures ◽  
Wave Interaction

scholarly journals Application of PZT Ceramic Sensors for Composite Structure Monitoring Using Harmonic Excitation Signals and Bayesian Classification Approach

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5468
Author(s):  
Michal Dziendzikowski ◽  
Mateusz Heesch ◽  
Jakub Gorski ◽  
Krzysztof Dragan ◽  
Ziemowit Dworakowski
Keyword(s):  
Elastic Wave ◽  
Composite Structures ◽  
Nearest Neighbor ◽  
Impact Damage ◽  
Asymptotic Properties ◽  
Wave Interaction ◽  
Principal Component ◽  
Harmonic Excitation ◽  
Structure Monitoring ◽  
Neighbor Classifier

The capabilities of ceramic PZT transducers, allowing for elastic wave excitation in a broad frequency spectrum, made them particularly suitable for the Structural Health Monitoring field. In this paper, the approach to detecting impact damage in composite structures based on harmonic excitation of PZT sensor in the so-called pitch–catch PZT network setup is studied. In particular, the repeatability of damage indication for similar configuration of two independent PZT networks is analyzed, and the possibility of damage indication for different localization of sensing paths between pairs of PZT sensors with respect to damage locations is investigated. The approach allowed for differentiation between paths sensitive to the transmission mode of elastic wave interaction and sensitive reflection mode. In addition, a new universal Bayesian approach to SHM data classification is provided in the paper. The defined Bayesian classifier is based on asymptotic properties of Maximum Likelihood estimators and Principal Component Analysis for orthogonal data transformation. Properties of the defined algorithm are compared to the standard nearest-neighbor classifier based on the acquired experimental data. It was shown in the paper that the proposed approach is characterized by lower false-positive indications in comparison with the nearest-neighbor algorithm.

scholarly journals Wave interaction with nonlinear damage and generation of harmonics in composite structures

2019 ◽  
Vol 230 ◽  
pp. 111495 ◽  
Author(s):  
R.K. Apalowo ◽  
D. Chronopoulos ◽  
S. Cantero-Chinchilla
Keyword(s):  
Composite Structures ◽  
Wave Interaction ◽  
Generation Of Harmonics

scholarly journals The impact of temperature on wave interaction with damage in composite structures

2017 ◽  
Vol 231 (16) ◽  
pp. 3042-3056 ◽  
Author(s):  
RK Apalowo ◽  
D Chronopoulos ◽  
M Ichchou ◽  
Y Essa ◽  
F Martin De La Escalera
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Composite Structures ◽  
Wave Interaction ◽  
Mechanical Analysis ◽  
Thermomechanical Properties ◽  
Launch Vehicles ◽  
Temperature Dependent ◽  
Transition Range ◽  
The Impact

The increased use of composite materials in modern aerospace and automotive structures, and the broad range of launch vehicles’ operating temperature imply a great temperature range for which the structures has to be frequently and thoroughly inspected. A thermal mechanical analysis is used to experimentally measure the temperature-dependent mechanical properties of a composite layered panel in the range of −100 ℃ to 150 ℃. A hybrid wave finite element/finite element computational scheme is developed to calculate the temperature-dependent wave propagation and interaction properties of a system of two structural waveguides connected through a coupling joint. Calculations are made using the measured thermomechanical properties. Temperature-dependent wave propagation constants of each structural waveguide are obtained by the wave finite element approach and then coupled to the fully finite element described coupling joint, on which damage is modelled, in order to calculate the scattering magnitudes of the waves interaction with damage across the coupling joint. The significance of the panel’s glass transition range on the measured and calculated properties is emphasised. Numerical results are presented as illustration of the work.

In Situ microscopy of the anodic etching of silicon

1995 ◽  
Vol 53 ◽  
pp. 232-233
Author(s):  
Frances M. Ross ◽  
Peter C. Searson
Keyword(s):  
Composite Structures ◽  
High Surface ◽  
High Surface Area ◽  
Chemical Properties ◽  
Selective Etching ◽  
Silicon On Insulator ◽  
Second Phase ◽  
Porous Layers ◽  
New Class ◽  
Porous Semiconductors

Porous semiconductors represent a relatively new class of materials formed by the selective etching of a single or polycrystalline substrate. Although porous silicon has received considerable attention due to its novel optical properties1, porous layers can be formed in other semiconductors such as GaAs and GaP. These materials are characterised by very high surface area and by electrical, optical and chemical properties that may differ considerably from bulk. The properties depend on the pore morphology, which can be controlled by adjusting the processing conditions and the dopant concentration. A number of novel structures can be fabricated using selective etching. For example, self-supporting membranes can be made by growing pores through a wafer, films with modulated pore structure can be fabricated by varying the applied potential during growth, composite structures can be prepared by depositing a second phase into the pores and silicon-on-insulator structures can be formed by oxidising a buried porous layer. In all these applications the ability to grow nanostructures controllably is critical.

Tidal Inlet Current — Ocean Wave Interaction

1972 ◽  
Author(s):  
Lyndell Z. Hales ◽  
John B. Herbich
Keyword(s):  
Wave Interaction ◽  
Tidal Inlet ◽  
Ocean Wave

A Numerical and Experimental Approach for Modeling Porosity Due to Entrapped Air and Volatiles Off-gassing During Manufacturing of Composite Structures

2019 ◽  
Author(s):  
Curtis Hickmott ◽  
Alireza Forghani ◽  
Victoria Hutten ◽  
Evan Lorbiecki ◽  
Frank Palmieri ◽  
...  
Keyword(s):  
Composite Structures ◽  
Experimental Approach ◽  
Entrapped Air
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