Delamination Identification in Stiffened Composite Panels Using Surface Strain Data

2017 ◽  
Vol 754 ◽  
pp. 379-382
Author(s):  
George Lampeas ◽  
Christos Katsikeros ◽  
Konstantinos Fotopoulos
Keyword(s):  
Strain Field ◽  
Structural Integrity ◽  
Decomposition Methods ◽  
Surface Strain ◽  
Composite Panel ◽  
Data Decomposition ◽  
Full Field ◽  
Stiffened Composite Panels ◽  
Strain Data ◽  
Efficient Processing

The structural integrity of a composite structure can be greatly compromised by damage inside the component. Invisible damage, e.g. caused by low-speed impact, can significantly reduces composite components capability to efficiently carry loads. In the present study, an innovative approach of strain-based delamination identification and localization is investigated, based on the efficient processing of full-field surface strain measurements. Surface strain data, potentially derived by full-field optical methodologies are used in the assessment of the delamination pattern, through strain field perturbations caused due to damage evolution. Relations between delamination damage and surface strain field disturbances are established by exploiting data decomposition methods using Zernike polynomial moments. The methodology is successfully demonstrated in the case of a stiffened composite panel.

scholarly journals Full-Field Strain Reconstruction Using Uniaxial Strain Measurements: Application to Damage Detection

2021 ◽  
Vol 11 (4) ◽  
pp. 1681
Author(s):  
Rinto Roy ◽  
Marco Gherlone ◽  
Cecilia Surace ◽  
Alexander Tessler
Keyword(s):  
Uniaxial Strain ◽  
Surface Strain ◽  
Internal Crack ◽  
Full Field ◽  
Strain Measurements ◽  
Reconstruction Performance ◽  
Strain Smoothing ◽  
Strain Data ◽  
Position And Orientation ◽  
Displacement Reconstruction

This work investigates the inverse problem of reconstructing the continuous displacement field of a structure using a spatially distributed set of discrete uniaxial strain data. The proposed technique is based on the inverse Finite Element Method (iFEM), which has been demonstrated to be suitable for full-field displacement, and subsequently strain, reconstruction in beam and plate structures using discrete or continuous surface strain measurements. The iFEM uses a variationally based approach to displacement reconstruction, where an error functional is discretized using a set of finite elements. The effects of position and orientation of uniaxial strain measurements on the iFEM results are investigated, and the use of certain strain smoothing strategies for improving reconstruction accuracy is discussed. Reconstruction performance using uniaxial strain data is examined numerically using the problem of a thin plate with an internal crack. The results obtained highlight that strain field reconstruction using the proposed strategy can provide useful information regarding the presence, position, and orientation of damage on the plate.

scholarly journals Filament wound composite fatigue mechanisms investigated with full field DIC strain monitoring

2021 ◽  
Vol 11 (1) ◽  
pp. 401-413
Author(s):  
Eivind Hugaas ◽  
Andreas T. Echtermeyer
Keyword(s):  
Strain Field ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Image Correlation ◽  
Catastrophic Failure ◽  
Fiber Failure ◽  
Full Field ◽  
Matrix Cracks ◽  
Filament Wound ◽  
Over Time

Abstract Fatigue of filament wound materials was investigated using Digital Image Correlation DIC monitoring every 50th cycle of a high cycle fatigue test of a split disk ring sample. The ring was cut from a filament wound glass fiber reinforced polymer pressure vessel and had a hole. The strain field redistributed over time, lowering and moving strain concentrations. The redistributive behavior was most extensive in areas that later developed local fiber failure, which soon led to catastrophic failure. Microscopy was carried out on partially fatigued material. Damage evolved as matrix cracks and matrix splitting of groups of fibers and complete debonding of single fibers. This occurred at borders of voids and matrix cracks, easing progressive fiber failure. It was concluded that fatigue in filament wound composites has an extensive matrix damage phase before final failure. Fibers could locally withstand strains close to and above the static failure strain for considerable number of cycles if little local strain field redistribution was observed. The used method was able to detect changes in the strain fields that preceded catastrophic failure. It was concluded that DIC combined with the post processing methods presented may serve as a valuable tool for structural integrity monitoring of composite pressure vessels over time.

Modeling of Contact Patch in Dual-Chamber Pneumatic Tires

2018 ◽  
Vol 46 (2) ◽  
pp. 78-92 ◽  
Author(s):  
A. I. Kubba ◽  
G. J. Hall ◽  
S. Varghese ◽  
O. A. Olatunbosun ◽  
C. J. Anthony
Keyword(s):  
Strain Sensors ◽  
Surface Strain ◽  
Wireless Data ◽  
Data Logger ◽  
Dual Chamber ◽  
Piezoelectric Polymer ◽  
Pure Rolling ◽  
Piezoelectric Elements ◽  
Strain Data ◽  
Deformation Patterns

ABSTRACT This study presents an investigation of the inner tire surface strain measurement by using piezoelectric polymer transducers adhered on the inner liner of the tire, acting as strain sensors in both conventional and dual-chamber tires. The piezoelectric elements generate electrical charges when strain is applied. The inner liner tire strain can be found from the generated charge. A wireless data logger was employed to measure and transmit the measured signals from the piezoelectric elements to a PC to store and display the readout signals in real time. The strain data can be used as a monitoring system to recognize tire-loading conditions (e.g., traction, braking, and cornering) in smart tire technology. Finite element simulations, using ABAQUS, were employed to estimate tire deformation patterns in both conventional and dual-chamber tires for pure rolling and steady-state cornering conditions for different inflation pressures to simulate on-road and off-road riding tire performances and to compare with the experimental results obtained from both the piezoelectric transducers and tire test rig.

scholarly journals Full-Field Operational Modal Analysis of an Aircraft Composite Panel from the Dynamic Response in Multi-Impact Test

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1602
Author(s):  
Ángel Molina-Viedma ◽  
Elías López-Alba ◽  
Luis Felipe-Sesé ◽  
Francisco Díaz
Keyword(s):  
Modal Analysis ◽  
Energy Absorption ◽  
High Speed ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Image Correlation ◽  
Composite Panel ◽  
Impact Excitation ◽  
Full Field ◽  
The Impact

Experimental characterization and validation of skin components in aircraft entails multiple evaluations (structural, aerodynamic, acoustic, etc.) and expensive campaigns. They require different rigs and equipment to perform the necessary tests. Two of the main dynamic characterizations include the energy absorption under impact forcing and the identification of modal parameters through the vibration response under any broadband excitation, which also includes impacts. This work exploits the response of a stiffened aircraft composite panel submitted to a multi-impact excitation, which is intended for impact and energy absorption analysis. Based on the high stiffness of composite materials, the study worked under the assumption that the global response to the multi-impact excitation is linear with small strains, neglecting the nonlinear behavior produced by local damage generation. Then, modal identification could be performed. The vibration after the impact was measured by high-speed 3D digital image correlation and employed for full-field operational modal analysis. Multiple modes were characterized in a wide spectrum, exploiting the advantages of the full-field noninvasive techniques. These results described a consistent modal behavior of the panel along with good indicators of mode separation given by the auto modal assurance criterion (Auto-MAC). Hence, it illustrates the possibility of performing these dynamic characterizations in a single test, offering additional information while reducing time and investment during the validation of these structures.

Study on Displacement Measurement for Induced Strain Field Based on Digital Speckle Pattern Interferometry Method

2013 ◽  
Vol 273 ◽  
pp. 510-514
Author(s):  
Jing Liu ◽  
Hui Zhang ◽  
Jun Li ◽  
Da Chuan Chen ◽  
Yan Kun Tang
Keyword(s):  
Strain Field ◽  
High Speed ◽  
Speckle Pattern ◽  
Measuring Method ◽  
Full Field ◽  
Digital Speckle Pattern Interferometry ◽  
Level Measurement ◽  
On Line ◽  
Interferometry Method ◽  
Digital Speckle

Digital Speckle Pattern Interferometry ( DSPI for short ) method has become one of the most practical worthy techniques for speckle measuring methods with the high-speed development of optic-electronical technique, image processing technology and electronic computer technology. There is a lot of advantages about it, such as uncomplicated operation, non-contacting, advanced automatic level, measurement on-line and extensive using. In this thesis, the displacement variation of the induced strain field for driving by piezoelectric ceramics can be measured by using this method. Thus we can come to a conclusion that digital speckle pattern interferometry is a new measuring method for extracting small-signal. It also provides a powerfully theoretical and experimental platform for study of automated, full-field, high-precision and nondestructive measurement.

An Approach to Approximate the Full Strain Field of Turbofan Blades During Operation

2018 ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu ◽  
Walter O’Brien
Keyword(s):  
Numerical Model ◽  
Cantilever Beam ◽  
Strain Field ◽  
Measured Data ◽  
Mode Shapes ◽  
Beam Model ◽  
Reference Solution ◽  
Full Field ◽  
Field Response ◽  
Critical Locations

The measurement of the aeromechanical response of the fan blades is important to quantifying their integrity. The accurate knowledge of the response at critical locations of the structure is crucial when assessing the structural condition. A reliable and low cost measuring technique is necessary. Currently, sensors can only provide the measured data at several discrete points. A significant number of sensors may be required to fully characterize the aeromechanical response of the blades. However, the amount of instrumentation that can be placed on the structure is limited due to data acquisition system limitations, instrumentation accessibility, and the effect of the instrumentation on the measured response. From a practical stand point, it is not possible to place sensors at all the critical locations for different excitations. Therefore, development of an approach that derives the full strain field response based on a limited set of measured data is required. In this study, the traditional model reduction method is used to expand the full strain field response of the structure by using a set of discrete measured data. Two computational models are developed and used to verify the expansion approach. The solution of the numerical model is chosen as the reference solution. In addition, the numerical model also provides the mode shapes of the structure. In the expansion approach, this information is used to develop the algorithm. First, a cantilever beam model is created. The influences of the sensor location, number of sensors and the number of modes included are analyzed using this cantilever beam model. The expanded full field response data is compared with the reference solution to evaluate the expansion procedure. The rotor 67 blade model is then used to test the expansion method. The results show that the expanded full field data is in good agreement with the calculated data. The expansion algorithm can be used for the full field strain by using the limited sets of strain data.

scholarly journals Non-Destructive Evaluation of Damage Mechanisms in Composite Sandwich Structure

2008 ◽  
Vol 13-14 ◽  
pp. 105-114
Author(s):  
Amit Puri ◽  
Alexander D. Fergusson ◽  
I. Palmer ◽  
Andrew Morris ◽  
F. Jensen ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Structural Integrity ◽  
Wind Turbine Blade ◽  
Image Correlation ◽  
Box Girder ◽  
Full Field ◽  
Composite Sandwich ◽  
Non Destructive ◽  
Dic Technique

This paper presents the experimental results obtained of flexurally loaded wind turbine blade cross section material. All material was extracted from a wind turbine blade box girder and testing was conducted in four point configuration. The aim was to gain an understanding of the structural integrity of this lightweight material as it deforms in flexure. To allow for thorough analysis, digital image correlation (DIC) was used to produce full field strain maps of the deforming specimens. Results highlight the capability of the DIC technique to identify regions of failure, as well as the aspects responsible for them. Overall, the results present a foundation for tests on larger substructure, and eventually integration into manufacturing and maintenance aspects of the industry.

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