scholarly journals An Experimental and Numerical Study on the Use of Chirped FBG Sensors for Monitoring Fatigue Damage in Hybrid Composite Patch Repairs

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1168
Author(s):  
Rodolfo L. Rito ◽  
Stephen L. Ogin ◽  
Andrew D. Crocombe
Keyword(s):  
Numerical Study ◽  
Fatigue Cracks ◽  
Fatigue Loading ◽  
Bond Line ◽  
Fibre Bragg Grating ◽  
Sensor Location ◽  
Composite Patch ◽  
Film Adhesive ◽  
Patch Repairs ◽  
Tension Loading

In this paper, chirped fibre Bragg grating (CFBG) sensors used to monitor the structural health of a composite patch used to repair an aluminium panel is presented. To introduce damage, a notch was produced at the centre of an aluminium panel. The repair consisted of bonding a pre-cured composite patch to the host panel using an aerospace-grade film adhesive; the sensor was embedded in the bond-line during fabrication of the repair. The repaired panels were subjected to tension-tension loading in fatigue. Cracks initiated and grew from both ends of the notch in the aluminium panels and the fatigue loading was stopped periodically for short periods of time to record the reflected spectra from the sensor. It was found that perturbations in the reflected spectra began to occur when the crack was within about 2 to 3 mm of the sensor location; after the crack passed the sensor location, the perturbations essentially stabilised. Predicted reflected spectra have been found to be in good agreement with the experiment, confirming that CFBG sensors can detect crack growth in patch-repaired panels.

Acoustic emission detection and prediction of fatigue crack propagation in composite patch repairs using neural network

2016 ◽  
Vol 30 (1) ◽  
pp. 3-29 ◽  
Author(s):  
A Chukwujekwu Okafor ◽  
Navdeep Singh ◽  
Navrag Singh ◽  
Benjamin N Oguejiofor
Keyword(s):  
Acoustic Emission ◽  
Crack Propagation ◽  
Crack Length ◽  
Back Propagation ◽  
Fatigue Loading ◽  
Matrix Cracking ◽  
Composite Patch ◽  
Patch Repairs ◽  
Aluminum Panels ◽  
Emission Detection

This article presents the results of acoustic emission (AE) monitoring of crack propagation in 2024-T3 clad aluminum panels repaired with adhesively bonded octagonal and elliptical boron/epoxy composite patches using FM-73 adhesive under tension–tension fatigue loading. Two crack propagation gages and four broadband AE sensors were used to monitor crack initiation and propagation, respectively. The acquired AE signals were processed in time and frequency domain to identify sensor features correlated with fatigue cycle and crack propagation, which were used to train neural networks for predicting crack length. The results show that AE events are correlated with crack propagation, and crack propagation signals can be differentiated from signals due to matrix cracking, fiber breakage, and shear of the composite patch. Three back-propagation cascade feed-forward networks were trained to predict crack length using number of fatigue cycles, number of AE events, and number of fatigue cycles and number of AE events together as inputs, respectively. It was found that network with fatigue cycles as input gave good results, while the network with just AE events as input gave greater error. However, the network using both fatigue cycles and number of AE events as inputs to predict crack length gave much better results.

Experimental Control of Curing via Dielectric and Fibre Bragg Grating Sensors for Composite Patch Repairs

2011 ◽  
Vol 9 (4) ◽  
pp. 1265-1272 ◽  
Author(s):  
K. Kalkanis ◽  
G. J. Tsamasphyros ◽  
G. N. Kanderakis ◽  
N. Pantelelis ◽  
M. Tur ◽  
...  
Keyword(s):  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Experimental Control ◽  
Composite Patch ◽  
Patch Repairs

Relaxation of Residual Stresses in and around Mechanical Fasteners Due to Fatigue Loading

2006 ◽  
Vol 524-525 ◽  
pp. 153-158 ◽  
Author(s):  
Matthew E. Fox ◽  
Philip J. Withers
Keyword(s):  
Residual Stresses ◽  
Hoop Stress ◽  
Fatigue Cracks ◽  
Fatigue Loading ◽  
Far Field ◽  
Synchrotron Diffraction ◽  
Fastener Hole ◽  
Single Plate ◽  
Mechanical Fasteners ◽  
Hoop Stresses

The residual stresses around clearance-fit mechanical fasteners have been found to be similar to those around cold expanded holes where compressive hoop stresses close to the fastener hole are balanced by far-field tensile stresses. This compressive zone has been shown to prolong fatigue lifetimes around fastener holes. Constant amplitude fatigue loading was applied to single plate rivet specimens for varying numbers of cycles to investigate the redistribution of these stresses after fatiguing. Synchrotron diffraction was used to map the evolution of the residual stresses around the rivets. Little change in the hoop stress local to the rivets occurred until visible fatigue cracks were observed suggesting that relaxation of these stresses is due to the cracks rather than their cause.

General Method for Optimizing Composite Patch Repairs

2015 ◽  
Vol 1120-1121 ◽  
pp. 670-674
Author(s):  
Abdelmadjid Ait Yala ◽  
Abderrahmanne Akkouche
Keyword(s):  
Mechanical Properties ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Optimization Problem ◽  
Composite Patch ◽  
Matlab Program ◽  
Patch Repairs ◽  
Selection Of ◽  
General Method

The aim of this work is to define a general method for the optimization of composite patch repairing. Fracture mechanics theory shows that the stress intensity factor tends towards an asymptotic limit K∞.This limit is given by Rose’s formula and is a function of the thicknesses and mechanical properties of the cracked plate, the composite patch and the adhesive. The proposed approach consists in considering this limit as an objective function that needs to be minimized. In deed lowering this asymptote will reduce the values of the stress intensity factor hence optimize the repair. However to be effective this robust design must satisfy the stiffness ratio criteria. The resolution of this double objective optimization problem with Matlab program allowed us determine the appropriate geometric and mechanical properties that allow the optimum design; that is the selection of the adhesive, the patch and their respective thicknesses.

Modeling of Solder Fatigue Failure due to Ductile Damage

2010 ◽  
Vol 26 (4) ◽  
pp. N23-N27 ◽  
Author(s):  
K. Aluru ◽  
F.-L. Wen ◽  
Y.-L. Shen
Keyword(s):  
Numerical Study ◽  
Fatigue Cracks ◽  
Damage Model ◽  
Quantitative Information ◽  
Ductile Damage ◽  
Element Analysis ◽  
Cyclic Shear ◽  
Rate Dependent ◽  
Solder Fatigue ◽  
Temporal And Spatial

ABSTRACTA numerical study is undertaken to simulate failure of solder joint caused by cyclic shear deformation. A progressive ductile damage model is incorporated into the rate-dependent elastic-viscoplastic finite element analysis, resulting in the capability of simulating damage evolution and eventual failure through crack formation. It is demonstrated that quantitative information of fatigue life, as well as the temporal and spatial evolution of fatigue cracks, can be explicitly obtained.

Estimation of the Shape Evolution and the Growth History of an Embedded Crack by Fatigue Loading

2011 ◽  
Author(s):  
Koji Gotoh ◽  
Keisuke Harada ◽  
Yosuke Anai
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Estimation Method ◽  
Estimation Procedure ◽  
Fatigue Loading ◽  
Shape Evolution ◽  
Crack Growth Behaviour ◽  
Embedded Crack

Fatigue life estimation for planar cracks, e.g. part-through surface cracks or embedded cracks is very important because most of fatigue cracks found in welded built-up structures show planar crack morphologies. Fatigue crack growth behaviour of an embedded crack in welded joints is investigated in this study. The estimation procedure of crack shape evolution for an embedded crack is introduced and validation of the estimation procedure of fatigue crack growth based on the numerical simulation of fatigue crack growth with EDS concept for an embedded crack is performed. The validity of the proposed shape evolution estimation method and the fatigue crack growth simulation based on the fracture mechanics approach with EDS concept are confirmed.

A review on composite patch repairs and the most important parameters affecting its efficiency and durability

2020 ◽  
pp. 073168442094160
Author(s):  
Sirvan Mohammadi ◽  
Mohammad Yousefi ◽  
Mahdi Khazaei
Keyword(s):  
Residual Stress ◽  
Service Life ◽  
Fatigue Behavior ◽  
Composite Patch ◽  
Mechanically Fastened ◽  
Patch Repairs ◽  
Adhesive Thickness ◽  
Patch Length

In many industries, when replacement of a part is not possible or economic, the repair is done. One of the best methods for repairing metal and composite parts is using composite patches. Repairing with a composite patch is a widespread field to extend the service life of the cracked components. This technique is more structurally efficient with fewer damages on the structure than others. The bonded patch offers many advantages over a mechanically fastened doubler, which include improved fatigue behavior, reduced corrosion, and easy conformance to complex aerodynamic contours. In this article, advantages of the composite patch and its efficiency and durability are discussed, and the most important parameters (patch and adhesive thickness, patch separation, residual stress, patch length and width, etc.) affecting its performance are studied based on the latest available references.

scholarly journals Acoustic emission for monitoring aircraft structures

2009 ◽  
Vol 223 (5) ◽  
pp. 525-532 ◽  
Author(s):  
K M Holford ◽  
R Pullin ◽  
S L Evans ◽  
M J Eaton ◽  
J Hensman ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Magnetic Particle ◽  
Fatigue Cracks ◽  
Principal Component ◽  
Fatigue Loading ◽  
Probability Density Functions ◽  
Aircraft Industry ◽  
Safety And Reliability ◽  
Critical Components

Structural health monitoring (SHM) is of paramount importance in the aircraft industry: not only to ensure the safety and reliability of aircraft in flight and to ensure timely maintenance of critical components, but also increasingly to monitor structures under test for airworthiness certification of new designs. This article highlights some of the recent advances in the acoustic emission (AE) technique as applied to SHM, and the new approaches that are crucial for the successful use of AE data for diagnostic purposes. These include modal analysis, enhanced location techniques, and novel signal processing approaches. A case study is presented on a landing gear component undergoing fatigue loading in which a linear location analysis using conventional techniques identified the position of fracture and final rupture of the specimen. A principal component analysis approach was used to separate noise signals from signals arising from fatigue cracks, which identified and located further fatigue crack positions, subsequently confirmed by magnetic particle inspection. Kernel probability density functions are used to aid visualization of the damage location.

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