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Jung-ju Lee - One of the best experts on this subject based on the ideXlab platform.

  • Fatigue Crack Growth Monitoring by Optical Fiber Sensors in Smart Composite Patch Repairs
    Key Engineering Materials, 2006
    Co-Authors: Dae-cheol Seo, Jung-ju Lee
    Abstract:

    The fiber optic smart structures allow engineers to add nerve systems to their designs, giving structures capabilities that would be very difficult to achieve by other means, including continuous assessment of damage processes. In this study, we evaluated the potentiality of the application of the optical fiber sensors to the monitoring of the fatigue crack growth behavior of Composite Patch repaired structures. The Composite Patch with embedded optical fiber sensors can be considered as a smart Patch which has both repairing and monitoring functions. We used recently developed Transmission-type Extrinsic Fabry-Perot Interferometric (TEFPI) optical fiber sensors for the monitoring of fatigue crack growth behavior of cracked thick aluminum plate repaired with bonded Composite Patch. The sensing principle and the senor construction of the optical fiber sensor are presented. The experimental results show that it is possible to monitor the fatigue crack growth behavior of structures repaired with Composite Patch using the optical fiber sensor

  • monitoring of fatigue crack growth of cracked thick aluminum plate repaired with a bonded Composite Patch using transmission type extrinsic fabry perot interferometric optical fiber sensors
    Smart Materials and Structures, 2002
    Co-Authors: Dae-cheol Seo, Jung-ju Lee, Ilbum Kwon
    Abstract:

    Recently, optical fiber sensors have been increasingly applied to monitor various engineering and civil structural components. These fiber optic smart structures allow engineers to add nervous systems to their designs, giving structures capabilities that would be very difficult to achieve by other means, including continuous assessment of damage processes. Several studies associated with crack monitoring using optical fiber sensors have been reported. In this study, we used recently developed transmission-type extrinsic Fabry–Perot interferometric (TEFPI) optical fiber sensors for the monitoring of fatigue crack growth behavior of cracked thick aluminum plate repaired with a bonded Composite Patch. The TEFPI optical fiber sensor has both the advantages of reflection-type EFPI optical fiber sensors and a simpler and more effective function to distinguish strain direction than do reflection-type EFPI optical fiber sensors. The objective of this study is to evaluate the potentiality of the application of TEFPI optical fiber sensors to the monitoring of the fatigue crack growth behavior of Composite Patch repaired structures. The sensing principle and the sensor construction of the TEFPI optical fiber sensor are presented. The experimental results from fatigue tests of center cracked tension aluminum specimens repaired with a bonded Composite Patch are presented and discussed. TEFPI optical fiber sensors are embedded and surface bonded to the Composite Patch at several locations. The experimental results show that it is possible to monitor the fatigue crack growth behavior of Composite Patch repaired structures using TEFPI optical fiber sensors.

  • fatigue crack growth behavior of cracked aluminum plate repaired with Composite Patch
    Composite Structures, 2002
    Co-Authors: Dae-cheol Seo, Jung-ju Lee
    Abstract:

    Abstract In this study, we investigated the fatigue crack growth behavior of cracked aluminum plate repaired with bonded Composite Patch especially in thick plate. Adhesively bonded Composite Patch repair technique has been successfully applied to military aircraft repair and expanded its application to commercial aircraft industry recently. Also this technique has been expanded its application to the repair of load bearing primary structure from secondary structure repair. Therefore, a through understanding of crack growth behavior of thick panel repaired with bonded Composite Patch is needed. We investigated the fatigue crack growth behavior of thick panel repaired with bonded Composite Patch using the stress intensity factor range ( ΔK ) and fatigue crack growth rate (d a /d N ). The stress intensity factor of Patched crack was determined from experimental result by comparing the crack growth behavior of specimens with and without repair. Also, by considering the three-dimensional (3D) stress state of Patch crack, 3D finite element analyses were performed to obtain the stress intensity factor of crack repaired by bonded Composite Patch. Two types of crack front modeling, i.e. uniform crack front model and skew crack front model, were used. The stress intensity factor calculated using FEM was compared with the experimentally determined values.

Dae-cheol Seo - One of the best experts on this subject based on the ideXlab platform.

  • Fatigue Crack Growth Monitoring by Optical Fiber Sensors in Smart Composite Patch Repairs
    Key Engineering Materials, 2006
    Co-Authors: Dae-cheol Seo, Jung-ju Lee
    Abstract:

    The fiber optic smart structures allow engineers to add nerve systems to their designs, giving structures capabilities that would be very difficult to achieve by other means, including continuous assessment of damage processes. In this study, we evaluated the potentiality of the application of the optical fiber sensors to the monitoring of the fatigue crack growth behavior of Composite Patch repaired structures. The Composite Patch with embedded optical fiber sensors can be considered as a smart Patch which has both repairing and monitoring functions. We used recently developed Transmission-type Extrinsic Fabry-Perot Interferometric (TEFPI) optical fiber sensors for the monitoring of fatigue crack growth behavior of cracked thick aluminum plate repaired with bonded Composite Patch. The sensing principle and the senor construction of the optical fiber sensor are presented. The experimental results show that it is possible to monitor the fatigue crack growth behavior of structures repaired with Composite Patch using the optical fiber sensor

  • monitoring of fatigue crack growth of cracked thick aluminum plate repaired with a bonded Composite Patch using transmission type extrinsic fabry perot interferometric optical fiber sensors
    Smart Materials and Structures, 2002
    Co-Authors: Dae-cheol Seo, Jung-ju Lee, Ilbum Kwon
    Abstract:

    Recently, optical fiber sensors have been increasingly applied to monitor various engineering and civil structural components. These fiber optic smart structures allow engineers to add nervous systems to their designs, giving structures capabilities that would be very difficult to achieve by other means, including continuous assessment of damage processes. Several studies associated with crack monitoring using optical fiber sensors have been reported. In this study, we used recently developed transmission-type extrinsic Fabry–Perot interferometric (TEFPI) optical fiber sensors for the monitoring of fatigue crack growth behavior of cracked thick aluminum plate repaired with a bonded Composite Patch. The TEFPI optical fiber sensor has both the advantages of reflection-type EFPI optical fiber sensors and a simpler and more effective function to distinguish strain direction than do reflection-type EFPI optical fiber sensors. The objective of this study is to evaluate the potentiality of the application of TEFPI optical fiber sensors to the monitoring of the fatigue crack growth behavior of Composite Patch repaired structures. The sensing principle and the sensor construction of the TEFPI optical fiber sensor are presented. The experimental results from fatigue tests of center cracked tension aluminum specimens repaired with a bonded Composite Patch are presented and discussed. TEFPI optical fiber sensors are embedded and surface bonded to the Composite Patch at several locations. The experimental results show that it is possible to monitor the fatigue crack growth behavior of Composite Patch repaired structures using TEFPI optical fiber sensors.

  • fatigue crack growth behavior of cracked aluminum plate repaired with Composite Patch
    Composite Structures, 2002
    Co-Authors: Dae-cheol Seo, Jung-ju Lee
    Abstract:

    Abstract In this study, we investigated the fatigue crack growth behavior of cracked aluminum plate repaired with bonded Composite Patch especially in thick plate. Adhesively bonded Composite Patch repair technique has been successfully applied to military aircraft repair and expanded its application to commercial aircraft industry recently. Also this technique has been expanded its application to the repair of load bearing primary structure from secondary structure repair. Therefore, a through understanding of crack growth behavior of thick panel repaired with bonded Composite Patch is needed. We investigated the fatigue crack growth behavior of thick panel repaired with bonded Composite Patch using the stress intensity factor range ( ΔK ) and fatigue crack growth rate (d a /d N ). The stress intensity factor of Patched crack was determined from experimental result by comparing the crack growth behavior of specimens with and without repair. Also, by considering the three-dimensional (3D) stress state of Patch crack, 3D finite element analyses were performed to obtain the stress intensity factor of crack repaired by bonded Composite Patch. Two types of crack front modeling, i.e. uniform crack front model and skew crack front model, were used. The stress intensity factor calculated using FEM was compared with the experimentally determined values.

M Belhouari - One of the best experts on this subject based on the ideXlab platform.

Sabine Mall - One of the best experts on this subject based on the ideXlab platform.

  • modeling and validation of Composite Patch repair to cracked thick and thin metallic panels
    Composites Part A-applied Science and Manufacturing, 2009
    Co-Authors: Sabine Mall, D S Conley
    Abstract:

    A two-dimensional finite element analysis is presented to predict crack growth behavior of cracked panels repaired with bonded Composite Patch. Fatigue experiments were conducted with precracked aluminum specimens of two thicknesses (1 and 6.35 mm), with and without debond, and repaired asymmetrically. Fatigue lives of thick and thin repaired panels extended four and ten times relative to unrepaired cases, respectively. The predicted fatigue crack growth rates were in agreement with experimental values at the unPatched face but not at the Patched face. Thus, the present analysis provides a conservative assessment of durability and damage tolerance of repaired thin and thick panels.

  • fatigue crack growth analysis of stiffened cracked panel repaired with bonded Composite Patch
    Engineering Fracture Mechanics, 2006
    Co-Authors: V Sabelkin, Sabine Mall, J B Avram
    Abstract:

    Abstract Fatigue crack growth behavior in a stiffened thin 2024-T3 aluminum panel repaired with one-sided adhesively bonded Composite Patch was investigated through experiments and analyses. The Patch had three plies of unidirectional boron/epoxy Composite. 2024-T3 aluminum stiffeners were riveted as well as bonded on the panel. Stiffeners were oriented in the loading direction and were spaced at either 102 mm or 152 mm with a crack centered between them. Also, un-repaired cracked panel with and without stiffeners were studied. Experiment involved tension–tension fatigue at constant amplitude with maximum stress of 120 MPa and stress ratio of 0.05. Bonded Composite Patch repair increased fatigue life about five-fold in the case of stiffened panels while it increased about ten fold in the case of un-stiffened panels. Fatigue life also increased with decrease of the distance between the stiffeners for both repaired and un-repaired panels. A three-dimensional finite element method was used to analyze the experiments. Residual thermal stresses, developed during Patch bonding, requires the knowledge of temperature at which adhesive becomes effective in creating a bond between the structure and Patch in the analysis. A simple method to estimate the effective curing temperature range is suggested in this study. The computed stress intensity factor versus measured crack growth relationships for all panel configurations were consistent and in agreement with the counterpart from the test material. Thus, the present approach provides a means to analyze the fatigue crack growth behavior of stiffened structures repaired with adhesively bonded Composite Patch.

  • Nonlinear analysis of bonded Composite Patch repair of cracked aluminum panels
    Composite Structures, 1998
    Co-Authors: Sam Naboulsi, Sabine Mall
    Abstract:

    Analyses of adhesively bonded Composite Patches to repair cracked structures have been the focus of many studies. Most of these studies investigated the damage tolerance of the repaired structure by using linear analysis. This study involves nonlinear analysis of the adhesively bonded Composite Patch to investigate its effects on the damage tolerance of the repaired structure. The nonlinear analysis utilizes the three-layer technique which includes geometric nonlinearity to account for large displacements of the repaired structure and also material nonlinearity of the adhesive. The three-layer technique uses two-dimensional finite element analysis with Mindlin plate elements to model the cracked plate, adhesive and Composite Patch. The effects of geometric nonlinearity on the damage tolerance of the cracked plate is investigated by computing the stress intensity factor and fatigue growth rate of the crack in the plate. The adhesive is modeled as a nonlinear material to characterize debond behavior. The elastic-plastic analysis of the adhesive utilizes the extended Drucker-Prager model. A detailed discussion on the effects of nonlinear analysis for a bonded Composite Patch repair of a cracked aluminum panel is presented in this paper.

Shankar Mall - One of the best experts on this subject based on the ideXlab platform.

  • modeling of cracked thick metallic structure with bonded Composite Patch repair using three layer technique
    Composite Structures, 1999
    Co-Authors: J J Schubbe, Shankar Mall
    Abstract:

    A finite element analysis involving three-layers of two-dimensional Mindlin plate elements, to model cracked plate, adhesive, and Composite Patch, was developed to characterize fatigue crack growth behavior of a thick metallic panel repaired with an adhesively bonded Composite Patch. Also, fatigue experiments were conducted with 6.35 mm thick specimens with a pre-crack repaired asymmetrically with adhesively bonded unidirectional boron/epoxy Patch. Fatigue crack growth rates on the unPatched and Patched faces (PF) were measured along with debond of the Composite Patch. Stress intensity factors obtained from the analysis were combined with the fatigue crack growth relationship for the unrepaired cracked material to obtain the analytical fatigue crack growth rates. The experimental and analytical fatigue crack growth rates on the unPatched face (UPF) were in a good agreement with each other when the proper consideration of the effective crack length and debond were incorporated in the analysis. Thus, the three-layer technique was found to be capable of characterizing the fatigue crack growth behavior of the repaired thick panels as in the case of repaired thin panels shown in the previous studies.

  • Methodology to analyse aerospace structures repaired with a bonded Composite Patch
    The Journal of Strain Analysis for Engineering Design, 1999
    Co-Authors: Sam Naboulsi, Shankar Mall
    Abstract:

    AbstractAdhesively bonded Composite repair of metallic structures is one of the candidate technologies that has enormous potential in the ageing aircraft. A computational tool to analyse the repaired aerospace structure using an adhesively bonded Composite Patch is presented. This involves the three-layer technique based on the two-dimensional finite element method for adhesively bonded Composite Patch repair of cracked structures. This technique is capable of characterizing the crack growth and debond growth behaviour, as well as predicting the fatigue life extension of the repaired structure with a perfectly or imperfectly bonded Patch. Also, the thermal effects which may develop during bonding or during service and the non-linear material behaviour of the adhesive are incorporated in this technique. The results from the three-layer technique show good agreement with experimental results as well as a previous investigator's published numerical results. Besides the accuracy of the technique, the advantag...

  • Characterization of fatigue crack growth in aluminium panels with a bonded Composite Patch
    Composite Structures, 1997
    Co-Authors: Sam Naboulsi, Shankar Mall
    Abstract:

    This study introduces an analytical procedure to characterize the fatigue crack growth behavior in an aluminium panel repaired with a bonded Composite Patch. This procedure involves the computation of the stress intensity factor from a two-dimensional finite element method consisting of three layers to model cracked plate, adhesive and Composite Patch. In this three layer finite element analysis, as recently introduced by the authors, two-dimensional Mindlin plate elements with transverse shear deformation capability are used. The computed stress intensity factor is then compared with the experimental counterpart. The latter was obtained from the measured fatigue crack growth rate of an aluminium panel with a bonded Patch by using the power law relationship (Paris Law) of an unPatched aluminum panel. Both a completely bonded Patch (with no debond) and a partially bonded Patch (with debond) are investigated in this study. This procedure, thus, provides an effective and reliable technique to predict the fatigue life of a repaired structure with a bonded Patch, or alternatively, it can be used to design the bonded Composite Patch configuration to enhance the fatigue life of cracked structure.

  • Modeling of a cracked metallic structure with bonded Composite Patch using the three layer technique
    Composite Structures, 1996
    Co-Authors: Sam Naboulsi, Shankar Mall
    Abstract:

    Abstract Due to the high computational cost of three-dimensional finite element analysis, the two-dimensional finite element analysis involving the three layer technique is introduced to investigate the repair of cracked metallic structures using an adhesively bonded Composite Patch. In the three layer technique, two-dimensional Mindlin plate elements with transverse shear deformation capability are used for all three layers; cracked plate, adhesive and Composite Patch. The accuracy of the three layer technique to compute the stress intensity factor for the metallic crack is demonstrated by a comparison with available two- and three-dimensional models. The strain energy release rates of the debond at the adhesive interfaces are also examined and compared with the previous studies. The three layer technique provides an efficient and accurate alternative model which is capable of investigating in depth the adhesive effects on the bonded Patch repair of cracked metallic structures.