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

  • development of a proof test for through life monitoring of bond integrity in adhesively bonded repairs to Aircraft Structure
    International Journal of Adhesion and Adhesives, 2012
    Co-Authors: A A Baker, D Bitton, John Wang
    Abstract:

    Abstract This paper describes the development of a proof test to evaluate the through-life integrity of structural adhesive bonds. The test is focussed on adhesively bonded patch repairs for Aircraft Structure; especially those where flight safety depends on the integrity of the repair patch. The test could be used either as an alternative or as an addition to structural health monitoring of bonded repairs to increase confidence to the extent that they could be certified for application to flight-critical Structure. The implementation of the test is as follows: thin coupons of the patch material are bonded to the surface of the parent Structure simultaneously with, and therefore under very similar conditions to the repair patch. These coupons are proof tested periodically in shear using a torque wrench. Failure of the coupon below a predetermined proof load provides an indication that the adhesive bond to the patch or (possibly) the patch itself has degraded and should be replaced. It was concluded that this test is a very promising cost-effective approach for detecting defective or deteriorated adhesive bonds; however, to raise the technology readiness level to the extent that it could be considered for Aircraft applications more work is required to improve the test database and increase practicality.

  • micrographic studies on adhesively bonded scarf repairs to thick composite Aircraft Structure
    Composites Part A-applied Science and Manufacturing, 2009
    Co-Authors: A A Baker, B Whittingham, A Harman, D Bitton
    Abstract:

    Abstract The hard-patch approach to scarf repairs involves adhesively bonding a pre-formed patch into the scarf cavity. This approach has several potential advantages compared with the conventional soft-patch approach, which involves forming the patch from pre-preg and co-bonding it with the adhesive during cure of the patch directly in the repair cavity. Two methods for producing the hard-patch were investigated. The first was the moulded approach where the patch was laid up in a mould and cured prior to bonding in the repair cavity. The development and implementation of the moulded hard-patch repair technique on an F/A-18 horizontal stabiliser is described. The second approach involves machining the patch from a composite panel using digitised data obtained from the use of surface profiling equipment to capture the scarf cavity surface. Micrographic techniques were used to assess critical features of the bond-line produced from the different techniques. The results are compared with microscopic studies from a second F/A-18 horizontal stabiliser that was repaired much earlier using the soft-patch approach. Each repair is assessed in terms of the consolidation of plies along the bond-line and the conformity of the patch to the repair cavity as well as adhesive uniformity and porosity.

  • bonded composite repair of fatigue cracked primary Aircraft Structure
    Composite Structures, 1999
    Co-Authors: A A Baker
    Abstract:

    Abstract Repairs based on adhesively bonded fibre-composite patches or reinforcements are more structurally efficient and much less damaging to the parent Structure than standard repairs based on mechanically fastened metallic patches. As a result of the high reinforcing efficiency of bonded patches “live” fatigue cracks can be successfully repaired. However, when such repairs are applied to primary Structure a conservative certification approach is often taken in which no credit is given to the patch system for slowing crack growth or restoring residual strength. Thus, cracks approaching critical size cannot be repaired and inspection intervals must be based on the predicted growth behaviour of the unpatched crack. To allow credit to be given to the patch the need is to demonstrate either (a) that the likelihood of patch loss is acceptably low or (b) that its loss can be immediately detected. Two approaches are discussed: the first approach which addresses (a) is based on a demonstrated ability to predict the patch system’s fatigue behaviour and to assure its environmental durability. The second approach that addresses (b) is based on the “smart patch” concept in which the patch system monitors its own health.

D Bitton - One of the best experts on this subject based on the ideXlab platform.

  • development of a proof test for through life monitoring of bond integrity in adhesively bonded repairs to Aircraft Structure
    International Journal of Adhesion and Adhesives, 2012
    Co-Authors: A A Baker, D Bitton, John Wang
    Abstract:

    Abstract This paper describes the development of a proof test to evaluate the through-life integrity of structural adhesive bonds. The test is focussed on adhesively bonded patch repairs for Aircraft Structure; especially those where flight safety depends on the integrity of the repair patch. The test could be used either as an alternative or as an addition to structural health monitoring of bonded repairs to increase confidence to the extent that they could be certified for application to flight-critical Structure. The implementation of the test is as follows: thin coupons of the patch material are bonded to the surface of the parent Structure simultaneously with, and therefore under very similar conditions to the repair patch. These coupons are proof tested periodically in shear using a torque wrench. Failure of the coupon below a predetermined proof load provides an indication that the adhesive bond to the patch or (possibly) the patch itself has degraded and should be replaced. It was concluded that this test is a very promising cost-effective approach for detecting defective or deteriorated adhesive bonds; however, to raise the technology readiness level to the extent that it could be considered for Aircraft applications more work is required to improve the test database and increase practicality.

  • micrographic studies on adhesively bonded scarf repairs to thick composite Aircraft Structure
    Composites Part A-applied Science and Manufacturing, 2009
    Co-Authors: A A Baker, B Whittingham, A Harman, D Bitton
    Abstract:

    Abstract The hard-patch approach to scarf repairs involves adhesively bonding a pre-formed patch into the scarf cavity. This approach has several potential advantages compared with the conventional soft-patch approach, which involves forming the patch from pre-preg and co-bonding it with the adhesive during cure of the patch directly in the repair cavity. Two methods for producing the hard-patch were investigated. The first was the moulded approach where the patch was laid up in a mould and cured prior to bonding in the repair cavity. The development and implementation of the moulded hard-patch repair technique on an F/A-18 horizontal stabiliser is described. The second approach involves machining the patch from a composite panel using digitised data obtained from the use of surface profiling equipment to capture the scarf cavity surface. Micrographic techniques were used to assess critical features of the bond-line produced from the different techniques. The results are compared with microscopic studies from a second F/A-18 horizontal stabiliser that was repaired much earlier using the soft-patch approach. Each repair is assessed in terms of the consolidation of plies along the bond-line and the conformity of the patch to the repair cavity as well as adhesive uniformity and porosity.

George Vachtsevanos - One of the best experts on this subject based on the ideXlab platform.

  • A Novel Linear Polarization Resistance Corrosion Sensing Methodology for Aircraft Structure
    2015
    Co-Authors: Richard J Connolly, Vinod S. Agarwala, Ernard Laskowski, Margare Garva, George Vachtsevanos
    Abstract:

    A direct method of measuring corrosion on a Structure us-ing a micro-linear polarization resistance (µLPR) sensor is presented. The new three-electrode µLPR sensor design pre-sented in this paper improves on existing LPR sensor tech-nology by using the Structure as part of the sensor system, allowing the sensor electrodes to be made from a corro-sion resistant or inert metal. This is in contrast to a two-electrode µLPR sensor where the electrodes are made from the same material as the Structure. A controlled experiment, conducted using an ASTM B117 salt fog, demonstrated the three-electrode µLPR sensors have a longer lifetime and bet-ter performance when compared to the two-electrode µLPR sensors. Following this evaluation, a controlled experiment using the ASTM G85 Annex 5 standard was performed to evaluate the accuracy and precision of the three-electrode µLPR sensor when placed between lap joint specimens made from AA7075-T6. The corrosion computed from the µLPR sensors agreed with the coupon mass loss to within a 95% confidence interval. Following the experiment, the surface morphology of each lap joint was determined using laser mi-croscopy and stylus-based profilometry to obtain local and global surface images of the test panels. Image processing, feature extraction, and selection tools were then employed to identify the corrosion mechanism (e.g. pitting, intergranular). Douglas Brown et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 United States License, which permits unrestricted use, distribution, and reproduction in any medium, pro-vided the original author and source are credited. 1

  • a novel linear polarization resistance corrosion sensing methodology for Aircraft Structure
    2014
    Co-Authors: Douglas W Brown, Richard J Connolly, Margaret R Garvan, Honglei Li, Vinod S. Agarwala, George Vachtsevanos
    Abstract:

    Abstract : A direct method of measuring corrosion on a Structure using a micro-linear polarization resistance (LPR) sensor is presented. The new three-electrode LPR sensor design presented in this paper improves on existing LPR sensor technology by using the Structure as part of the sensor system, allowing the sensor electrodes to be made from a corrosion resistant or inert metal. This is in contrast to a two electrode LPR sensor where the electrodes are made from the same material as the Structure. A controlled experiment,conducted using an ASTM B117 salt fog, demonstrated the three-electrode LPR sensors have a longer lifetime and better performance when compared to the two-electrode LPR sensors. Following this evaluation, a controlled experiment using the ASTM G85 Annex 5 standard was performed to evaluate the accuracy and precision of the three-electrode LPR sensor when placed between lap joint specimens made from AA7075-T6. The corrosion computed from the LPR sensors agreed with the coupon mass loss to within a 95%confidence interval. Following the experiment, the surface morphology of each lap joint was determined using laser microscopy and stylus-based profilometry to obtain local and global surface images of the test panels. Image processing, feature extraction, and selection tools were then employed to identify the corrosion mechanism (e.g. pitting, intergranular).

B Whittingham - One of the best experts on this subject based on the ideXlab platform.

  • micrographic studies on adhesively bonded scarf repairs to thick composite Aircraft Structure
    Composites Part A-applied Science and Manufacturing, 2009
    Co-Authors: A A Baker, B Whittingham, A Harman, D Bitton
    Abstract:

    Abstract The hard-patch approach to scarf repairs involves adhesively bonding a pre-formed patch into the scarf cavity. This approach has several potential advantages compared with the conventional soft-patch approach, which involves forming the patch from pre-preg and co-bonding it with the adhesive during cure of the patch directly in the repair cavity. Two methods for producing the hard-patch were investigated. The first was the moulded approach where the patch was laid up in a mould and cured prior to bonding in the repair cavity. The development and implementation of the moulded hard-patch repair technique on an F/A-18 horizontal stabiliser is described. The second approach involves machining the patch from a composite panel using digitised data obtained from the use of surface profiling equipment to capture the scarf cavity surface. Micrographic techniques were used to assess critical features of the bond-line produced from the different techniques. The results are compared with microscopic studies from a second F/A-18 horizontal stabiliser that was repaired much earlier using the soft-patch approach. Each repair is assessed in terms of the consolidation of plies along the bond-line and the conformity of the patch to the repair cavity as well as adhesive uniformity and porosity.

Robert Hannum - One of the best experts on this subject based on the ideXlab platform.

  • a real time active smart patch system for monitoring the integrity of bonded repair on an Aircraft Structure
    Smart Materials and Structures, 2006
    Co-Authors: Xinlin Qing, Shawn J Beard, Amrita Kumar, Robert Hannum
    Abstract:

    There currently exists a need to develop a cost-effective, in-service structural health monitoring (SHM) system for determining the initial quality of a bonded repair and assessing the long-term durability of the bonded repair on an Aircraft Structure. In this paper, a real-time active smart patch system (SPS) based on SMART layer technology is introduced for monitoring the integrity of bonded repairs. First, an overview of the SPS is given for typical metal and composite repairs. To illustrate the capability of the SPS, three applications are presented: (1) monitoring of the cure progress of the bonded repair adhesive, (2) detection of the initial artificial disbond between the composite patch and the metal Structure, and (3) monitoring of damage in and around a bonded repair during fatigue cycling. The results show that, through the use of a real-time active SPS approach of using sensors placed in, on or around the repair, the initial quality and long-term durability of the repair can be evaluated and monitored.