Innovative repair of Aerospace Structures with Curing Optimization and Life Cycle Monitoring Abilities

Transcription

1 Innovative repair of Aerospace Structures with Curing Optimization and Life Cycle Monitoring Abilities ACP7-GA A. Paipetis, V. Kostopoulos, I. Harismendy, S. Florez, B. Canflanca Session 6-Improving Cost Efficiency

2 IAPETUS: BACKGROUND The increasing age of the European and world wide aircraft fleet and the introduction of advanced composite materials in aircraft primary structures impose the need for new maintenance methodologies that will secure the airworthiness of ageing aerostructures. According to the findings of the NOESIS project, the introduction of CNT's into the matrix of FRP's leads to an impressive enhancement of material properties (from mechanical to electrical). In an effort to identify applications where these enhanced properties could provide a significant advantage and lead to technological innovations, patch repair was considered. Patch repair is a promising technology but still pose significant challenges with respect to: Repair material system Patch application/curing process In-service performance

3 IAPETUS: Main goal IAPETUS aims at revolutionizing aircraft repair processes with composite materials, (mainly the hot bond repair approach used in field repair) by using novel hybrid composites (doped with CNTs) that will enable to step change the hot bond field repair by: Introducing an innovative curing methodology (either via direct resistance heating or by induction heating) of the patch/adhesive system, with the benefits of homogenous heating and curing and the minimization of the developed thermal stresses. In addition the introduction of an on line curing monitoring system will allow for a precise control of curing concluded to enhanced quality of the resulted repair. Providing direct inspection of the bonding/repair integrity and continuous health monitoring of the repaired site in service. Offering increased mechanical and bonding performance in the repair itself.

4 IAPETUS: CONSORTIUM OVERVIEW Name Country Type Main RTD Role in Iapetus TECNALIA ES RTD Coordinator Material (CNT) development, Laboratory testing, Electrochemical behaviour, numerical analysis, NDT techniques PZL-Swidnik PL IND Manufacturing, Repair application, Testing of large scale components Huntsman Advanced Materials GmbH SW IND Development & supply of materials (resins & adhesives) University of Patras EL HE Technology development, Laboratory testing, Sensing & monitoring technologies, numerical analysis Integrated Aerospace Sciences Corporation (INASCO) EL SME Curing monitoring system development, numerical analysis, Economic evaluation DAHER Aerospace FR IND Manufacturing, Repair application, GMI AERO FR SME Repair equipment, modelling & thermal management of processes University of Ioannina EL HE Technology development, Laboratory testing, Sensing & monitoring technologies University of Sheffield UK HE Laboratory testing, Sensing & monitoring technologies, numerical analysis Hellenic aerospace Industry (HAI) EL IND Manufacturing, Repair application,

5 IAPETUS: WORPLAN SP1: Curing techniques Development of patch material Development of the two innovative curing techniques: Resistance Induction SP2: Sensing System Demonstrate the applicability of the smart patch concept based on the approach of electrical resistance measurements Provide both hardware and software for a real life application of the method SP3: Integration

6 IAPETUS: SCIENTIFIC & TECHNICAL OBJECTIVES Development of innovative, easy to apply, direct heating composite bonding patch repair technology for the maintenance of both aluminium and composite aerostructures. Development of a system with a cure monitoring sensor embedded in the conductive patch, which controls the heating profile to optimally cure the bonding patch repair. Development of new electrically conductive composite repair patches (graphite/ epoxy) with improved mechanical performance based on the modification of the matrix with a controlled amount of Carbon Nanotubes (CNTs). Development of a new generation of resins, modified by using CNT additives that offer improved mechanical properties, increased peeling and shear strength, controlled coefficient of thermal expansion and high electric and thermal conductivity, permitting, thus, the application of the direct heating polymerization processes. Two heating/curing alternatives for the new patch repair system will be investigated: (a) direct resistance heating and (b) induction heating.

7 IAPETUS: SCIENTIFIC & TECHNICAL OBJECTIVES To overcome the problem of galvanic corrosion in the case of aluminium Aerostructures, either by minimizing Red Ox potential through the proper control of CNT types and content, or by overcoming it with the use of modified but electrically non-conductive adhesive films. To develop approaches that exploit the proven sensing properties of the integral CNT network in the patch and the adhesive for the continuous monitoring of the structural integrity of the repaired site. This will be performed via the measurement of the conductivity changes and the mapping of variations that are due to deformation of the percolated CNT network and/ or irreversible changes due to the in service degradation of the patch and the adhesive. To integrate and validate all the above technologies for the innovative repair and the smart patch for damage monitoring in coupon level. To implement the above technologies for the repair of small scale, wing like aluminium and composite aerostructures using innovative curing technologies and achieve enhanced damage tolerance and fatigue performance smart patch repair, with life monitoring capabilities.

8 SUMMARY OF MAIN ACHIEVEMENTS OF IAPETUS SO FAR SP1 (Innovative curing methodologies) Identification of all the requirements with regard to the aeronautical repair process: patch, application process and quality control procedure. Implementation of an efficient CNT dispersion protocol (based in the resulting electrical conductivity) in a two component certified repair epoxy system (Epocast 52 A/B) and patch fabrication technique for its incorporation in the composite patch laminates. Investigation of the electrochemical (galvanic) corrosion phenomena associated with the application of conductive composite materials on metal (mainly aluminium) structures in the presence of CNTs. The concept has been successfully proved with other material systems but still development effort is required in order to understand the mechanism in high engineering repair systems.

9 SUMMARY OF MAIN ACHIEVEMENTS OF IAPETUS SO FAR SP1 (Innovative curing methodologies) Successful lab scale implementation of resistance heating set up and investigation of the role of CNT additives. First indications of improved mechanical properties. Development and optimization of a portable induction heating set-up for the curing of CFRP patches on metal and composites substrates and investigation of the role of CNT additives

10 SUMMARY OF MAIN ACHIEVEMENTS OF IAPETUS SO FAR SP1 (Innovative curing methodologies) Deployment of a curing monitoring system based on thin film dielectric sensors adapted to CNT enhanced materials and patch application process. Effects of CNTs in the curing were observed. Modelling schemes that attempt to simulate the evolution of temperature throughout the resistance curing process have been developed

11 SUMMARY OF MAIN ACHIEVEMENTS OF IAPETUS SO FAR SP2 (Innovative smart composite patches for damage detection in repair ) C-scan images for aluminium substrate as captured from Gate 1.Configuration 3 (b) Configuration 4 Thermographic camera set-up -. Phase images by lock-in thermography. (a) Al substrate, (b) Composite substrate

12 SUMMARY OF MAIN ACHIEVEMENTS OF IAPETUS SO FAR SP2 (Innovative smart composite patches for damage detection in repair ) 1 between 1-2 Oh m io 0,18 0,16 0,14 0,12 0,1 0,08 0,06 0,04 0, Electrodo number

13 IAPETUS- On going research SP1: Induction: Continue investigations and trials. Resistance: Further optimisation of the resistance heating parameters (electrodes sizes, placement, etc.) and implementation of an automatic control system. SP2: Conclude on the off-line technique for QA aspects. Inplementation of a commom realisation platforfm (ERM+thermography) for on-line application. SP3: Integration of the technologies of innovative curing, curing control and monitoring and the smart patch technologies First step: Integration of technologies in small scale components and validation through appropriate testing (quasi-static and dynamic/fatigue loading conditions). Validation of the integrated system in a suitable aeronautical structure.

14 Acknowledgment to: IAPETUS team for their strong effort Project Officer Mr. Pablo Pérez Illana for his support. Questions?