Final Report Summary - CONDUCTOR (Flexible Conductive Composite Repair Heaters)
Executive Summary:
Appropriate curing of the patch resin and the adhesive layer is an essential step to secure the integrity and the sound mechanical performance of a bonded composite repair. Today, the required elevation of temperature is usually achieved by means of a resistance heating blanket, which conduct heat to the repair area, regulated through closed loop temperature control, using spot temperature measurements. Heating Blankets for Composite Repair are presently designed by GMI Aero to fullfil a large range of cases in terms of geometry, shapes and temperature levels. The techniques of fabrication is based on encapsulating NiCr wires between two silicone sheets to ensure electrical isolation.on routing NiCr wires on silicone sheet. The encapsulation between two silicone layers assure electrical isolation. Even if this method is rather «simple» and allows to offer products that present excellent performances, technicians of MROs and Airlines are always frustrated not to have the possibility to manufacture in the field a product that can be tailored to the dimensions of the patch. The answer to such request is the Conductor Technology, which has been jointly developed by GMI and NTUA, within the frame of Cleansky. With this innovation, the quality of bonding operations will be improved and productivity will be increased by totally suppressing the lead time for heating element fabrication. The product will appear for the user as a standard silicone blanket that integrates a mesh of specially coated fibers. These fibers conduct electrical power in a distributed way over the whole surface of the blanket thus gaining in homogeneity. Furthermore, the special weaving of the fibers allows for cutting the blanket in different shapes whenever there is the need to follow contours that inhibit the use of a standard rectangular heating blanket. Power wires installed at pre-defined spots allow easy connection for power supply.The connectors for the power delivery wires have been specially selected to be easily mounted with maximum safety. Main Benefits for the end-user: a) This innovation delivers to the final user the benefits of having a “customised for the application” heating blanket manufactured in place, rather than having to order a special circuit, resulting in the total suppression of lead time for the procurement of heating blankets, b) High versatility in the design of geometrical patterns ; the user is able to adapt the shape of the blanket to a special geometry in order to distribute heat where it is strictly necessary, thus improving the heat management process. Conductor is the answer, in the context of repairing new advanced composite structures, to the search for tailored-made heating blankets adapted to the Thermal signature of the part, c) The fitting to the geometry of the repair area leads to the minimization of risk to overheat areas outside the repair zone, d) Prepared blankets could be further cut in smaller shapes if required, e) High homogeneity in temperature. The heating circuit develops heat with high quality of homogeneity in terms of temperature distribution, f) Conductor is compatible with the existing GMI Aero family of bonding consoles for temperature and power control, g) The Conductor technology allows also to apply for Multi Zone Heating solution (several blankets to cover a large area) and thus can be implemented with existing GMI-Anita Bonding with 2, 4, 6 zones,...
Project Context and Objectives:
The main concept driving the CONDUCTOR project is to apply the CSH principle for the development of special heating equipment and associated methodology that will constitute the basis of a next generation bonding repair equipment, to perform high quality, efficient and cost effective repair curing. This will lead to an environmentally friendly, low-energy, low-cost and easily interfaced solution for a future operational field bonding equipment, that will achieve better repair quality through minimization of temperature inhomogeneity problems.
Consequently the main objectives of this proposal, through the application of the CSH principle for the development of special heating equipment and associated methodology would be:
a. Achievement of more homogeneous temperature distribution within repair areas, leading to improvement of composite repairs quality.
b. Increase of overall repair process robustness, through minimization of elements (cables etc.) exiting vacuum bagging and easier adaptation to 3D geometries.
c. Reduction of overall power requirements, as the area to be heated and the overall thermal losses will be significantly lower compared to conventional heating methods.
d. Increase of repair speed, through:
i) Shortening of time to prepare vacuum bag, given the reduction of cabling.
ii) Possibility to perform steeper temperature increase, if required, given the energy excess provided by the CSH method.
e. Reduction of overall repair costs, due to the factors mentioned above.
Increase of range of applicability of bonded composite repairs, by ensuring the reliable achievement of specified temperature homogeneity requirements for more complex repair cases, as well as for composite to metal repairs
For the achievement of the above mentioned objectives, there were 4 technical Work packages in order to perform the research, development and testing activities of this project:
WP1 contains the definition of the main design parameters and repair process constraints that need to be taken into consideration for the preparation of the specifications and the overall design of the new CSH system, leading to a Preliminary Design Review (PDR). As a result, the overall design specifications of the new equipment will be concluded in this WP. A detailed thermal mapping using numerical simulation will be performed, in order to couple CSH to the developed temperature field and specify the foil configuration requirements. Finally, the first prototype of the PS&CU will be developed and the appropriate CSH foils will be selected.
Within WP2, the CSH device optimisation activities will be performed in order to achieve the set specifications. Moreover, within this WP the appropriate software will be developed, in order to tailor the system performance to the actual application requirements. The outcome of this Task will be an optimized prototype, the specifications of which will be frozen during the Critical Design Review (CDR) to be performed during the final steps of this WP.
In WP3, the first part of the testing of the developed CSH curing tool will take place, in cooperation with the Topic Manager. A reliability and robustness study will be prepared and will be verified against practical results, in order to evaluate the overall performance and robustness of the method. The outcome of this WP, will assist in the preparation of an upgraded CSH heating device to be further tested on curved CFRP structures.
In WP4, the second part of the testing of the developed CSH curing tool will take place on curved CFRP structures, in cooperation with the Topic Manager. A reliability and robustness study will be prepared and will be verified against practical results, in order to evaluate the overall performance and robustness of the method. Moreover, within this WP the overall CSH methodology will be structured, to permit direct application of the developed equipment by the ECO ITD.
Project Results:
Within WP1, the definition of the main design parameters and repair process constraints that need to be taken into consideration for the preparation of the specifications and the overall design of the new CSH (Conductive Skin Heating) system have been specified, as listed in this Deliverable. It is well understood that, given the R&D nature of the project, potential changes to these requirements may be performed during the evolution of this project, as required, after discussion and agreement among involved entities. Moreover, an extensive comparative evaluation study has been performed in order to select the CSH foils material to be used will this project, complying to the requirements set out in Deliverable 1.1. For this reason, several types of carbon veil (foils) have been identified by the Consortium as candidate CSH element, together with metallic foils and expanded metallic foils. It has been decided that two (2) materials comply with most of the project requirements, exhibiting corresponding advantages/disadvantages (Nickel Coated Carbon veil & expanded stainless steel foil). As, it was not evident which of these two materials will be most appropriate for fulfilling the CONDUCTOR objectives, it has been decided to proceed with both materials to the following steps of this project. Within WP2, the optimized prototype of the CSH hardware has started being prepared, including all elements (power supply, flexible foils, connecting parts, conductors etc.) following extensive laboratory tests which was performed on the first prototype equipment. The main application of this prototype equipment will be to optimize the CSH parameters and fine tune accordingly the heating control algorithm, as described in the following Task. The outcome of this Task was an optimized prototype of all equipment developed, the specifications of which was frozen during the Critical Design Review (CDR). Within WP3 the first part of the testing of the developed CSH curing tool took place, in cooperation with the Topic Manager. A reliability and robustness study was prepared and verified against practical results, in order to evaluate the overall performance and robustness of the materials developed and of the methodology used. This Task involved extensive field testing of the developed CSH curing tool equipment and associated equipment and methodology (vacuum bagging specificities, installation requirements, temperature measurement strategy and thermocouple placement guidelines, connectors etc.) for CSH of flat bonded composite repairs. In order to guarantee that all practical application parameters have been taken into consideration, this work was carried out on panels that the Topic Manager has provided and was also demonstrated at the Topic Manager’s facilities. Within WP4 the second part of the testing of the developed CSH curing tool took place. The main goal of this task was to verify the capability of the CSH blanket to operate on curved surfaces. By taking into account all the lesson learned in WP 3, the equipment was improved in areas such as the control software and the blanket production techniques. On the second step, a complicated aircraft part with medium radiuses was selected as a representative structure to test the limits of the new blankets application and also demonstrate its abilities. As a conclusion, the work performed within the project has generally been in line with the provisions of the Dow, while additional elements and effort has been added, as analyzed previously. The CONDUCTOR project has been delayed by approximately nine (9) months and therefore, a request for the extension of the CONDUCTOR project has been submitted and was approved by CSJU, with a new finishing date of 31/8/2014. No other contractual and / or financial provisions were affected, whatsoever.
Potential Impact:
Replying directly to JTI CfP, the primary drivers for CONDUCTOR relate to safety, economic and societal issues. The application of the proposed advantages to the composite repair process will improve reliability during operation, improve performance and minimise the time the aircraft needs to spend on the ground for repair, which are among the main targets of the CleanSky JTI. This will permit increased aircraft availability and lower maintenance costs to be incurred by the operating companies. Savings Generated as a Result of this Project
Reduced Maintenance Costs: The successful implementation of the CONDUCTOR project development is expected to reduce these maintenance, repair and inspection costs significantly, through increase of repair reliability and reduction of time required for the performance of repairs. Contribution to Community Social Objectives The technology to be developed based on CSH heating is critical and will be a potential source of knowledge and development for the laboratories involved in the research program. In the field of bonding for repair advanced composite parts, the suppliers are presently American and European (GMI Aero, the SME leading of this project). a. Employment prospects and level of skills in the EU This project will restore confidence in the use of advanced aerospace materials by developing a more confident, efficient and easier to operate composite repair heating system, to be used during Standard maintenance operations. This will result in safeguarding and increasing the employment prospects in the European aerospace industry. b. Life extension of aircraft: This project will deliver new technology for improving safety and operational capability of aircraft, leading to an increase in operational life. The countries of former Eastern Europe, which have recently entered the EU, have aged aircraft fleets, which include 30-35 year old aircraft. In the absence of efficient heating solutions for their composite parts, these ageing aircraft may need to be decommissioned in the near future, to meet EU safety standards. c. Level of skill in EU: This project will lead to an improvement in the level of skills for European citizens, as it will implement new heating for repair bonding technology with more automated application. The project will develop and sustain EU expertise in these new technologies, particularly in versatile application of heating for repair of thick components or parts with complex geometries. d. Environmental impact Through enabling localized heating and the much higher rate of performance of the CSH heating method, compared to the conventional conduction heating, greening of aircraft maintenance is achieved, thus helping in reduction of the environmental impact of aviation. Contribution, to the expected impacts listed in the work programme. a. Trans-national cooperation: The widespread application of the project’s technology means that all countries will benefit. Adhesive bonding repair is a widely used technology throughout industry. During and after the project, participants will find other opportunities based on their pooled knowledge for mutually beneficial co-operation on products for other applications and market sectors. b. The project contributes to EU policy:
The EU’s horizontal policy of promoting innovation and the participation of SMEs is strongly supported as a result of collaboration between SMEs and RTDs across Europe. The aerospace industry is of vital importance for the growth and stability of the European economy since millions of workers are directly or indirectly dependent on it. European social and economic cohesion will benefit through the technology developed as a step forward in the safety of air-travel. The CONDUCTOR project will enable the aerospace industry to further expand existing standards to address structural composite repairs.
List of Websites:
Mr Roland Chemama, GMI Aero President, +33 6 77771473, roland.chemama@gmi-aero.com www.gmi-aero.com
Appropriate curing of the patch resin and the adhesive layer is an essential step to secure the integrity and the sound mechanical performance of a bonded composite repair. Today, the required elevation of temperature is usually achieved by means of a resistance heating blanket, which conduct heat to the repair area, regulated through closed loop temperature control, using spot temperature measurements. Heating Blankets for Composite Repair are presently designed by GMI Aero to fullfil a large range of cases in terms of geometry, shapes and temperature levels. The techniques of fabrication is based on encapsulating NiCr wires between two silicone sheets to ensure electrical isolation.on routing NiCr wires on silicone sheet. The encapsulation between two silicone layers assure electrical isolation. Even if this method is rather «simple» and allows to offer products that present excellent performances, technicians of MROs and Airlines are always frustrated not to have the possibility to manufacture in the field a product that can be tailored to the dimensions of the patch. The answer to such request is the Conductor Technology, which has been jointly developed by GMI and NTUA, within the frame of Cleansky. With this innovation, the quality of bonding operations will be improved and productivity will be increased by totally suppressing the lead time for heating element fabrication. The product will appear for the user as a standard silicone blanket that integrates a mesh of specially coated fibers. These fibers conduct electrical power in a distributed way over the whole surface of the blanket thus gaining in homogeneity. Furthermore, the special weaving of the fibers allows for cutting the blanket in different shapes whenever there is the need to follow contours that inhibit the use of a standard rectangular heating blanket. Power wires installed at pre-defined spots allow easy connection for power supply.The connectors for the power delivery wires have been specially selected to be easily mounted with maximum safety. Main Benefits for the end-user: a) This innovation delivers to the final user the benefits of having a “customised for the application” heating blanket manufactured in place, rather than having to order a special circuit, resulting in the total suppression of lead time for the procurement of heating blankets, b) High versatility in the design of geometrical patterns ; the user is able to adapt the shape of the blanket to a special geometry in order to distribute heat where it is strictly necessary, thus improving the heat management process. Conductor is the answer, in the context of repairing new advanced composite structures, to the search for tailored-made heating blankets adapted to the Thermal signature of the part, c) The fitting to the geometry of the repair area leads to the minimization of risk to overheat areas outside the repair zone, d) Prepared blankets could be further cut in smaller shapes if required, e) High homogeneity in temperature. The heating circuit develops heat with high quality of homogeneity in terms of temperature distribution, f) Conductor is compatible with the existing GMI Aero family of bonding consoles for temperature and power control, g) The Conductor technology allows also to apply for Multi Zone Heating solution (several blankets to cover a large area) and thus can be implemented with existing GMI-Anita Bonding with 2, 4, 6 zones,...
Project Context and Objectives:
The main concept driving the CONDUCTOR project is to apply the CSH principle for the development of special heating equipment and associated methodology that will constitute the basis of a next generation bonding repair equipment, to perform high quality, efficient and cost effective repair curing. This will lead to an environmentally friendly, low-energy, low-cost and easily interfaced solution for a future operational field bonding equipment, that will achieve better repair quality through minimization of temperature inhomogeneity problems.
Consequently the main objectives of this proposal, through the application of the CSH principle for the development of special heating equipment and associated methodology would be:
a. Achievement of more homogeneous temperature distribution within repair areas, leading to improvement of composite repairs quality.
b. Increase of overall repair process robustness, through minimization of elements (cables etc.) exiting vacuum bagging and easier adaptation to 3D geometries.
c. Reduction of overall power requirements, as the area to be heated and the overall thermal losses will be significantly lower compared to conventional heating methods.
d. Increase of repair speed, through:
i) Shortening of time to prepare vacuum bag, given the reduction of cabling.
ii) Possibility to perform steeper temperature increase, if required, given the energy excess provided by the CSH method.
e. Reduction of overall repair costs, due to the factors mentioned above.
Increase of range of applicability of bonded composite repairs, by ensuring the reliable achievement of specified temperature homogeneity requirements for more complex repair cases, as well as for composite to metal repairs
For the achievement of the above mentioned objectives, there were 4 technical Work packages in order to perform the research, development and testing activities of this project:
WP1 contains the definition of the main design parameters and repair process constraints that need to be taken into consideration for the preparation of the specifications and the overall design of the new CSH system, leading to a Preliminary Design Review (PDR). As a result, the overall design specifications of the new equipment will be concluded in this WP. A detailed thermal mapping using numerical simulation will be performed, in order to couple CSH to the developed temperature field and specify the foil configuration requirements. Finally, the first prototype of the PS&CU will be developed and the appropriate CSH foils will be selected.
Within WP2, the CSH device optimisation activities will be performed in order to achieve the set specifications. Moreover, within this WP the appropriate software will be developed, in order to tailor the system performance to the actual application requirements. The outcome of this Task will be an optimized prototype, the specifications of which will be frozen during the Critical Design Review (CDR) to be performed during the final steps of this WP.
In WP3, the first part of the testing of the developed CSH curing tool will take place, in cooperation with the Topic Manager. A reliability and robustness study will be prepared and will be verified against practical results, in order to evaluate the overall performance and robustness of the method. The outcome of this WP, will assist in the preparation of an upgraded CSH heating device to be further tested on curved CFRP structures.
In WP4, the second part of the testing of the developed CSH curing tool will take place on curved CFRP structures, in cooperation with the Topic Manager. A reliability and robustness study will be prepared and will be verified against practical results, in order to evaluate the overall performance and robustness of the method. Moreover, within this WP the overall CSH methodology will be structured, to permit direct application of the developed equipment by the ECO ITD.
Project Results:
Within WP1, the definition of the main design parameters and repair process constraints that need to be taken into consideration for the preparation of the specifications and the overall design of the new CSH (Conductive Skin Heating) system have been specified, as listed in this Deliverable. It is well understood that, given the R&D nature of the project, potential changes to these requirements may be performed during the evolution of this project, as required, after discussion and agreement among involved entities. Moreover, an extensive comparative evaluation study has been performed in order to select the CSH foils material to be used will this project, complying to the requirements set out in Deliverable 1.1. For this reason, several types of carbon veil (foils) have been identified by the Consortium as candidate CSH element, together with metallic foils and expanded metallic foils. It has been decided that two (2) materials comply with most of the project requirements, exhibiting corresponding advantages/disadvantages (Nickel Coated Carbon veil & expanded stainless steel foil). As, it was not evident which of these two materials will be most appropriate for fulfilling the CONDUCTOR objectives, it has been decided to proceed with both materials to the following steps of this project. Within WP2, the optimized prototype of the CSH hardware has started being prepared, including all elements (power supply, flexible foils, connecting parts, conductors etc.) following extensive laboratory tests which was performed on the first prototype equipment. The main application of this prototype equipment will be to optimize the CSH parameters and fine tune accordingly the heating control algorithm, as described in the following Task. The outcome of this Task was an optimized prototype of all equipment developed, the specifications of which was frozen during the Critical Design Review (CDR). Within WP3 the first part of the testing of the developed CSH curing tool took place, in cooperation with the Topic Manager. A reliability and robustness study was prepared and verified against practical results, in order to evaluate the overall performance and robustness of the materials developed and of the methodology used. This Task involved extensive field testing of the developed CSH curing tool equipment and associated equipment and methodology (vacuum bagging specificities, installation requirements, temperature measurement strategy and thermocouple placement guidelines, connectors etc.) for CSH of flat bonded composite repairs. In order to guarantee that all practical application parameters have been taken into consideration, this work was carried out on panels that the Topic Manager has provided and was also demonstrated at the Topic Manager’s facilities. Within WP4 the second part of the testing of the developed CSH curing tool took place. The main goal of this task was to verify the capability of the CSH blanket to operate on curved surfaces. By taking into account all the lesson learned in WP 3, the equipment was improved in areas such as the control software and the blanket production techniques. On the second step, a complicated aircraft part with medium radiuses was selected as a representative structure to test the limits of the new blankets application and also demonstrate its abilities. As a conclusion, the work performed within the project has generally been in line with the provisions of the Dow, while additional elements and effort has been added, as analyzed previously. The CONDUCTOR project has been delayed by approximately nine (9) months and therefore, a request for the extension of the CONDUCTOR project has been submitted and was approved by CSJU, with a new finishing date of 31/8/2014. No other contractual and / or financial provisions were affected, whatsoever.
Potential Impact:
Replying directly to JTI CfP, the primary drivers for CONDUCTOR relate to safety, economic and societal issues. The application of the proposed advantages to the composite repair process will improve reliability during operation, improve performance and minimise the time the aircraft needs to spend on the ground for repair, which are among the main targets of the CleanSky JTI. This will permit increased aircraft availability and lower maintenance costs to be incurred by the operating companies. Savings Generated as a Result of this Project
Reduced Maintenance Costs: The successful implementation of the CONDUCTOR project development is expected to reduce these maintenance, repair and inspection costs significantly, through increase of repair reliability and reduction of time required for the performance of repairs. Contribution to Community Social Objectives The technology to be developed based on CSH heating is critical and will be a potential source of knowledge and development for the laboratories involved in the research program. In the field of bonding for repair advanced composite parts, the suppliers are presently American and European (GMI Aero, the SME leading of this project). a. Employment prospects and level of skills in the EU This project will restore confidence in the use of advanced aerospace materials by developing a more confident, efficient and easier to operate composite repair heating system, to be used during Standard maintenance operations. This will result in safeguarding and increasing the employment prospects in the European aerospace industry. b. Life extension of aircraft: This project will deliver new technology for improving safety and operational capability of aircraft, leading to an increase in operational life. The countries of former Eastern Europe, which have recently entered the EU, have aged aircraft fleets, which include 30-35 year old aircraft. In the absence of efficient heating solutions for their composite parts, these ageing aircraft may need to be decommissioned in the near future, to meet EU safety standards. c. Level of skill in EU: This project will lead to an improvement in the level of skills for European citizens, as it will implement new heating for repair bonding technology with more automated application. The project will develop and sustain EU expertise in these new technologies, particularly in versatile application of heating for repair of thick components or parts with complex geometries. d. Environmental impact Through enabling localized heating and the much higher rate of performance of the CSH heating method, compared to the conventional conduction heating, greening of aircraft maintenance is achieved, thus helping in reduction of the environmental impact of aviation. Contribution, to the expected impacts listed in the work programme. a. Trans-national cooperation: The widespread application of the project’s technology means that all countries will benefit. Adhesive bonding repair is a widely used technology throughout industry. During and after the project, participants will find other opportunities based on their pooled knowledge for mutually beneficial co-operation on products for other applications and market sectors. b. The project contributes to EU policy:
The EU’s horizontal policy of promoting innovation and the participation of SMEs is strongly supported as a result of collaboration between SMEs and RTDs across Europe. The aerospace industry is of vital importance for the growth and stability of the European economy since millions of workers are directly or indirectly dependent on it. European social and economic cohesion will benefit through the technology developed as a step forward in the safety of air-travel. The CONDUCTOR project will enable the aerospace industry to further expand existing standards to address structural composite repairs.
List of Websites:
Mr Roland Chemama, GMI Aero President, +33 6 77771473, roland.chemama@gmi-aero.com www.gmi-aero.com
