Implementation and Validation of numerical damage tolerance prediction method for bonded CFRP joints and large bonded repairs
Topic(s) : Special Sessions
Co-authors :
Thomas KRUSE-STRACK (GERMANY), Nantje STEINBERG (GERMANY), Roman STARIKOV , Lars ABERSPACH , Alexander ZASTROW (GERMANY)Abstract :
One key technology for the development and implementation of composite repairs is a suitable joining technology. Conducting a weight, performance and cost tradeoff, bonding offers the best opportunities as joining technologies for composites. Therefore the logical consequence is the stringent development and implementation of bonded repairs for commercial transport aircrafts as A350.
Today the application of bonding technology for primary aerospace structures is limited due to the certification guidelines and standard means of compliance as defined in the certification documents FAA AC-20-107B and EASA AMC20-29. State of the art for the application and certification of bonding in major loadpath structures is the widely used chicken rivet which is limiting the benefits of the application of composite bonded joints due to thickness and layup requirements for the bolt. In addition for repairs the state of the art Bonded Repair Size Limit (BRSL) applies and requires limit load capability in case of a bondline failure.
The presentation outlines a way to achieve a certified bonded repair beyond today's bonded repair size limits based on the consequent application of the Damage Tolerance principles addressed by AC-20-107B and AMC20-29 and the related novel justification approach for large bonded repair and bonded primary structures without chicken rivets.
The current research conducted within Airbus in the frame of LuFo VI-1 JoinDT will be presented, focussing on the development of a damage tolerant sizing and simulation method and fatigue testing on element and structure detail level for the validation of the numerical methods for damage tolerance and fatigue crack growth behavior. The transfer of the developed scientific high fidelity simulation tool chain, covering damage initiation (impact simulation), inter- and intralaminar crack growth and residual strength, into an industrial application environment will be outlined and the influence on new certification boundaries for lange bonded repairs will be presented as well as the results from the performed fatigue test campaign on element level on wide single lap shear specimens (WSLS).
The results will be presented in the context of the targeted Airbus Application scenario for large bonded composite repairs. As concussion the results will be discussed versus the current certification boundary conditions and a roadmap towards a certified large bonded repairs overcoming todays bonded repair size limits and enabling also future utilization of bonding for major load path structures for the next generation of composite airframes will be presented.
Today the application of bonding technology for primary aerospace structures is limited due to the certification guidelines and standard means of compliance as defined in the certification documents FAA AC-20-107B and EASA AMC20-29. State of the art for the application and certification of bonding in major loadpath structures is the widely used chicken rivet which is limiting the benefits of the application of composite bonded joints due to thickness and layup requirements for the bolt. In addition for repairs the state of the art Bonded Repair Size Limit (BRSL) applies and requires limit load capability in case of a bondline failure.
The presentation outlines a way to achieve a certified bonded repair beyond today's bonded repair size limits based on the consequent application of the Damage Tolerance principles addressed by AC-20-107B and AMC20-29 and the related novel justification approach for large bonded repair and bonded primary structures without chicken rivets.
The current research conducted within Airbus in the frame of LuFo VI-1 JoinDT will be presented, focussing on the development of a damage tolerant sizing and simulation method and fatigue testing on element and structure detail level for the validation of the numerical methods for damage tolerance and fatigue crack growth behavior. The transfer of the developed scientific high fidelity simulation tool chain, covering damage initiation (impact simulation), inter- and intralaminar crack growth and residual strength, into an industrial application environment will be outlined and the influence on new certification boundaries for lange bonded repairs will be presented as well as the results from the performed fatigue test campaign on element level on wide single lap shear specimens (WSLS).
The results will be presented in the context of the targeted Airbus Application scenario for large bonded composite repairs. As concussion the results will be discussed versus the current certification boundary conditions and a roadmap towards a certified large bonded repairs overcoming todays bonded repair size limits and enabling also future utilization of bonding for major load path structures for the next generation of composite airframes will be presented.