1 Bonded Repair of Primary Composite Structures

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1 Bonded Repair of Primary Composite Structures

Innovation Track 1
The project focuses on the bolt free repair of aerospace primary structures using composite patches adhesive bonded to the damaged area. The goal is to investigate and define materials and repair processes capable of restoring the operational capability of the damaged structure in compliance with the airworthiness certification requirements. Research will be done into methods for certification of the adhesive bonded repair including the use of Structural Health Monitoring (SHM) systems. A representative demonstrator will be designed, manufactured and tested.

Parties involved:  NLR and Fokker Services

Timeline: 1st of March 2017-2019

Project execution

The project contains a number of milestones as indicated below:

Milestone 1:
Literature review (done, May 2017)

Purpose of this MS is to get a good view on the present state of the art on composite repair procedures and certification issues.

Milestone 2: Determining the demonstration structure (done, November 2017)

As there are many composite materials and repair methods in use a selection of a representative demonstration platform is needed. The repair of a sandwich structure was selected to demonstrate the repair and airworthiness certification of the repair.

Milestone 3: Determining the materials and material properties (done, April 2018)

The material properties are needed to analyse and design the repair. The properties were partly obtained by literature review and partly by performing mechanical tests.

Milestone 4: Determining the certification approach (done, May 2018)

As there are no standard certification methods available for adhesive bonded repairs on aerospace structures alternative certification methods have to be investigated. Finally an approach was found were the initial bond strength was substantiated by testing of traveler patches surrounding the repair patch together with an in-service monitoring of the repair patch behaviour by a dedicated SHM system.

Milestone 5: 
Design and analysis of the repair (done, August 2018)

Methods have been developed for a quick assessment of the remaining strength of a damaged structure and the restored strength in case of a bonded patch repair. Within this milestone the demonstrator repair was designed and analyzed.

Milestone 6: Manufacturing of the demonstration repair (done, November 2018)

The repair was manufactured and the repair demonstrator is ready for testing.

Milestone 7: Demonstrator test (in progress, April 2019)

Execution of the static and fatigue test program.