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Development of an innovative welding process for the rapid assembly of thermoplastic brackets to thermoset-matrix composite structures

Periodic Reporting for period 1 - BRACKETWELD (Development of an innovative welding process for the rapid assembly of thermoplastic brackets to thermoset-matrix composite structures)

Reporting period: 2016-01-01 to 2017-06-30

The BRACKETWELD project deals with the development of a rapid assembly technology for the integration of brackets into structural elements like stringers and frames of modern aircrafts. Brackets are small elements used as local links between aircraft structure, systems and cabin. The state-of-the-art techniques for joining brackets or other small functional elements to the usual composite structural components are based on mechanical fastening and adhesive bonding. These joining processes are time consuming, and add significant labour and tooling costs to the assembly process, even for the attachment of such small components. Moreover, the adhesion strength achieved is often limited requiring dedicated surface treatments to be applied. An additional handicap for a strong adhesive bonding happens when the composite component is painted.
The general objective of the BRACKETWELD project is to contribute to the green and cost-efficient integration of system and aircraft structure by the development of an innovative technology for the rapid assembly of thermoplastic brackets in general, and in particular PEI brackets, to thermosetting composite components currently used in aircraft structures. This innovative assembly technology is based on the idea of using the fast and efficient ultrasonic welding technology to assemble thermoplastic brackets to thermosetting composite structural components.
The success in the development of the activities of the BRACKETWELD project will contribute to the development of the rapid assembly process for the integration of brackets and fittings into structural thermosetting composite components leading to significant advantages related to the reduction in weight (associated to the change form metal to thermoplastic brackets), assembly costs and energy reductions. The new capabilities for thermosetting composite components will have a positive impact for the reduction of current assembly times and costs, increasing the number of applications of composite lightweight materials in Transport Sectors for reducing vehicle weights, fuel consumptions and emissions.
Management and dissemination activities
WP2 has been dedicated to the definition and optimization of an efficient Test Method for the evaluation of materials compatibility. The definition of quick test method was based on the analysis of the inputs provided by the Topic Manager regarding materials (brackets and epoxy prepregs), welding parameters (frequency, pressure, amplitude) and specifications for the assembly performances. This test method starts from a methodology to determine the welding parameters, followed by the evaluation of the welding strength and the bond strength at the joint, and is completed with additional laboratory analysis that complete the knowledge of the materials compatibility.
WP3 has dealt with the research of the most suitable surface media for welding PEI brackets. Research activities included the selection/development of a suitable material formulation and the optimization of surface media parameters like thickness and morphology (porosity). A final surface media has been selected attending to the welding and bonding strength shown with the previously developed test method.
In the next period, WP4 will validate the developed joints in a demonstrator.
The general concept of using a thermoplastic surface media compatible with the thermoplastic brackets (attending ultrasonic welding requirements) and at the same time being able to reach a very high level of adhesion with the thermosetting resins used for the manufacturing of composite structural components is still in the first levels of development, basically TRL-2 while the BRACKETWELD project aims to contribute to the achievement of TRL-3 and TRL-4, by the definition of innovative concepts for the development of the suitable surface medias and the creation of an efficient methodology for the assessment of assembly performances in laboratory conditions. The success in the development of the project activities will allow the LPA program to continue with future developments and achievement of higher TRL levels (objective for Clean Sky 2 activities), through the manufacturing of demonstrators for the validation of integrative concepts for structure, system and cabin.