The research project dealt with the development of Advanced CFRP Technologies for the cost-efficient, green and reliable manufacturing of stiffened wing large Aerostructures by Liquid Resin Infusion (LRI). The LRI process, especially for large scale structures, is not yet well mastered and validated simulation tools are a necessary requirement to properly industrialise this technology.
Two major points were addressed in this project: the development of an optimised simulation methodology for LRI process with large parts and stiffened wing skin panels, and the generation of an in-depth understanding of the flow phenomena in LRI and more experimental data and experience.
The whole methodology was based on commercial software but considering an accurate and cost-efficient physical approach.
Second innovation lies in the design and development of an innovative test bench for validation and development of the LRI technology. This test bench integrated the latest generation dielectric sensors allowing us to get accurate results.
In the Clean Sky JTI, new technologies for green manufacturing have been studied in the frame of both GRA (Green Regional Aircraft) and ED (Eco-Design) ITDs with the objective of producing low weight/eco-friendly aircraft components with competitive manufacturing costs. In order to achieve this purpose ALENIA AERMACCHI, Leader of the GRA ITD and Member of the ED ITD, has conducted several studies and launched various initiatives aimed at the development, optimization and industrialization of Liquid Resin Infusion (LRI) processes. Specifically, ALENIA AERMACCHI steered the Liquid Resin Infusion (LRI) process executed “Out-of-Autoclave” (without pressure) for the one shot manufacturing of wing box stiffened panels in composite material, with the aim of reducing impact on weight, on the environment and on life cycle costs, enabling synergies between GRA and ED ITDs, through the support of Clean Sky Members and Partners, selected by the Call for Proposals.
LRI processing is one of the most promising technologies for application in the aeronautic sector as it should provide good properties within an acceptable cost range also reducing the manufacturing risk of large complex structures. It consists in infusing the liquid resin in a pre-shaped dry fabric preform. The preforms (e.g. skin and stringers) are supported by specially shaped moulds and fairing bars and positioned with special templates. The resin is heated and injected into a vacuum bag using special means. The cure cycle results then in a fibre reinforced structure. The LRI is an alternative to other similar processes like the Resin Film Infusion (RFI) in which the resin is pre shaped in film sheets, interlayed between the fabric layers or placed between the mould and the preform; the Controlled Atmospheric Pressure Resin Infusion (CAPRI); the Resin Transfer Moulding (RTM) and others. All the Infusion techniques compete with the well-known and largely used autoclave curing of pre-preg composites.
The PLIT project, launched in the GRA “Low Weight Configuration” domain (Topic Manager SICAMB), arises under these initiatives contributing to provide a scientific approach to the physics of the LRI process by the creation and validation of a numerical simulation model to study the resin flow during the impregnation stage. This model shall be used to identify possible causes for non-uniform distributions of resin flow that may cause dry spots, poor saturation of the pre-form, partially filled composite parts, defects, etc.
The activities of the PLIT project were developed by a consortium led by the CIDAUT Foundation (Spain), together with ITRB (Cyprus) and PBLH International Consulting (Belgium) in close communication with the Topic Manager (TM) SICAMB. The main innovation achieved in this project was the development of an optimized numerical approach for an accurate and efficient simulation of LRI processes for big parts such as stiffened wing panels. Another important achievement of the project was the development of an innovative test bench, that was designed starting from Members indications, and built for the manufacturing of stiffened wing panels at the TM site to validate the simulation results. Laboratory characterizations of key material parameters such as permeability and viscosity for the selected materials were key factors for achieving a good correlation between experimental and simulation results.