FRAMES projects partners have been focusing on the development of simulation model for thermoplastic composites fiber placement, stiffeners manufacturing process simulation and trials, as well as engineering tooling solution for manufacturing skin-stiffener assembly demonstrator.
FRAMES advances simulation of xenon heating device, which deliver highly energetic short duration pulses collected and delivered by a quartz light guide to the thermoplastic material during fibre placement lay up. Goal was to deliver a reliable simulation tool able to predict processing temperatures achieved as a function of entry pulses parameters and heating device configuration. Work started by the measurement of output power, optical measurements to evaluate the energy level by wavelengths and system efficiency. Then the influence of the quartz light guide position relative to the material has been measured. Finally the optical and thermal behavior of the composite material has been characterized. Optical results were used to feed a simulation model, and physical fibre placement trials have been performed to validate the simulation approach. The model has been further tuned to take into account heat accumulation into the system during long lay up runs. The solution is now available to predict processing temperature according fibre placement system configuration, lay up speed and materials characteristics.
Process simulation has been also applied to thermoplastic composite stiffeners manufacturing : the aim was to simulate final part geometry after molding, including thickness and spring-in behavior, design the tooling geometry and features in accordance and manufacture prototypes of Clips, Omega stringers, Z-Frames and a J-Beam. The clips has been produced from flat blanks using the continuous compression molding (CCM) process followed by a hot stamping step. A full range of 10 clips references have been delivered. Production flow adopted for Omega stringers share a similar approach : a first production of CCM flat blanks, followed by a Continuous Hot Stamp Forming of plates to form the omega cross section. A single profile has be used to produce two Omega stringers reference. Then an additional forming step has been defined and applied to one stringer end to get the final geometry. Considering the highly curved Z-Frames, five different production schemes have been assessed, and the one selected relies on two steps : manufacturing of flat blanks by automated fibre placement (AFP), then hot stamping of blanks to get the final Z geometries. Three hot stamping tools have been designed and manufactured, and flat blanks were hot stamped including trials to investigate the best solution to place and retain correctly the preform in the right position to the stamp tool, and to minimize impact on preform quality.
For the J-Beam, the work has been divided into four different components to form the final J-profile : Plate, Gusset, U profile and Z-profile. A similar process to the Z frames is used. The main difference is on the tooling which features movable parts resulting in a multistep forming. Forming trials have been done at small scale to evaluate the technical solution to be transferred to full scale. Flat blanks have been laid up by AFP and then hot stamped into U and Z-profiles. J-Beam plate has been manufactured from a CCM plate with a ply drop, from which multiple J-Beam plates could be cut out. The gussets were manufactured by milling straight 2D profiles.
Together with the stiffeners, a skin-stiffener co-consolidation tooling solution has been investigated. A combination of INVAR grades with integrated thermal regulations channels have been selected to reach consolidation temperature with optimized ramp up. Calculations of thermal expansion of each tooling elements has been done to ensure proper consolidation forces applied to skin and stiffeners during thermal cycle. Two toolings set have been delivered : A small scale tooling featuring a geometry directly taken from the full scale demonstrator in the most critical area, with the self-heated capacity able to co-consolidate a skin-stiffener part, and a full scale tool limited to skin side and J-Beam, featuring the heating and cooling channels able to implement a self heating system, bringing the capacity to lay up the skin by fibre placement and consolidate a J-Beam to skin assembly.
FRAMES outcomes are now going to be applied into the manufacture of full scale thermoplastic rear end demonstrator made by the DLR.
Project activities and achieved results have been publicly disclosed through Linkedin posts. A project movie focusing on key aspects support the outcomes spread. Scientific publications have been released by Heraeus focusing on simulation work around the heating system.
Key exploitable results will embrace both further research activities partner' relevant commercial use : Optical thermal model is going to support customer system optimization to thermoplastic lay up and will serve further systems development. High rate manufacturing process for TP stiffeners will be exploit to widen the scope of applicable aerospace components and reinjected into new development projects. Co-consolidation tooling solution is intended to be scaled up to reach new applications in terms of complexity and temperature range to reach higher complex thermoplastic panels.
