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Development of advanced microwave and light-weight high-speed thermo-response mould technology for woven textile-reinforced thermoplastic components

Deliverables

The moulds developed in the project were enhanced test moulds for test specimen as well as prototype moulds for the HTex and JETex process. The second mould is a mould for a pressure vessel produced with HTex process. Mould 2b is an auxiliary mould for the injection moulding of silicone bubbles which was used to generate the necessary inner pressure for the HTex process.
The prototype of the dynamic heating and cooling system consists of a basic two-circuit device. This allows having fast and cost-efficient work during the experimental and optimisation phase of the process development and prototyping. The basic concept was developed by Regloplas in co-operation with StructoForm. The concept was further developed and optimised on several technical meetings in-house Regloplas and at StructoForm lab. Definition of the dynamic heating and control system: Prototype: two circuit heating and cooling apparatus Processes: feasible for JETex and HTex processes Textiles: adaptable to various pre-forms and textiles First step: basic set-up with modular plate cavity and thermoplastic resin injection Second step: high temperature test up to 300° C and test with JETex process Third step: step-wise test and adaptation of on-line monitor and process control Forth step: processing with various materials, prototype production and monitoring. The two-circuit system is based on enhanced state-of-the-art oil heating systems of REGLOPLAS. This was further developed and two units combined and integrated into one construction. The process control allows to cool one circuit and heat the other circuit independently (e.g. low circuit: 70° C, hot circuit: 160° C). Then, firstly the hot circuit heats up the cavity. When the part is consolidated in the mould, the cold circuit is opened and pushes the hot oil out of the cavity back into the hot circuit. Then the cold oil circulates through the cavity and cools it down rapidly. The adaptation of the preliminary prototype was completed. The detailed concept for more complex heating and cooling elements are finished. Two test systems of the high temperature dynamic system are available for further process development. New high temperature valves have been developed and successfully tested up to 10.000 cycles. They are integrated in the advanced second version of the heating unit. The heating and energy balance tests result up to now in a cycle time reduction by 50 % in comparison to conventional heating systems.
The moulds developed in the project were enhanced test moulds for test specimen as well as prototype moulds for the HTex and JETex process. This mould is a variant of the second mould for the pressure vessel (HTex process), consolidated by microwave heating. The main parts of this mould are manufactured from a microwave-transparent material. Based on feasibility studies PEEK was selected as appropriate mould material. A PEEK mould as final step for the concept was completed.
Investigations on HF and µ-wave heating of the resin are made to develop an electromagnetic heating system for liquid moulding. The development of electromagnetic energy heating is highly depended on the thermoplastic resin system used. The electromagnetic energy has to be optimised to guarantee a response of the chemical structure of the molecules. The domestic use of microwaves to heat up food is the most commonly known application of electromagnetic energy. In industry microwaves are used to de-ice bulk materials and mostly also food. The advantage of using microwaves over traditional heating technologies is that if the right energy response spectrum can be found processing times can be dramatically shortened. But also other electromagnetic energy sources are of interest. Basic investigations have been completed.
The moulds developed in the project were enhanced test moulds for test specimen as well as prototype moulds for the HTex and JETex process. The first mould is a mould for test plates for the HTex and JETex process. - Basic tool frame for manufacturing of different plate thickness. - Mould concept with ¿diving¿ split line.
Textile structures were developed that enable cost-efficient and automated production of performs that are tailored for a good compromise between process ability in the subsequent impregnation/consolidation step and mechanical performance of the finished product. The result was different for the two processes of interest. JETex process: - Two versions of braiding to produce beam-like structures (e.g. the leaf spring prototype), overbraiding of a sheath of uniaxial cable yarns and overbraiding of a mandrel with several layers. - Innovative means to tailor/enhance the permeability of the performs (= efficient impregnation in the JETex process). - Experimentally determined mechanical properties of composites based on the braided performs. - A set of performs for the JETex prototype (leaf spring) HTex process - Knowledge about how different textile structures based on hybrid yarns behave in the HTex process - Experimentally determined thermal and mechanical properties of composites based on several types (eight) of hybrid yarn. - Bio-polymer formulation for injection moulding requirements and experience with sandwich injection moulding technology. - Technology for filament winding and braiding on thermoplastic in-liners to produce performs feasible for consolidation by the HTex process (multifunctional in-liner: mandrel during performing, bladder during consolidation, sealing liner during service) - A set of performs for the HTex prototype (pressure vessel).
The JETex prototype which was chosen and designed is a leaf spring for transportation applications. Result: - Preliminary set of design allowable established; - Parameterised FE-model for computer simulations created; - Geometry that optimise trade-off between cost effective manufacturing and performance; - Optimised textile perform; - Manufactured and tested prototypes.
The moulds developed in the project were enhanced test moulds for test specimen as well as prototype moulds for the HTex and JETex process. The second mould is a mould for a pressure vessel produced with HTex process The main part of the second mould is an aluminium mould for HTex process, based on a massive metal block with high thermal conductivity. An aluminium mould as first step for the concept was completed.
Basic development and optimisation of processing and feasibility tests for the HTex process is required during the project. Therefore, the processing tests using fibre structures, inserts and pre-forms were performed. The trials were partially done simultaneously to the stepwise adaptation and modification of the lab equipment like heating, performs and the moulds. The HTex process variants are first individually tested and optimised. They are establishing one development line of the required processing basis and for the development and optimisation of the HTex technology and their applications. The processing tests with HTex started with various thermoplastic hybrid textiles. The process development was done with new constructed enhanced test moulds. The trials e.g. with the flat textile reinforced test plate gave knowledge about the behaviour of the thermoplastic hybrid textiles. In a second phase trials were carried out with the prototype mould for the pressure vessel. The silicone bladder is used during HTex processing inside mould 2(a) to generate the necessary inner pressure on the textile pre-form. After consolidation of the vessel prototype, the bubble can be pulled out from the mould as ¿collapsing¿ core. It showed that the bonding of the thermoplastic material to the textile perform was very dependent on mould heating conditions and the relevant process parameters: - Mould-temperature. - Order of mould heating and cooling phase. - Holding / consolidation time. - Pressure during consolidation. - The type of the matrix material has a strong influence on the bonding between matrix and textiles. - A variant with an over-braided core was successfully developed and tested for the HTex process. The final test of the HTex process was done with the PEEK mould (2c) and heated with the microwave heating system
The moulds developed in the project were enhanced test moulds for test specimen as well as prototype moulds for the HTex and JETex process. The third mould is a prototype mould for the JETex process. It was manufactured from aluminium with optimised temperature system.
Basic development and optimisation of processing and feasibility tests for the JETex process is required during the project. Therefore, the processing tests using fibre structures, inserts and pre-forms were performed. The trials were partially done simultaneously to the stepwise adaptation and modification of the lab equipment like heating, injection unit and the moulds. The JETex process was first individually tested and optimised. The required processing basis is established for the development and optimisation of the JETex technology and its application. The processing tests with JETex started with two thermoplastic resins, pre-polymers as basis for polyamide (PA) and polybuthyleneterephtalat (CBT). The process development was done with new constructed enhanced test moulds. Finally the CBT system was chosen and used for development and test. The trials e.g. with the flat textile reinforced test plate gave knowledge about the behaviour of the thermoplastic impregnation. It showed that the bonding of the injected thermoplastic material to the insert-matrix material was very dependent on mould filling and the relevant process parameters: - Resin temperature. - Mould-temperature. - Order of mould heating and cooling phase. - Mould filling phase / injection of resin. - Holding / consolidation time. - Geometry and position of gating system. - The type of the matrix material as well as the surface treatment of fibres has a strong influence on the bonding between matrix and textiles.
The process control consists firstly of the monitoring of dynamic heating and cooling processes. Monitoring tests with the modular plate mould in the heating up and cooling phase were carried out successfully on the 200 ton lab system with several thermoplastic resins. Before start of injection, the fast heating phase is started. This resulted in heating up times from 70° C up to 160 ° C in app. 120 seconds. Simultaneously with start of the cooling phase of the 200 ton lab system, the fast cooling phase of the unit started. The cycle is completed after app.180 seconds at 70° C. The monitoring tests show the high applicability of the dynamic device for the process optimisation with JETex and HTex mould technology. The on-line temperature monitor is part of the enhanced process control of the project. The main applications are: - On-line monitoring of mould temperature; - Determination of cycle time; - Temperature of hot circuit; - Temperature of cold circuit; - Flow rate; - Energy balance measurements; - Possibility of heat exchange between the cold and hot circuit (recovery of energy). The on-line monitor is a temperature monitoring unit to be used for consolidation analysis of the materials used with the JETex process. The modular plate mould was used during the injection phase. The tests were successfully completed on the 200 ton lab system with several thermoplastic resins. The monitor prototype consists of two computer systems which are working in parallel during the processing cycle. One system is capable of writing processing data shot by shot on a hard disk. Machine data like the injection piston movements during the mould filling phase, the hydraulic pressure, injection speed and the mould temperature can be processed and used for analysis. The data are shown on-line on a screen as shown in the following pictures. The second computer gets ultrasound data directly from the mould and pressure and temperature signals from the first computer. This data can be used to analyse the processing phase quite sensitive, because the ultrasound signal changes its amplitude during the consolidating phase of the resin. If gas is injected into the resin to form a hollow bubble in the centre of the part, the ultrasound gives a clear signal change when the gas passes the ultrasound sensor. So, all signal changes indicate significant steps of the injection and consolidating phase and can therefore be used for quality analysis and quality assurance measures. The Monitoring system was successfully set-up and functionally tested. Start of systematic processing studies is planned during the second project year in combination with the processing control of dynamic heating.
The HTex prototype which was chosen and designed is a pressure vessel for transportation applications with one-side or two-sided openings. Result: - Generation of 3D-CAD model and spatial geometry of pressure vessel; - Preliminary set of design allowable established; - FE-model for computer simulations created; - Several evaluated alternatives for connection design (thread, flange, metal insert); - Fibre lay-up alternatives that optimise trade-off between cost effective manufacturing and performance for different textile methods; - Multifunctional in-liner concept (performing mandrel, consolidation bladder, sealing liner); - Manufactured and tested first prototypes.
The filling process of moulds is simulated, which are carrying fibre and textile reinforcements for the produced components. Methods to model non-Newtonian fluid flow through fibre beds. A two-phase continuum constitutive model has been developed and FE-implemented for simulation of the HTex process, which involves simultaneous impregnation and forming A new method to determine thermal contact conductance between metal tooling and composite has been developed. Using the method a set of thermal contact conductance data has been generated. The thermal contact conductance is of importance both for JETex and HTex process simulations. A thermo-chemo-mechanical process model has been developed for the JETex process and implemented in the FE-program ANSYS. The model includes both thermal and mechanical part-tool interaction.

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