Processing of Thermosets Composites

Transcription

1 Spring Semester L Manufacturing of Polymer Composites Processing of Thermosets Composites Paolo Ermanni 9 March 2017 Manufacturing of Polymer Composites - Processing of Thermosets Composites

2 Contents Introduction Wet-Lamination Process Flow in porous media Resin curing kinetics Resin viscosity Manufacturing of Polymer Composites - Processing of Thermosets Composites

3 Selection criteria for manufacturing process Economical aspects Investments Equipment Tooling Labour costs Material Costs Series volume Cycle time Safety and health aspects Selection Criteria Technical aspects Structural features Design and fabrication of highly integrated monolithic structures (reduction of single parts) Manufacturing of highly complex shapes Easy integration of doublers, inserts damping materials and functional elements such as actuators and sensors. Surface quality Laminate features Mechanical properties Fibre architecture Fibre volume content Quality and reproducibility Manufacturing of Polymer Composites - Processing of Thermosets Composites

4 Top-level Process-chain from constituent materials to final part Fabrication route Constituent materials Layup, Preform Impregnation Manufacturing process Forming Curing Final part & material properties Physical and chemical processes Capillary driven flow Pressure driven flow Chemical reaction Material properties Quality features Fibre distribution Void content and distribution Delamination Fibre/matrix interface Fibre volume content Flemming, M.; Ziegmann, G.; Roth S.: Faserverbundbauweisen, Halbzeuge und Bauweisen; Springer-Verlag, Berlin Heidelberg 1996 Manufacturing of Polymer Composites - Processing of Thermosets Composites

5 Overview Flow- Processes Draping Processes Injection- Processes SMC, GMT LFI, E-LFI Filament Winding, Pultrusion, Automated layup Press technologies Autoclave RTM, VARI SCRIMP... Off-line Impregnation Prepregs Fibre Rovings Off-line Impregnation Textile Process Intermediate material Textile Process Multi-axial material Preforming Preform Weben Flechten Stricken Vernähen Wirken Sticken 3D-Form Manufacturing of Polymer Composites - Processing of Thermosets Composites

6 Contents Introduction Wet-Lamination Process Flow in porous media Resin curing kinetics Resin viscosity Manufacturing of Polymer Composites - Processing of Thermosets Composites

7 Wet Lamination technique Preparation Forming Impregnation Curing Demolding Preparation of fibre layers and cutting to desired shape and size Preparation of the mold Resin mixing Forming takes place by laying/draping the layers in resp. on the mold Wetting of the fabric Vacuum-bagging Curing usually takes place at room temperature. Post-curing at higher temperature is possible after removal from the mold. Demolding Post-processing Typical fibre material: glass fabrics vlies and mats Resin systems: Unsaturated Polyester, Vinylester, Epoxy Manufacturing of Polymer Composites - Processing of Thermosets Composites

8 Wet Lamination technique Preparation Forming Impregnation Curing Demolding Preparation of fibre layers and cutting to desired shape and size Surfacing ply Release agent Preparation of the mold Resin mixing Forming takes place by laying/draping the layers in resp. on the mold Wetting of the fabric Vacuum-bagging Curing usually takes place at room temperature. Post-curing at higher temperature is possible after removal from the mold. Demolding Post-processing Glass fibre mats, vlies and/or fabrics Simple molds No special requirements with regard to temperature resistance Mold material: often wood or resin Mold Mold reinforcement Manufacturing of Polymer Composites - Processing of Thermosets Composites

9 Wet lamination technique Preparation Forming Impregnation Curing Demolding Preparation of fibre layers and cutting to desired shape and size Preparation of the mold Resin mixing Forming takes place by laying/draping the layers in resp. on the mold Wetting of the fabric Vacuum-bagging Curing usually takes place at room temperature. Post-curing at higher temperature is possible after removal from the mold. Demolding Post-processing Manufacturing of Polymer Composites - Processing of Thermosets Composites

10 Wet lamination technique Preparation Forming Impregnation Curing Demolding Preparation of fibre layers and cutting to desired shape and size Preparation of the mold Resin mixing Forming takes place by laying/draping the layers in resp. on the mold Wetting of the fabric Vacuum-bagging Curing usually takes place at room temperature. Post-curing at higher temperature is possible after removal from the mold. Demolding Post-processing Manufacturing of Polymer Composites - Processing of Thermosets Composites

11 Main process features Well-suited for parts with complex geometries Fabrication of small and very large parts Easy integration of local reinforcements (dopplers) and inserts Good surface quality (on the mold-side) Typical fibre volume content: approx. 40% Long cycle time Low investments Open process Health & safety is a concern! Mediocre laminate quality and reproducibility. Part quality strongly depends on the skills of the technicians Manufacturing of Polymer Composites - Processing of Thermosets Composites

12 Which of those parts would you fabricate in wetlamination technique? 1. Tooling / Mold 2. Airplane structural panel 3. Boot Hull 4. Space antenna 5. F1 Chassis Manufacturing of Polymer Composites - Processing of Thermosets Composites

13 How relevant are following criteria for the selection of the appropriate fabrication process? Criteria Geometrical complexity Tolerances + = + Surface quality = + Achievable fibre volume content Mechanical properties Laminate quality = -- + Reproducibility Investment costs Labor expenses Material costs Number of parts p.a. -- = Cycle time Criteria is not relevant -- - = + Criteria is very relevant Manufacturing of Polymer Composites - Processing of Thermosets Composites

14 Typical application fields Mold construction Ship hulls Wind energy Manufacturing of Polymer Composites - Processing of Thermosets Composites

15 Wet-lamination technique: Process variants Vacuum Bag Pressure Schraubzwinge Spannrahmen Dichtung gelochtes Blech Rinne für überflüssiges Harz Folie Verschraubung fester Deckel Druck Druckstutzen Druckfolie Verstärkung mit Laminat Trennschicht festes Werkzeugunterteil Überlauf umlaufende Dichtung Ventil zur Vakuumpumpe Laminat festes Werkzeugunterteil Vakuumbehälter für überflüssiges Harz Quellen: Ehrenstein, G.W.: Faserverbund-Kunststoffe, Werkstoffe-Verarbeitung-Eigenschaften; Carl Hanser Verlag, München 1992 Manufacturing of Polymer Composites - Processing of Thermosets Composites

16 Process automation example Scobalit AG, 8604 Winterthur Manufacturing of Polymer Composites - Processing of Thermosets Composites

17 Contents Introduction Wet-Lamination Process Flow in porous media Resin curing kinetics Resin viscosity Manufacturing of Polymer Composites - Processing of Thermosets Composites

18 Flow in porous media Pressure driven flow e.g. Processes: RTM, VARTM, VARI, etc. Capillary driven flow e.g. Processes: Pultrusion, filament winding, hand lamination, prepregging, etc. Darcy s law AK Q P Capillary number: Ca u cos Manufacturing of Polymer Composites - Processing of Thermosets Composites lv

19 Flow in porous media - Background Fluid In Fluid Out Porous Medium Darcy s law: Q AK P Fluid flow is dependent on: material permeability (K), fluid viscosity (μ), and driving pressure ( ) p Porosity is a function of compaction (required to adjust the fiber volume fraction of the composite) of the porous media Manufacturing of Polymer Composites - Processing of Thermosets Composites

20 Injection experiment in a glass tool Manufacturing of Polymer Composites - Processing of Thermosets Composites

21 Darcy s experiment piezometric tubes p1 g h 1 diameter D sand p2 g perforated plates h 2 Darcy s experiment (1856) Manufacturing of Polymer Composites - Processing of Thermosets Composites

22 Inside a composite: Computer Tomograph pictures highlighting the dual-scale nature of the porous media Meso-scale structure showing the bundles Micro-scale structure of the bundles showing the individual fibres within the bundles. Schell, J.S.U., Investigation of the Influence of Meso-scale Flow Effects in Liquid Composite Moulding Processes on the Laminate Quality, Diss. ETH Nr , 2007 Manufacturing of Polymer Composites - Processing of Thermosets Composites

23 Dual-scale structure is influencing the impregnation process Mode 1 of the impregnation model of woven fabrics Mode 2 of the impregnation model of woven fabrics Mode 3 of the impregnation model of woven fabrics C. Lekakou, M. G. Bader, Mathematical modelling of macro- and micro- infiltration in resin transfer moulding (RTM), Composites Part A 29 (1998) Manufacturing of Polymer Composites - Processing of Thermosets Composites

24 Fiber/Matrix interface development Fibre-wetting is a pre-condition for developing a good interface! M. Connor, Consolidation Mechanisms and Interfacial Phenomena in Thermoplastic Powder Impregnated Composites, PhD-Thesis No. 1413, EPF Lausanne, 1995 Manufacturing of Polymer Composites - Processing of Thermosets Composites

25 Capillary pressure Benetzung Wetting Keine No wetting Benetzung Gas phase (1) Gas phase (1) Liquid phase (2) Liquid phase (2) 0 Solid phase (3) 2 Capillary ascension Solid phase (3) 2 Capillary depression Manufacturing of Polymer Composites - Processing of Thermosets Composites

26 Wetting of Fibres Surface tension : dw da J m 2 kg 2 s N m Equilibrium condition: cos Capillary height: h 2 12 cos gr 3 13 Capillary pressure: P F A 2r cos 12 2 r 12 2cos r Manufacturing of Polymer Composites - Processing of Thermosets Composites

27 Contents Introduction Wet-Lamination Process Flow in porous media Resin curing kinetics Resin viscosity Manufacturing of Polymer Composites - Processing of Thermosets Composites

28 The processing time is depending on the rheology properties of the matrix 0,700 0,600 Viskosität / Pa*s 0,500 0,400 0,300 0,200 isotherm bei 50 C isotherm bei 90 C 0,100 0, Zeit / s Manufacturing of Polymer Composites - Processing of Thermosets Composites

29 Curing kinetics Addition polymerisation of epoxy systems is an exothermal reaction Q dt H ges Kamal-Sourour model: d dt k i T m n k k 1 1 A e i 2 Ei RT Coefficients can be extracted from DSC-curves! Manufacturing of Polymer Composites - Processing of Thermosets Composites

30 Contents Introduction Wet-Lamination Process Flow in porous media Resin curing kinetics Resin viscosity Manufacturing of Polymer Composites - Processing of Thermosets Composites

31 A simple viscosity model Viscosity model: (,T ) Ae B T C Castro und Macosko: (, T ) Ae B T g g C D With: A, B, C, D: Constants g : Curing degree of the resin at gelpoint Manufacturing of Polymer Composites - Processing of Thermosets Composites