Mould tools John Summerscales

Outline of lecture Tool design Tool materials Decision matrix Heating and cooling Lost cores Clamping Ancillary materials and systems

Tool design size, complexity and dimensional tolerances surface finish thermal expansion, conductivity etc holes, bosses and ribs inserts and fasteners re-entrants/multi-part moulds number of components to be produced durability, ease of modification and repairability

Tool materials Reductive manufacture (CNC machining) steel aluminium monolithic graphite syntactic foam (hollow microsphere composite) Additive manufacture wet lay-up glass reinforced plastics prepreg carbon fibre composite electroform nickel (EFN) backing structures Plastech MITTM Multiple Insert Tooling

Pre-preg/EFN tooling master splash tool HT male mandrel/bath master LTM tooling system omits this stage Female tool LTM tooling system omits this stage Tool with backing structure

Decision matrix: tooling options Nicholas Tiffin, "Choosing better tooling", Advanced Composites Engineering, Autumn 1988, 18/19. Note that the following analysis from Tiffin's paper is specific to a CFRP structural fairing P = Priority R = Rating V = Value (P*R)

Decision matrix: tooling options Steel Al Wet Lay Up Prepreg EF Nickel Critical parameter P R V Dimensional accuracy 10 7 70 6 60 8 80 100 Operating temperature 9 90 Temperature uniformity 4 36 5 45 63 Long tool life 72 1 64 Short cure cycle 3 18 24 54 Tool build time 30   TOTAL 340 337 329 452 418

Tracking barcodes or RFID inserts may be attached to mould tools to permit integration, e.g. with resin delivery systems, and automation.

Heating Cooling fluid in pipes embedded electrical heaters ovens and autoclaves Cooling

Embedded heaters 1 Thermion fabric Gorix ECT Plastech cotton/lycra heater cloth

Embedded heaters 2 PPM Solutions Plastech copper piping

Heating performance Comparison of cure cycle for 11 mm laminate on heated tool and in oven. The two temperature traces in each case are for the opposed laminate faces heated tool oven

Simulated temperature distribution Steady-state temperature distribution over tool (below) and laminate (above), for fixed heater temperature of 130°C Model = ¼ flat tool (symmetric).

Thermographic monitoring Infrared camera image of an electrically-heated tool-plate showing hot spots due to wrinkled heater cloth

Thermogram of electrically-heated mould tool 1 tool face during heat-up showing cool spots/lines corresponding to the thermocouple positions/wires and cooler outline at the resin-rich mould cavity lip

Thermogram of electrically-heated mould tool 2 tool face at target temperature of 90°C showing ~10°C variation across the component

Thermogram of electrically-heated mould tool 3 insulated back surface during dwell at 90°C

Thermogram of electrically-heated mould tool 4 tool back face (GRP side) without insulation showing the resistive heater element spacing (horizontal shading)

Lost cores rubber/elastomers [Musch and Bishop] inflatable mandrels [Musch and Bishop] low melting point alloys [Haines] candle or paraffin wax (melting points typically 50-90ºC) soluble salts or plaster (subsequently washed or machined out) Plastech SmartCore (granules enclosed in a shaped vacuum bag)

Clamping bolts hydraulic press vacuum labour intensive, low pressure capital equipment, good alignment vacuum inexpensive, limit ~1000 mbar, sealing issues

Ancillary materials and systems mould release (coatings and films) bagging films (1-sided moulds) breather and bleeder cloths (vacuum bag) flow media (infusion) tacky tape - edge dams - breach units pressure intensifiers preforming supports

Acknowledgements the respective companies for illustrations of the embedded heaters Dr Stephen Grove for the performance graph and simulation Dave Nelson of FLIR Systems Limited for wrinkled heater cloth thermograms Scott Foster of Metrum Information Storage Limited for skeg thermograms