JEC COMPOSITES MAGAZINE - Issue #46 - January/February 2009 - 18

EQUIPMENT EQUIPMENT EQUIPMENT EQUIPMENT EQUIPMENT Mould High-temperature composite moulds produced by infusion The infusion process has been widely used in the composite industry but its use in mould making is relatively new. Composite moulds offer many advantages over their metal counterparts, notably their low weight and thermal expansion. Huntsman offers a new, easy method for making large composite tooling. he infusion process is quite old now. In 1950, Dr Muskat came up with the idea of connecting a tube to a source of resin and another to a vacuum pump. Then Dr Seemann created the SCRIMP process in the early 90s. Since 2000, many new processes have appeared such as LRI, CAPRI, VAP and RIFT to name just a few. The aerospace, marine, wind energy, construction and railway industries use this technology to produce aircraft parts (interior parts, primary parts), boat components (hulls, decks), turbine blades, bridge components (decks) and more. Huntsman is now using it to manufacture high-temperature composite tooling. T zed by a 100:50 mix ratio by weight, a 550 mPa.s viscosity at 25°C, a pot life of 18 or 6 hours at 25 or 35°C respectively for 100 g of mix, and a 190°C glass transition temperature as determined by dynamic mechanical analysis. Processing steps Master model For the first processing step (master model production), Huntsman recommends using the RenShape® BM 70, RenShape® BM 5460 or RenShape® BM 5055 board materials and the RenPaste® SV / HV 4503-1 or RenPaste® 4666 modelling pastes. Following conventional machining, the pattern has to be pretreated with 3 coats of release agent (QV 5110 paste) with a 15 minute pause before polishing and applying the next layer. mould surface. The gelcoat should be applied with a brush to achieve a layer with a minimum thickness of 0.3-0.4 mm. The gelcoat tack time is an important parameter that ensures a smooth finish. The right tack is achieved when you can touch the gelcoat and leave a fingerprint on it with no gelcoat on your finger. This way, the veil fabric will not print through. Tack life is about 24 hours which means is possible to work a full day on large parts. Lay-up A standard stacking sequence is used, with a veil as the first ply to avoid printthrough. This veil is generally a lightweight fabric under 200 g/m², weighing between 30 and 70 g/m². This is followed by several layers of carbon or glass fibre to reach a typical thickness of 4-5 mm according to the design calculations. A peel ply is then applied for subsequent removal of the A complex set of requirements A high-temperature composite tool needs to be durable and produced at a relatively low curing temperature, allowing for the use of cheap model materials such as polystyrene. At the same time, it needs to resist temperatures of 200°C, to exhibit a low coefficient of thermal expansion (especially for large parts), to have good impact resistance, and to comply with environmental, health and safety regulatory requirements. Combining all these contradictory needs is indeed a challenge. To meet infusion process requirements, the resin should have low viscosity, good wetting properties, a long pot life and allow for injection at room temperature, i.e. 23-25°C. Huntsman has developed a new resin system that complies with all these requirements: Araldite® LY 8615 + Aradur® 8615. The system is characteri- Gelcoat application The RenGel® SW 5200 + Ren® HY 5212 gelcoat is recommended for a smooth Veil layer (30-70 g/m²) Fig. 1: Lay-up. Carbon or glass fibre layers Peel ply Resin distribution medium Fig. 2: Infusion assembly. Infusion vacuum bag Curing vacuum bag 18 jec composites magazine / No46 January-February 2009

JEC COMPOSITES MAGAZINE - Issue #46 - January/February 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #46 - January/February 2009