JEC COMPOSITES MAGAZINE - Issue #46 - January/February 2009 - 19

distribution medium (Figure 1). The lay-up for the infusion process consists of a resin distribution medium, an infusion vacuum bag and a curing vacuum bag. The second vacuum bag is added for safety purposes seeing that the gel time is about 24 hours (Figure 2). More information About Huntsman Huntsman Advanced Materials is part of Huntsman, a global manufacturer and marketer of differentiated chemicals. Huntsman has 13,000 employees and operates from multiple locations worldwide. The company had 2007 revenues of approximately $10 billion. Huntsman Advanced Materials is a pioneer and marketer of formulated materials for tooling, casting, encapsulation, composites, stereo-lithography and adhesives, and serves over 4,500 customers in more than 90 countries. The company’s 2,200 employees generated revenue of $1,396 million in 2007. Huntsman Advanced Materials is a leading supplier in key markets such as aerospace, adhesives, automotive, coatings and construction, power, wind, electronics, stereo-lithography, as well as sports and leisure. Infusion, cure, stiffening and postcure A common process is also used at this stage. Araldite® LY 8615 and a hardener (100:50 weight ratio) are mixed together and degassed. After infusion, the inlet and outlet of the first vacuum bag are closed once all the fabrics have been impregnated. As previously mentioned, the second vacuum bag is used to avoid any leakage from the first bag. A vacuum is maintained in this bag. The system is cured at 40°C for 24 hours and then carbon stiffeners can be bonded with a silicone adhesive to assemble the backing structure. The part is then demoulded (Figure 3) carefully since it is not totally cured: decohesion between fabrics can appear if a hammer is used. A post-curing step is necessary to ensure that the future composite tool has all the required properties. The temperature is increased from 40 to 180°C with a dwell of 2 hours every 20°C. The tool is then maintained at 180°C for 5 hours, followed by a reverse cooling step. The complete cycle lasts 35 hours (Figure 4). Fig. 4: Post-cure cycle. Combining a slow temperature rise and a long curing time ensures low distortion, no deviation, and no internal stress in the tool or master model. Conclusion The infusion process offers many advantages over wet lay-up, including safer working conditions (no VOC emissions), a lower porosity content, and greater reproducibility as the mould quality depends less on worker skills. Infusion also has many advantages over prepregs in terms of processing time, equipment (autoclave), storage and supply chain (prepregs have to be stored frozen), and cost-saving (about 30%). Part production A semi-permanent release agent capable of withstanding temperatures over 200°C is recommended for tool preparation, with the treatment being repeated every 10-15 parts. Huntsman expects this new type of composite tool to reach a production of 300 parts. If necessary, the following repair procedure should be used: abrasion of the defect areas, cleaning (grease and dust) to ensure good bonding, application of the mixed gelcoat, and post-curing under conditions similar to those applied for part production. Fig. 3: Demoulded tool. More information: www.huntsman.com/aerospace Contact: panayota_tsotra@huntsman.com No46 January-February 2009 / jec composites magazine 19

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

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