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FEATURE: Automotive Composites Source (both photos) | AGFM press, it causes areas of high fber stress, he explains. Tose fbers have a tendency to relax, or spring back, to relieve the stress, which results in an improperly sized preform. "Te preform tooling must be designed to compensate for springback, and achieve 'overforming,'" he says. Overforming refers to pressing the fabric beyond the actual part dimensions in deep draw areas, on the order of a few millimeters, so that when the preform springs back slightly, it conforms to the desired part dimensions. "Tis is why you should not make preforms in the actual part molding tool," Buckley advises. "When springback occurs — because the tool isn't optimized for overforming — the preform will be too small." Another big consideration is ensuring that the material used to bind or hold the preform in place during the forming process is compatible both with the sizing used on the fbers and the resin that will infuse them. Reported problems include thermoplastic binders that repel thermoset molding resins, resulting in weak resin/fber bonds, and binders that "wash" and rise to the preform surface when it is inserted in a hot tool, causing fnished part defects. In recent years binder suppliers have developed binders that crosslink and cure with the matrix resin. AGFM ofers thermoset binders, for example, designed to work with fber sizings and to be chemically compatible with thermoset molding resins. Machine and process refineMent A preform demonstrator part is shown in the mold (above), after shaping by a forming template. The photo at right shows the preform, held in shape by a lightcurable binder, after it was shuttled into position under highintensity lamps, to cure in 17 seconds, well within automotive part production cycle times. ADHESIVES AND SEALANTS BONDING COMPOSITES, THERMOPLASTICS, METALS AND DISSIMILAR SUBSTRATES ADVANCED FOR Equipment and materials suppliers have spent many years developing a variety of preforming methods. AGFM, for one, ofers its fast CompForm process, which employs a proprietary light-curable binder. Billed as curable in less than 20 seconds, the binder, claims Buckley, has the potential to cure as quickly as one second, if the preform shape and complexity permits. Te binder works on optically transparent materials, such as fberglass engineering fabrics and mats, and it can even cure through some lightweight foams and hybrid glass/carbon materials. Te binder is produced by Zeon Technologies Inc. (Salisbury, N.C.) and consists of a resin backbone that can be functionalized A PIONEER AND LEADING MANUFACTURER OF INNOVATIVE SPRAYABLE SYNTACTIC MATERIALS AND SPRAYABLE INDUSTRIAL COATINGS · Sprayable fller/primers for use on many substrates · Ease of use 24 · Sprayable coring materials and barrier coats · High impact resistance, fexibility, and durability compositesworld.com · Over 30 years of application experience · Polyester adhesive putties for flling and bonding · Reduced cycle times · Patented MMA technology and service · Sprayable mold and plug building materials · Brushable and sprayable radius materials Plexus® and SprayCore® adhesives, sealants and sprayable syntactics... improve product quality/durability while increasing manufacturing effciencies and reducing VOC emissions!!! Plexus® brand is proud to be certifed by... www.itwadhesives.com