Prepregs curing

Dwell time Time required to equalize tool and component temperatures and to initiate controlled prepreg cure. 

A thermal cure hot melt phenolic resin providing adequate stability and viscosity and developed for the manufacture of aerospace prepregs. Cured glass composites (60 minutes 135 C) demonstrate excellent flexural, tensile and compressive properties. The resin can be modified with GP413D41 and GP464D20 elastomeric modifiers to produce composites with improved toughness while maintaining superior fire resistance and low smoke density. 

Figure 7.28 Polyester prepreg cure at the isothermal temperatures shown. Modulus and damping...

Blends have also been prepared by dissolving DMPPO in a monomer and then polymerizing the monomer. An example is an epoxy—DMPPO blend prepared by curing a solution of DMPPO in Epon 828 at 85°C with an alurninum—tetramethylguariidine catalyst. Some copolymer formation is observed. The solutions can be appHed to glass cloth before curing to produce prepregs for composites in appHcations such as printed circuit boards (67). 

The resin system V-378A, mentioned eadier, is a bismaleimide system that has been modified with divinylbenzene to achieve drape and tack in prepreg form. Divinylbenzene-modifted BMI is appreciated because of its outstanding hot—wet environmental resistance and epoxylike cure (18). 

PMR-15, the prepreg is B-staged to remove condensation volatiles and subsequently cured to yield dense composites with good high temperature properties. LARC-160 is also available from several prepreggers. 

StructurPly I and II by Multi-Axial are thermoplastic matrix resin prepregs used in the construction of primary-load-carrying composite structures. Unlike the few hours typically required by the thermoset resin materials to cure, StructurPly needs a few minutes at 196°C. 

Fiber tows are impregnated with Epon 828 (cured with m-phenylene diamine) and the prepreg cut into plies and compression molded, with 16 plies to a composite. Thin Teflon strips are inserted between plies 8 and 9 prior to molding, which initiate an interlaminar crack when the bar is loaded as a double cantilever beam. 

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