Cornerstone Research Group, Inc. (CRG) has demonstrated the feasibility of filament winding complex-curved composite shapes on shape memory polymer (SMP) mandrels. SMPs can exhibit a radical change from a rigid polymer to a flexible, elastic state, and then back to a rigid state under thermal stimuli. SMP mandrels for filament winding and fiber placement allow for a quick, easy, reusable, and low-cost mandrel system. CRG has recently improved the SMP mandrel technology by adding a high-strain fiber reinforcement (HSFR) that both raises the toughness of the SMP and allows the SMP to elongate up to 150 percent. The resulting material can produce mandrels durable enough to withstand multiple use in high production rate manufacturing. This paper will demonstrate and discuss the feasibility of HSFR-SMP mandrels for filament winding and fiber placement and recent developments in CRG's SMP mandrel technology, including the fabrication of larger parts.
Cornerstone Research Group, Inc. (CRG) has recently demonstrated the feasibility of filament winding complex compound-curved composite shapes on shape memory polymer (SMP) mandrels. Under thermal stimuli, SMPs can exhibit a radical change from a rigid polymer to a flexible, elastic state, and then back to a rigid state again. SMP tubes were fabricated using CRG's Veriflex, a thermoset SMP resin system. The SMP tubes were raised above the transition temperature, the temperature at which the SMP becomes pliable and rubber-like and inflated inside a clamshell master metal mold with a cavity in the shape of the desired mandrel. The SMP was then cooled; the lowering of the temperature allows the SMP to become a rigid structure again, resulting in an exact replica of the cavity without the need of air pressure. A composite part was filament wound onto the SMP mandrel and after curing of the composite, the SMP mandrel is again raised above the transition temperature. This allows the mandrel to return to its memory shape for easy extraction. This paper will demonstrate and discuss the feasibility of SMP mandrels for filament winding and fiber placement composite manufacturing techniques allowing for quick, easy, and low cost mandrels that are dimensionally accurate, autoclave-tolerant, rapidly removable, and reusable .
Advances in earth and space instrumentation will come from future optical systems that provide large, deployable collecting areas of low areal mass density (< 10 kg/sq meter), affordable costs of fabrication ($10k/sq meter), and production times of a few years or less. Laminated optics comprised of an electroformed, replicated nickel optical surface supported by a reinforced shape memory resin composite substrate have the potential to meet the requirements for rapid fabrication of lightweight, monolithic, stowable, large optics, where large is defined to be 8 meters in diameter or larger. The high stiffness of a deployable composite substrate and a high quality, thin, electroformed metal optical surface combine the best properties of these disparate materials to provide a robust yet lightweight mirror system to meet the needs of future missions. The unique properties of shape memory resins in the composite provide a larger range of design parameters for production of usable optics. Results are presented from optical and structural tests of various surface and substrate constructions that may be solutions to the key issues, which are primarily material interface stress control, stability, and deployment repeatability. Initial requirements analysis and material properties measurements that determine both system and individual material target performance are presented.
Cornerstone Research Group, Inc. (CRG) has developed processes to make molds for casting and mandrels for filament winding composite parts from novel shape memory polymers (SMPs). For external molding, the SMP tooling system is capable of being thermally formed into a precise negative image of a master part, cooled, and made to retain the new shape. For filament winding mandrels, internal SMP mandrels can be used and easily extracted after curing. CRG has developed the ability to fabricate SMP materials from a wide range of polymer systems. Veriflex, the trademark name for CRG's shape memory polymer resin systems, functions on thermal activation customizable from -20°F to 520°F. These materials can withstand the elevated temperatures that are needed to cure composite parts without deformation and offer a gentle, simple demolding process. After the composite part has cured, the mold is raised above the Tg, which allows it to retract to its memory shape. SMP tooling processes provide the opportunity to mitigate the drawbacks of traditional fabrication techniques for advanced composite parts. This tooling system also possesses versatility in size variations, including being capable of micro (nanometers) to macro (meters) replication.