Fabricating composite parts with complex shapes not easily removed from an inflexible mold—called trapped tooling—is traditionally an arduous process. Traditional, multi-piece "jigsaw" mandrels must be painstakingly disassembled from the inside after the composite part has been cured. Wash-out mandrels are messy and cannot be reused, and silicone mandrels are often expensive and can only be used a limited number of times.
CRG came up with a new solution to this problem, called Smart Tooling, using shape memory composites. Mandrels created with shape memory polymers (SMPs) combined with specialized reinforcement materials can be heated above their transition temperature, inflated inside a clamshell mold, and cooled until they become rigid and hold their new shape. A composite part is then laid up on the molded mandrel tool, and the assembly is heated enough to cure the part without reactivating the SMP. Once curing is complete, the entire assembly is heated above the SMP's activation temperature. The mandrel becomes flexible and returns to its original narrow tube shape, making it easy to pull away from the part and remove.
Shape memory polymers can be engineered with a wide range of transition temperatures, but some composite parts either require a precision interior finish or need a curing temperature higher than the highest transition temperature SMP. To meet these needs, CRG also developed a bladder variation of SMP mandrels.
Some benefits of Smart Tooling include faster fabrication, reduced cycle time, reduced material and mandrel creation costs, reduced labor costs, simple extraction process, reusability, lower environmental impact, cleaner process, and tremendous shape versatility.