PROBLEM – How to fabricate a flight quality co-cured I-Beam composite structure in an environment that enables high
OPPORTUNITY – Generate a viable solution that will produce a high quality composite with an accelerated curing cycle using Smart Tools that act as bladders during cure.
SOLUTION – A PLC controlled, self-heating, and self-pressurizing cure mold was combined with three (3) Smart Tools that act as bladders during cure to create a NDT verified, high quality composite I-Beam with a 50% reduction in cure cycle versus the autoclave cured baseline.
One (1) three Cavity Smart Tool Master/Reforming Mold, three (3) Smart Tools that act as bladders during cure, One (1) PLC controlled self-heated and self-pressuring Cure Mold.
Smart Tools are made from a combination of Shape Memory Polymers (SMP) and trade secret continuous fibers that allow them to transition from being rigid at room temperature to highly elastic, like a balloon, when they are heated above their activation temperature. For this case study the Smart Tools act like bladders during cure. They are rigid for lay-up, they are elastic and apply compaction force onto the composite laminate during cure, and they are elastic for a low force extraction from the cured composite part. Smart Tools are durable and reusable, with typical cycle life of 50 – 70 cycles, and deliver improved quality, reduced labor and consumable cost, and higher
Method of Manufacture
This case study was focused on proving the feasibility to use Smart Tools that act as bladders during cure, combined with an out of autoclave and out of oven curing solution, to produce a high quality, co-cured I-Beam composite structure.
Smart Tools were made to the Net Inner Mold Line (IML) of the composite I-Beam and had a shrink wrapped release film applied to them. The Smart Tools acted as rigid mandrels for hand applied pre-preg lay-up that was de-bulked every three (3) layers. A total of seventeen (17) layers were applied.
Skin pre-preg plies were placed into the lower half of the self-heated, two (2) cavity, female cure mold followed by custom molded noodles that fit in between the Smart Tools. The Smart Tools are laid up with many plies of re-preg and loaded into the lower half of the cure mold, side-by-side. Custom molded noodles are placed between the top of the Smart Tools to create a flush top surface and pre-preg skin plies are applied to the top surface.
Vacuum bags were then pulled through the center of the Smart Tools and after the upper cure mold cavity was put in place, the vacuum bags were sealed to the outside ends of the mold with bag tape. End fittings were applied on each end of the cure mold to create a pressurizable environment. The cure mold is heated by a combination of cartridge heaters and a forced air heater. Pressure is supplied by heated shop air serviced by a shop wide compressor.
The automated cure mold was turned on and ran a specified cure and pressure profile. Initially vacuum was applied to the cavity and once the temperature exceeded 160°F (71°C) vacuum was stopped and the vacuum bags were inflated with 85 psi (≈6 Bar) that in turn, pressurized the now elastic Smart Tools to apply nominal pressure on the underside of the composite laminate and against the inside of the cure mold to force out air and excess resin.
Post the cure cycle and while the mold temperature was still above 160°F (71°C), the Smart Tools were removed from the cured composite and placed into a pre-heated reforming mold (the same mold the Smart Tools were made in), vacuum bags were run through the Smart Tools and taped to the outside of the mold, vacuum was applied to reset the Smart Tool to its original geometric shape, and once the mold cooled the Smart Tool was ready for making the next composite I-Beam.
Co-Cured I-Beam Results
The I-Beam has the same structure as many unitized, co-cured, multi-chamber composite parts, like a horizontal stabilizer, a blade spar, or a winglet. The actual composite I-Beam produced had shear webs that were within 0.007” of nominal, flight quality void content and a 50% reduction in cure cycle versus the autoclave cure baseline.
Smart Tooling provides formable, reusable tooling solutions for manufacturing composite parts with complex geometries for the aerospace & defense industry. Smart Tools improve quality, reduce labor hours, decrease consumables, and increase throughput – essentially, Smart Tools enable the manufacturing of composite parts better, cheaper, and faster.
Smart Tooling’s Shape Memory Polymers are designed to be aerospace-grade RIGID epoxies at room temperature, and highly FLEXIBLE elastomers when heated, eliminating the need for expensive, laborious, tedious, dirty, and challenging solutions such as melt-out foam, metal breakdown tools, rubber bladders, or washout tooling.
We also deliver comprehensive solutions. We offer total solutions for the manufacture of your composite part, including custom tooling engineering and design, fabrication of molds, Smart Tooling fabrication, initial composite part manufacturing, custom standard operating procedures, onsite start-up support and training, and any future training if required.
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