First 250°F BMI ply after debulk to fiber-reinforced polymer (FRP) master. Source| Kaneka Aerospace

Kaneka Aerospace (Bernicia, Calif., U.S.) is co-presenting with Janicki Industries (Sedro-Woolley, Wash., U.S.) composite tools that have been developed using a novel bismaleimide (BMI) prepreg that achieves reduced cost and lead time without sacrificing performance. 

The company’s novel BMI prepreg imparts several notable features: 

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• Optimal thermal oxidative stability makes it resistant to microcracks and weight loss is less than half of legacy BMI tooling prepregs
• Demoldable after initial cure at 121°C (250°F)
• Uses technology that enables thermal stresses to be relieved during thermal cycling while maintaining shape.

After successful fabrication and evaluation of the flat tooling plates, new tools using the BMI prepreg were fabricated. These tools included stringer-like geometry to evaluate the effects of ¼" and ½" concave and convex radii on laminate quality. Elevated temperature debulks were used periodically to remove bulk and inspect laminate quality over radii. The tools were consolidated and cured in an autoclave and then freestanding post-cured in an oven using cycles provided by Kaneka. Samples were taken after each cure for microscopy.

The tools were machined using the same parameters and end mills as used for 350°F cure BMI tooling prepreg, followed by sanding to remove mill scallops and achieve surface roughness typical for aerospace composite tooling.

The BMI tools are capable of being cured initially at 121°C (250°F) followed by a 204°C (400°F) cure in a freestanding manner. Simulated life cycle testing of 250°F BMI shows similar durability when compared with industry standard 350°F cured BMI tooling prepregs. The ability to cure BMI at 250°F, Kaneka reports, allows for significantly more material options to rapidly produce economical patterns or “direct masters.”

Kaneka Aerospace specializes in high-performance composite materials for the aerospace and industrial markets. Its prepregs, resins and adhesives provide distinguishing properties that enable customers to achieve value beyond lightweight and strength.