Kaneka BMI material attains >25% lead time, >20% tool cost reductions in Janicki evaluations

Tooling is key to manufacturing composite parts but is often considered late in the production process.  Bismaleimide (BMI) prepreg has become the tooling material of choice for the manufacture of high-temperature composite structural parts due to its performance and durability, but there are still manufacturing challenges that typically impact cost and lead time. It was these challenges that Kaneka Aerospace (Benicia, Calif., U.S.) and Janicki Industries (Sedro-Woolley, Wash., U.S.) set out to solve.

Tooling challenges for composites fabrication

BMI tooling is required for composite parts cured at elevated temperatures where dimensional accuracy, thermal stability and long-term durability are critical. Whenever a part operates near heat sources or demands aerospace-level dimensional precision over a long service life, BMI tooling becomes essential to ensure part quality, repeatability and production yield. 

BMI composites have many advantages over other tooling options for the manufacture of composite parts, which come with their own constraints. Invar tools match the thermal expansion characteristics of carbon fiber composites and are very durable under repeated high-temperature cures, but the tools are heavy with high thermal mass and require considerable machining. Epoxy composite tooling is lower cost and can be used with low-temperature masters but lacks the durability for repeated high-temperature cures common in series production (see more in the sidebar below).

In addition to their light weight and low thermal mass, BMI tools have thus become the first choice for many production applications due to their ability to withstand repeated high-temperature cures. It is this feature, however, that also drives the need for high-cost master tools, which impacts tool cost and lead time. A further challenge in using BMI systems is off-gassing from the resin during 177°C tool cure, which causes degradation of standard nylon bagging film and the risk of vacuum loss during cure, requiring the need of alternate, more expensive bagging materials.

A BMI tooling resin system with lower initial cure temperature would fundamentally address these challenges. Thermodynamics still dictate that the tooling resin must undergo a high-temperature cure at some point to be capable of repeated part cures at 177°C, however, performing this off the master mold unlocks a new approach to the manufacturing process. Any new material must still meet current performance expectations including mechanical properties, toughness, durability, handling and out-time, while giving improvements in overall cost and lead time.

Kaneka Aerospace has long been a supplier to Janicki Industries for composite tooling products, which led to this collaboration. “The project was conceived in 2018 during a conversation between Janicki and Kaneka (then Applied Poleramic Inc.) about the challenges of curing traditional 177°C cure BMI systems,” says Jed Brich, R&D engineer at Janicki. “A nylon vacuum bag had recently failed during a large tool facesheet cure that was attributed to off-gassing of the BMI resin system.”

After multiple discussions, Kaneka Aerospace initiated a project to design a prepreg system that met Janicki’s needs and still had the tool durability of BMI well established in industry, but that could be cured — at least initially — at much lower temperatures.

Tooling prepreg evaluation, resin formulation iterations

Kaneka developed an innovative BMI chemistry designated TP2230 which has an initial cure on the master tool at 121°C, followed by a 204°C free-standing post-cure. This enables the use of lower-cost masters with considerable cost and lead time savings. Initial results were reported in a joint paper by Kaneka and Janicki at CAMX  2025.

“Developing the BMI polymer chemistry to achieve a sufficient degree of cure at 121°C so that the tool will be stable in the free-standing post-cure was quite a technical challenge,” reports Dr. Masaya Kotaki, senior director of product development, Kaneka Aerospace. “The materials also provide an out-time at shop conditions of at least 4 weeks which is important in the production of larger tools, and also standard layup, bagging and debulk methods can be used.”

Prepregs were evaluated with standard 2×2 twill weave, 6K carbon fiber tooling fabrics using T300 fibers from Syensqo (Brussels, Belgium) and AS4C fibers from Hexcel (Stamford, Conn., U.S.). Early development samples of this material were provided to Janicki in 2020. Preliminary test panels experienced challenges with tack and porosity. After a few quick iterations, Kaneka was able to tune the resin formulation which resulted in far better results.

Mechanical testing reported in the CAMX paper confirms that materials with both fibers achieve sufficient strength and stiffness after the initial cure and meet typical tooling performance requirements after post-cure.

Toughness is key to durability and resistance to cracking during repeated high-temperature cycling. Kaneka Aerospace evaluated interlaminar fracture toughness (G_ic) using a double cantilever beam test on TP2230 laminates containing both fibers. The results in Fig. 2 show that the toughness of TP2230 with both fibers is similar to legacy materials and increases after the post-cure. The G_ic of the material using Hexcel AS4C fibers is 20-30% higher than that using the T300 and this was investigated further by scanning electron microscopy of the fracture surfaces. These show fiber bridging and pullout accompanied by increased plastic deformation of the matrix in laminates made with AS4C, indicating high fiber-matrix adhesion. The tools show very good thermal stability with less than 1.2% weight loss after 10,000 hours (~14 months) ageing at 177°C (Fig. 2).

According to Dr. Leonid Vorobyev, principal scientist at Kaneka Aerospace, “The biggest challenge was balancing low temperature curability, tack-life and tool durability. BMIs that are curable at 121°C are very uncommon, so creativity was needed to achieve this. The further need to maintain a long tack-life, which typically is in a trade-off relationship with cure temperature, and the required thermal oxidative stability, was not simple.”

Manufacturing process evaluation: Simulated tooling cure

Following development and initial material testing, Janicki Industries performed manufacturing evaluations on the TP2230 tooling prepregs containing both types of carbon fiber using a “Z” spar tool with representative elements including opposing radii. Janicki’s observations concluded that the tack, drape and handling of TP2230 are comparable to legacy BMI tooling prepregs. The novel materials also have low bulk factor with minimal wrinkling and bunching after debulk, have suitable resin bleed during the initial 121°C cure and provide good surface finish after machining.

Janicki then used the demonstration tools in a simulated life cycle evaluation including environmental conditioning of 30 days in a clean room followed by layup of carbon and glass fiber prepregs and autoclave cure at 177°C (Fig. 3). The Hexcel AS4C tool has been evaluated for 84 cycles, and the Syensqo T300 tool for 137 cycles. Some localized surface fiber tearout was initially observed between cycles 20 and 30, with both fibers and the first observation of interlaminar cracks was at 40 cycles, which is typical of current BMI tools. Surface images and photomicrographs of the thermally aged spar tools (Fig. 4) confirm the high thermal stability and resistance to microcracking at elevated temperatures relative to legacy BMI tooling materials. Both tools continued to maintain vacuum integrity and the quality of parts cured on the tools remained high.

Janicki will continue cycling the small-scale test tools to at least 200 process cycles to assess the lifespan of TP2230 under realistic production conditions. Overall the tool using AS4C fiber shows improved durability, consistent with the toughness results.

Janicki has further evaluated the production capabilities of TP2230 through a 6.1-meter tool shown in the opening image (Fig. 1). Initial aerospace-quality parts are being molded on this tool to evaluate dimensional stability and performance of the tooling material at production-relevant scale and complexity. The company has already built multiple parts on the tool with thorough evaluation after each cycle and many more parts planned for the future. Additionally, Janicki has identified a large set of production tooling to be fabricated from TP2230 later this year.

Low-cure temperature BMI tooling prepreg for future programs

Kaneka and Janicki have noted that reducing the initial cure temperature from 177°C to 121°C allows the use of more economical master mold options. In addition, the lower initial cure temperature considerably reduces risk of vacuum bag failure during tool cure, as nylon vacuum bags are less prone to degradation and failure when exposed to BMI resin below 149°C.

Some of the specific benefits of the new tooling material seen by Janicki include 25-50% improvement in tool lead time and 20-40% improvement in tool cost.

“By combining reduced cure temperature with long-term thermal stability, TP2230 opens new opportunities for economical, high-performance tooling,” says Kotaki.

“The low-temperature initial cure of TP2230 enables us to streamline our tool manufacturing process, opening a pathway to reducing tooling costs and shortening lead times for our customers, while maintaining the high-temperature, high-durability performance that they demand,” notes Todd “TJ” Chace, senior director of R&D at Janicki. “Following our thorough evaluations, we have confidence that tools made with this material will produce high-quality parts for the life of most programs. Janicki will be producing the first string of production tools with TP2230 in early 2026 and continues to identify new opportunities for future customer programs.”