Addressing key challenges in composite AM for maritime parts

Yannick Willemin, Head of marketing & business development, 9T Labs AG

For millennia, wood has had a very strong relationship with shipbuilding. Among its benefits, wood is both natural and usually locally sourced while offering very-high performances in harsh marine environments. Another beneficial property is that wood is anisotropic, meaning its properties vary in different directions (e.g., it is stronger along the grain than across it).

While wood is still used in modern shipbuilding, many other materials have since made their appearance, including metals, polymers, and composites. As in other fields, the racing segment provides glimpses of how ships could be made in the future. In America’s Cup, considered the Formula 1 on water, most parts are manufactured out of carbon fiber-reinforced composites.

However, while composites are found in larger boat components like hulls, masts, sails, foils, etc., metal still dominates in smaller, thicker, more complex parts – regardless of whether the boat is for racing, shipping, or leisure.

• Practical fiber-placement limitations with continuous-fiber composites
• Resolution in machined composites
• Challenges accurately predicting performance of discontinuous-fiber composites

These three factors lead to lower repeatability and reproducibility (R&R) values and higher costs – particularly with smaller parts produced at lower volumes – limiting usage of these materials in applications where they could be quite useful.

To solve these challenges, the new Additive Fusion Technology (AFT) developed by 9T Labs combines the resolution and unmatched design freedom of 3D printing with the performances of compression-molded continuous-carbon fiber composites. The hybrid AFT platform produces precision structural parts in continuous carbon fiber-reinforced thermoplastic composites (including PEEK, PEKK, PPS, PA12) in small to medium size (printer build envelope 350 x 270 x 250 millimeters) for low to medium volume production (100 to 10,000 parts/year).

Uniquely, the technology combines 3D printing – done in the Build Module layup/preform machine – followed by consolidation and forming in the Fusion Module compact compression press with matched–metal mold. The final parts also offer 100% traceability.

The system produces parts with higher complexity achieved with greater design freedom, the ability to insert hardware to reduce finishing, plus finer fiber-orientation control than other continuous-fiber layup/forming processes. Scrap rates are greatly reduced since parts are printed near net shape. Exclusive focus on thermoplastic matrices brings:

1. fast cycle times
2. recyclability
3. the ability to join smaller components into larger, more complex modules via welding

Excellent surface finishes, low voids, and high R&R are accomplished by consolidating/forming in metal molds.

Additive Fusion Technology permits cost-competitive manufacturing in part sizes and production volumes typically hard to achieve in structural carbon composites. Initially, design opportunities that reduce weight and cost while increasing performance of marine equipment are being targeted. Suitable parts already identified include headboards, V-block, CRX rollers, and winch handles. In the case of headboards, the benchmark material is aluminum. With AFT, part weight can be halved (from 1.05 kg to 0.55 kg) at competitive cost.

Finally, in addition to optimizing mechanical properties at lower mass and cost, another benefit of producing composite parts via additive manufacturing is the opportunity to apply surface layers with unique aesthetic functions.