Hybrid molding process and material innovation deliver 60% weight saving

Victrex (West Conshohocken, PA) has developed a new polyaryletherketone (PAEK)-based polymer and an innovative hybrid molding technology that enable overmolding of a PAEK-based composite with fiber-reinforced Victrexpolyetheretherketone (PEEK) injection molding grades.

This development reportedly allows the design of stronger, lower cost components that are up to 60% lighter than typical metal and thermoset systems. By working together, Victrex and Tri-Mack Plastics Manufacturing Corp. (Bristol, RI) have engineered an aerospace bracket using this new polymer and technique with the demanding performance requirements of loaded applications in mind.

Aerospace bracket is molded in hybrid insert-molded using PAEK and PEEK materials.

The hybrid process uses a pre-formed composite like an insert in the injection molding tool. The PAEK-based composite is thermoformed prior to insertion. Traditional hybrid processes require a continuously-reinforced thermoplastic composite to be pre-heated to very high temperatures which generates additional costs and processing challenges. The new hybrid process that Victrex has developed allows the continuously-reinforced thermoplastic composite to be pre-fabricated and used in the same manner as a metallic insert in the injection moulding process.

The new PAEK-based polymer allows for continuously-reinforced thermoplastic composite (70% fiber loading) processing temperatures that are approximately 40°C (72°F) less than traditional Victrex PEEK-based composites. This reportedly creates a very strong bond between a continuously-reinforced thermoplastic composite and an injection-molding polymer. The polymer also possesses an optimal crystallinity level which helps deliver excellent mechanical and temperature properties as well as chemical resistance according to Victrex. The lower processing temperature also enables faster manufacturing cycle times and the use of existing equipment designed for lower temperature materials (PPS, PEKK).  Most importantly, it allows for the overmolding of Victrex PAEK-based continuously-reinforced composites with filled Victrex PEEK polymers in a cost-effective, insert-molding type process. The PEEK polymers can be either carbon fiber- or glass fiber-reinforced grades, typically with fiber loadings of 30-40%.

The development of technologies for the aerospace industry is making significant progress not only from a material perspective, but from a processing standpoint as well according to Victrex. Engineers are requiring lightweight, complex parts at lower costs, higher processing efficiencies, and improved mechanical properties. This can reportedly be delivered by using the hybrid molding process.

Commercial aircraft use thousands of brackets from the cockpit to the tail of the plane. The total amount of brackets on an aircraft can add a significant amount of weight especially if they are made from metal. The hybrid-molded Victrex PAEK-based composite bracket is able to deliver up to 60% weight savings compared to stainless steel and titanium while offering equivalent or better mechanical properties such as strength, stiffness, and fatigue. "These technologies are enabling engineers to design lighter, stronger and more cost-effective solutions like the new bracket," stated Tim Herr, Aerospace Strategic Business Unit Director for Victrex. Herr says, "This game-changing advantage over metals and thermoset composites is a result of our dedication to the future of flight."

Tri-Mack has a long-standing relationship with Victrex in the development of high-performance aerospace components using PAEK polymers. "Given our expertise in the industry, we were excited to use a new polymer and process to develop an innovative product," said Tom Kneath, Director of Sales and Marketing for Tri-Mack. Kneath added, "The design flexibility of the materials, along with the technical support from Victrex, enabled us to engineer and manufacture a PAEK bracket that can be produced in minutes compared to the hours it would take for a metal or thermoset equivalent."

This improvement in manufacturing efficiency translates into less processing time, lower energy requirements, and reduced waste for Tri-Mack. Those benefits, paired with eliminating steps such as edge sealing and X-ray inspections, help to reduce overall part costs. The benefits are not only limited to aerospace designs. The overall mechanical properties, weight savings, and processing efficiencies offer a step-change for the automotive, energy, and consumer electronics industries as well. 

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