Swapping Metal for Thermoplastics Speeds Prototyping

In the race to bring new eVTOL aircraft to market, advanced air mobility start-ups face the challenge of making rapid progress toward type certification while containing costs. Building and reworking prototypes is part of this equation, and composites specialist Greene Tweed says it is helping by cutting lead times in half. The company aims to have its materials and processes used for new production models.

At the Farnborough International Airshow, the U.S.-based group is demonstrating breakthroughs such as how its Xycomp DLF—a discontinuous long fiber (DLF) thermoplastic—is being deployed to provide rapidly changeable prototype tooling for composite parts. According to the company, this approach allowed an undisclosed defense industry partner to rework a prototype in just over seven weeks, compared with 16 to 20 weeks said to be more typical with traditional methods. For another project, the company produced more than 400 parts from a single modular prototype run.

Greene Tweed’s engineering team focused on diversifying applications for its composite manufacturing process during the commercial aerospace slowdown triggered by the Covid pandemic. It is now active in supporting several eVTOL aircraft programs, as well as clients in the defense, mobile robotics, and automotive sectors.

Thermoplastics Replace Metal

Xycomp DLF is a line of long-fiber thermoplastic products designed to replace metals with weight savings of up to 60%. Using ProFusion compression molding techniques has allowed Greene Tweed to produce assemblies with fewer parts for a product range that also includes seals, bearings, and rings.

A partnership with GE Aerospace’s GE Unison division has delivered a different approach to making engine build-up brackets, which position and support mechanical and electrical components in aircraft engine cores and fan cases. Greene Tweed was challenged to design and make brackets that can withstand vibration, temperature fluctuations, and abusive loading while also resisting damage from engine fluids. It says that the brackets made for series production with unidentified engine manufacturers have resulted in an 86% weight saving compared with metal alternatives.

According to Greene Tweed, the approval process for the brackets was rigorous and involved a comprehensive test program with GE Unison. The tests simulated critical functional requirements for the brackets and included insert torque, pull-out, and loading exercises.

Using simplified mold design and other process improvements, Greene Tweed has been able to complete precise mold fit-ups for products in just one or two days. Part of the accelerated production process has come from combining CNC programming with simultaneous tool manufacturing. “This entire process is iterative, enabling customers to test and refine components quickly and cost-effectively,” the company said.