CompositesWorld
Issue link: https://cw.epubxp.com/i/630867
12 OUT OF AUTOCLAVE SUPPLEMENT » A strong advocate of thermoplastic composites, David Hauber, VP of Engi- neering at Automated Dynamics (Sche- nectady, NY, US), is working diligently to dispel what he calls the "myth" of the necessity for <1% porosity (void content) in composite aerostructures. "Te key is not porosity," he contends. "It's performance. Tough thermoplastic materials are much less sensitive to porosity than their more brittle ther- moset counterparts." For proof of this, Hauber points to work Automated Dynamics has done developing a thermoplastic driveshaft for helicopter use that ofers a 35% weight reduction compared to its aluminum predecessor, with 150% post-ballistic torque to failure — all with 4% porosity. Te project was funded by a Navy Small Business Innovation Research (SBIR) Phase II grant that partnered ADC with SURVICE Engineering (Belcamp, MD, US) and UTC Aerospace Systems (UTAS, Rome, NY, US). Te driveshaft is composed of a carbon fber/ polyetheretherketone (PEEK) prepreg that features HexTow IM7 fber, from Hexcel (Stamford, CT, US). Te prepreg is in-situ placed via an automated fber placement (AFP) system developed by Automated Dynamics, on a cylindrical aluminum mandrel. Te system's short heat-afected zone and high pressure applied at laydown produces a shaft that is immedi- ately and fully consolidated, with, says Hauber, no post-process work required to fnish cure. After consolidation, the shaft is removed from the mandrel, trimmed and sent to UTC Aerospace Systems, where end-fttings are added and testing begins. Te shaft's key performance metric is how it responds in a ballistic environment, and this, says Hauber, is what led the customer to thermoplastics in the frst place. "Te initial impetus for going to ther- moplastics for this shaft was for better operational durability," he points out. To assess the ballistic response, SURVICE simulates what Hauber says is considered the worst possible damage a shaft might endure: a glancing blow from a high-speed projectile. Te shaft is then tested to failure in a damaged state; the Automated Dynamics shaft, reports Hauber, failed at 150% of the required value. Feedback has been very positive; the next step will be testing the shaft in an operational environ- ment, with a goal of TRL 6. Hauber acknowledges that thermoplastic compos- ites advocates have a long row to hoe convincing the aerospace industry that product performance trumps porosity values. Tis is particularly challenging given the long qualifcation cycles a material must endure before it is approved for commercial use: "It's very expensive to characterize and qualify a new material," he says. "Te challenge is to overcome the perceived risk by demonstrating improved performance in a demanding operating environment." OOA: Thermoplastic alternative targets performance spec CF/PEEK helicopter driveshaft's toughness trumps traditional metric. By Jef Sloan / Editor-in-Chief Thermoplastic composites: Toughness triumphs Development of this helicopter driveshaft helped dispel the notion that porosity is paramount when it comes to thermoplastic composites performance. It ofered a 35% weight reduction compared to its aluminum predecessor, with 150% post-ballistic torque to failure — with thermoset-unacceptable 4% porosity. Source | Automated Dynamics