design and manufacturing development of thick
TRANSCRIPT
Design and Manufacturing Development of
a Thick Composite Rotor Component
Pin Lin “Ben” Chiou and Mark Wiinikka Engineer V
Manufacturing Research and Rotor Design
Overview
• Main Rotor Grip of Bell’s 525 • Design and Manufacturing Considerations • Design and Sub-Scaled Article Development • Full-Scaled Article Development • Process Automation
525’s Main Rotor Grip
The main rotor Grip is a highly loaded structure connecting the rotor blade to the rotor hub
An U-channel with two arms and a turn-around
Design Considerations • Structural attachments of CF bearing, pitch horn, lead-lag damper, flapping stops and rotor blades • Clearance requirements (turn-around size)
• Aerodynamic drag (blade root size) • Damage tolerance
• Twisted shape to simplify blade geometry
• Parallelism between two arms and inside profile of turn-around
• Laminate quality and consistency (no fiber distortion)
• Weight (drop plies outside blade attachment area)
Manufacturing Considerations • An U-channel structure is subjected to Spring-In
• Turn-around area is prone to out-of-plane fiber distortion
• Thickness transition area prone to out-of-plane fiber distortion • Twisting or IML thickness taper adds complexity to layup and tooling • Machined features on IML increase tooling complexity and difficulty
Tool angle 4.6° Part angle 1.6° Part angle 1.9°
Out-of-plane fiber distortion
Sub-Scaled Article Development
• IML tool; utilized low cost tool • Materials and forms – fiberglass or carbon; combine +/-, double thick • Lay up sequence – ply pack or dispersed • Lay up process – hand lay-up; pressure/tension in turn-around; automation • Compaction cycles – bulk reduction required prior to cure • Cauls – accommodate turn-around • Thickness change; cure cycle; spring-in
• Preliminary testing; cured laminate characteristics; tool compensation factor
Design Evolution
Preliminary • Glass or carbon construction • Tapered IML and OML surfaces • Ply pack lay up sequence • Large areas of co-cured sacrificial material for machining
In-line Twisted
Optimized • All carbon construction • Constant thickness • Dispersed lay up sequence • Secondary bond of small areas for machining
Full Scaled Article Development
• Adjustable full scaled test tool with a tool compensation factor from sub-scaled development
• Vacuum compaction cycles were time consuming • Number of vacuum compaction cycles needed depends on the limited manual lay up pressure applied
Full Scaled Article Development
• Finalized laminate thickness, ply orientation
• Finalized compaction cycles, cauls, cure cycle
• Finalized NDI development
• Double-wide blank for two parts at a time
• Detool fixture, machining fixture, bond assembly fixtures
Lay Up and Compaction Automation
• Hand lay up was the baseline process • Automating the lay up and reducing vacuum compaction cycles will significantly reduce the cycle time
• Conceived and designed a machine for automated lay up Critical process parameters was the roller application
• Can be fully automated if desired
Lay Up and Compaction Automation
Full Scaled Fatigue Test Article
• Test article fabricated with imbedded flaws in critical regions
• Fatigue tested to two life cycles (25,000 hours each) of Ground-Air- Ground loads • Test article also subjected to impact damage in critical areas
• Test article endured
The development of a thick composite rotor component was successful considering both design and manufacturing
Conclusions
• Early consideration of both design and manufacturing are critical
• Utilization of the sub-scaled test article was efficient
• Design and manufacturing are both critical to the success
