Composite Aircraft: How to Make Airplanes Out of Cloth

1 Aurora Flight Sciences Aurora Flight Sciences Composite aircraft : How to make Airplanes Out of Cloth Tim Nuhfer Aerostructures Design Aurora Flight Sciences 2 10/8/2014 How I got to where I am today Grew up in Florida Aerospace Engineering Lockheed Martin, Marietta, GA F-22 Raptor, Liaison Engineering Gulfstream Aerospace, Savannah, GA Material Review Board and Composites Shop Northrop Grumman, Melbourne, FL Vehicle Structures / Crew and Equipment Images from Lockheed Martin, Gulfstream Aerospace, Northrop Grumman Aurora Flight Sciences 3 10/8/2014 In-house UAV products Orion Centaur Skate aircraft structures Sikorsky, Boeing, Northrop Grumman, Lockheed Martin, and others Yes, we compete and team together Internship opportunities, even to high schoolers!

2 Manassas, VA Cambridge MA Columbus, MS Bridgeport, WV Aurora Flight Sciences 4 10/8/2014 How do we design an airplane? Requirements Customer tells us what they would like an airplane to do Concept Design Small teams from several different companies comes up with designs that meet those requirements. One or more hopefully gets a contract. Preliminary Design A larger team brings a dose of reality to the concept. Aerodynamics, propulsion, computers, software, electrical, payload, structure, mechanical systems. Detailed Design Create drawings, tooling, manufacturing planning, lots of coding Build, Test, Assemble, Test, Integrate, Test, Fly, Test, Modifications and Upgrades, Aurora Flight Sciences 5 10/8/2014 What are Composites ?

3 Any structure made of multiple types of materials laminated to form Composite structure stronger than the basic materials Wood, the original Composite Aluminum sheets laminated with other sheets Carbon fiber, fiberglass, Kevlar, boron fiber Aurora Flight Sciences 6 10/8/2014 How does carbon compare to other materials? Material Tensile Strength Modulus of Elasticity Density Cost Aluminum 65-75 ksi 10 Msi lb/in3 Medium Steel 180-280 ksi 25-30 Msi lb/in3 Low Carbon Fiber 75-300 ksi 10-33 Msi lb/in3 High Images from Composite Airframe Structures , Michael Nui.

4 1992 Aurora Flight Sciences 7 10/8/2014 Carbon Fiber Basics Wet Lay-up Dry fabric is layed into a mold Epoxy resin is mixed then worked into the fabric either by hand or using pressure or vacuum assisted resin transfer techniques Typical working time with resin is about 1 to 2 hrs Pre-impregnated uni and fabrics (pre-preg) Epoxy is pressed into fabric and tape using high pressure rollers Material is sandwiched between layers of carrier film and put onto rolls Bagged and stored frozen until needed Thawed when ready to work, typical outlife is 7 to 25 days Images from and Aurora Flight Sciences 8 10/8/2014 Sandwiches, What makes a Composite sandwich panel better than a solid panel?

5 Think of it like a beam Load Applied Replace the middle with core. make the outer fibers work to their full capability Images from Composite Airframe Structures , Michael Nui, 1992 Aurora Flight Sciences 9 10/8/2014 Practical uses Skin panels Thin aluminum requires stiffening to prevent buckling Composite sandwich panels can achieve the same or better buckling strength for the same or less weight Wing spars Wing Ribs Images from Composite Airframe Structures , Michael Nui, 1992 Aurora Flight Sciences 10 10/8/2014 How to make a part Start with a mold or tool Female tools will have the part laid up inside of it Male tools will have the part laid up on the outside Variety of tool materials Aluminum, steel, MDF, foam Must size the tool for thermal growth Clean and seal the tool before beginning the lay-up.

6 Aurora Flight Sciences 11 10/8/2014 Lay-up Thaw carbon Cut carbon from the roll Perform lay-up Aurora Flight Sciences 12 10/8/2014 Bagging and cooking Perforated release film Breather Cloth Vacuum bag Cook in oven Resin will flow throughout the laminate and take a set Some systems require an autoclave Aurora Flight Sciences 13 10/8/2014 Oven vs Autoclave cure cycles Oven cure Entire cure cycle under vacuum pressure Max pressure limited to atmospheric pressure (1 atm) Autoclave cure Autoclave is a large pressure vessel Higher pressure allows for greater compaction Tooling may be more expensive to withstand higher pressure forces Images from and Aurora Flight Sciences 14 10/8/2014 De-mold and trim After cure is done Cut open bag Pull part from the mold Trim part to size Sand and de-burr Aurora Flight Sciences 15 10/8/2014 Parts are ready, let s build an airplane Parts are held together in assembly jigs and bonded or bolted together Image sources.

7 Lockheed Martin and Aurora Flight Sciences Aurora s Orion Wing Assembly Lockheed Martin s Advanced Composites Cargo aircraft Fuselage Assembly Aurora Flight Sciences 16 10/8/2014 What I use from school Math Algebra, Geometry, Trigonometry on a weekly or daily basis Calculus somewhat more rarely Knowing what the calculus means allows me to make simplifications English Need to be able to write reports and make presentations Chemistry / Materials science Understanding how materials interact with each other is critical Understanding crystal structure of metals and how it relates to stresses Physics F=Ma F=0 M=0 Knowing how to draw a freebody diagram Programming Basic understanding of programming logic is critical to being able to use

8 Most engineering software to its fullest Art The most brilliant ideas are useless if you can t present the idea clearly enough for someone else to make it Crafts With composites, being able to use a ruler to draw and cut a straight line is critical Aurora Flight Sciences 17 10/8/2014 Questions?