Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 1 Lecture 5 & 6 Carbon Fiber in Automakers The Ferrri Enzo, of which only 399 will be built, has a monocque carbon fiber chasses and carbon fiber body panel With the exception of its roof and doors, Lamborghini Murcielago’s exterior body panel are modeled from Cytec prepreg and autoclave cured Its engine mounted on carbon fiber to reduce vibration, the 603 hp, all-carbon Porche Carrera GT hit the street 2003 Reading due next week Mid-term is next week

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 2 Carbon Fiber in Automakers The TVR Tuscan R, exterior bodywork of fiber MG Rover 36 carbon fiber components Corvette exterior and hood light weight carbon fiber

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 3 Constituent Materials 2. Boron Filament Reinforced Fiber  High strength but and very high modulus: 60 Msi (5 times the glass)  High specific moduli (ρ =2.6 g/cc)  Posses E required for critical parts such as wing skins, etc.  Process can performed continuously without degrading fiber properties.  High performance could be fabricated with an appropriate matrix resin such as epoxy. In late 60’s T-39 center wing box, F-100 wing cover, F-111B wing tip fabricated from Boron/epoxy.

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 4 Boron Filament Reinforced Fiber Boron filaments are produced by the CVD of B on a tungsten (W) substrate as shown: Boron filaments are produced in a reactor: 1- Stage 1: W is heated (2200 F) in presence of H2 2- resistively heated (2400 F) in a mixture of H2 and BCL3 with elemental B being deposited on the W substrate. - overall reactor length is 3 meter. - Plate at rate of 0.1 mils in dia per second. - Production rate is 2 lb.wk - Employ several sectors simultaneously to match requirement

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 5 Boron Filament Reinforced Fiber  Three different diameters 4.0, 5.6, and 8.0 mils.  Filaments are very expensive ($200/lb) due to cost of BCL3 ($40/lb) and W ($50/lb) of filament.  Also is very energy intensive process.  Surface has been described as a corn cob type morphology:  the kernel morphology is believed to be responsible for properties such as: -high transverse tension - high flat-wise tension  Self adhesive, no need for bonding.

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 6 Boron Filament Reinforced Fiber Properties of B filaments PropertiesValue ρ (g/cc)2.65 σT (10^3 psi)500 ET (10^6)56.0 ε (%)0.9 -Resist moisture and corrosives -Possess excellent elevated temperature properties Properties of Unidirectional B/Ep composites. Properties0°90° σT (Ksi)27013 ET (Msi)303 σc (Ksi) ET (Msi)303 Coeff. Of Thermal Expansion C-T-E (10^-6 in/in/F) -high E, and high compression strength prop. Hybrid: two or more fibers symmetry is required

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 7 Boron Filament Applications Applications B/EP have high stiffness and compression properties, used in: -aircraft : wings, stabilizers, etc. -Leisure: Tennis racquets, golf clubs. - also combined with other materials such as gr/ep to get hybrid to take advantage of B properties. -Also used to boost composites strength.

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 8 3- Carbon/Graphite Fibers -high σ, high E light weight which predominant reinforcement in ad.composites. -Higher specific properties than B -Offering significant cost and handling advantages over B -Very attractive to use in high performance applications such as primary aircraft structures. -Relatively low cost gets it into commercial sector. -Thomas Edison’s first used carbon fiber produced by cellulose fibers. -Heat treated at 1650 F -Carburizing at 4500 F σT= Ksi -E= 6 Msi -T> 4500 F increase modulus.

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 9 Carbon Fiber Preparation Carbon fibers are prepared from either -organic fiber precursors (to come) -Pitch PAN (Important) Step 1: PAN preparation: Intermolecular bonding due to polar nitrate groups. Produced by wet spinning process in which have: 1- solution of polymer in suitable solvent, 2- is spun into coagulating bath 3- washed 4- stretched, 5- dried. Step 2: Stabilization Against polymer relaxation, or softening (which caose loss of orientation)

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 10 Carbon Fiber Preparation Step 3: Carbonization The stabilized PAN fibers are pyrolyzed into C fiber. High mechanical properties C fibers are developed Process is carried out in inert atmosphere at C Step 4: Graphitization: High temperature step: - on order of C - improves tensile modulus of fibers. Graphite vs. C fiber Graphite fiber- carbon content > 99 % C fiber = 80-95% Density: C: 1.7 g/cc, Gr: 2.1 g/cc PAN fiber diameter decreased by factor of 2 after final process

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 11 PAN Summary. Pitch: the process of making graphite fiber from a pitch precursor typically involves the following steps: 1- Conversion of pitch to a mesophase pitch (liquid crystal) 2- Spinning mesophase pitch into fibers 3- Stabilization 4- Carbonization 5- Graphitization

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 12 Melt Spinning a Mesophase pitch- based Carbon Fiber

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 13 Pitch-based Carbon Fiber Process

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 14 Summary

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 15 Fiber and Reinforcement Properties

Mechanical Engineering Department Advanced Composites Dr. Talal Mandourah 16 Fiber and Reinforcement Properties Graphite fibers are available in the following forms: -continuous -Chopped -Woven fabrics -Braids -Mats Continuous fibers are available as yarns and tows Tow: bundle for numerous micron-size filament A variety of tow size are available: 1000, 2000, 3000, 6000, 12K The most common form is the prepreg tape: prepared by tows to form tape width and thickness: 10,000. Typical tape width: 1, 3, 6, 12, 48, 60 inches