Aluminum silicon carbide brake calipers

Example of a sufficiently narrow presentation topic, and substantive failure mode (brake fade from aluminum creep under high temperature).

When you're doing a presentation, you don't have to explain everything. That's what questions and answers are for. You're just trying to introduce the topic. So don't tell me about use of composites in automobiles — that's a little broad. If you want to say use of aluminum-silicon-carbide calipers for lightweight disc brakes, great, that's specific enough, and you can get down to why they do it or why they don't do it.

Mid-80s automotive industry attempt to replace cast iron brake calipers with Al-SiC metal matrix composite. Star Wars era. Failed initially because aluminum creeps and the calipers sprung open after two or three hard brake applications — brake fade. Tom has heard the problem has since been solved.

Sprung weight is more important in automobiles. Here we have a disk brake and a drum brake. At one time, back in the mid-80s, some people had developed a technique to cast aluminum silicon carbide metal matrix composites. Reagan had started Star Wars, and people thought, oh this is inexpensive, we've lowered the cost of this composite material. Several of the automotive companies tried it — they made the caliper assembly with the little hydraulic pistons that squeeze against the disk pad. They wanted to make this out of aluminum silicon carbide metal matrix composite. It's cast iron right now. It's heavy, it's on the axle which is bouncing up and down. If you can reduce the weight on the axle, you'll get better maneuverability and handling. Anybody know what the automotive companies call the whole general area of handling and noise and stuff? NVH. Noise, vibration, and harshness. The sprung part, what's on the axle, is a large contributor to NVH. If you're going to buy a Cadillac that's nice and quiet running, you want to have less mass on the axles.