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To: ahhaha who wrote (80229)	12/26/2001 10:49:34 AM
From: long-gone	Read Replies (1) \| Respond to of 116922

You do know there were those that said the greater use of glass & metals would eliminate (or very nearly) the use of wood & masonry. They were as just as wrong as those who predicted we'd all own flying cars by the year 2000, by the year 2010 we'd have earthlings living full time in other solar systems, that by 1990 we'd have world peace, or by 1995 the world's population would have starved its self to death and mankind would cease to exist.

To: ahhaha who wrote (80229)	12/26/2001 1:51:49 PM
From: E. Charters	Read Replies (1) \| Respond to of 116922

You forget one thing. Cost. It is cheaper to mine a material than build it or scrap it often. This equation has been played out for decades with the mined, deoxidized iron pellet against scrap steel. Sometimes scrap won, sometimes they would fire up the pellet roasters. Cost is all. How much to make that fibre beam, and what is its lifespan? Fibre beams break a bit with each flexure. That is why you trash a pair of fibreglass skiis within 5 years - they lose all their spring. The base material is usually brittle for stiffness. Actually glass is not brittle, it just has no integrity when it has been surface-scratched. It cannot reweld dislocations like martensite. Your base material has to be stiff, not flexible as the fibre adds little stiffness, just the stopping of crack propagation. We will see more scrap from time to time, and from time to time more metal mining. Iron is a stable scrap-to-mining-ratio built over decades and adapted to the corrosion and fatigue cycle. We could build bridges massively of concrete and they would never fall down. We choose to replace. That is in the plan. 100 years from now we will want a different, larger bridge. Things are built to be replaced. The scrap becomes damn cheap. Hard for expensive, labour intensive composites to compete. We may see more titanium as the price to manufacture drops to a few scores of cents a pound with the new reverse electrolytics. Its long lifetime will be attractive in buildings that we don't anticipate wanting to scrap in less than 200 years. 500 years ago they built to last as labour to build was expensive. European cities have roads and bridges and buildings 500 and 2000 years old. It turns out to be no more efficient than today's replaceable mode, as the usage becomes congested and they are expensive to replace. I see one area of new material development. That is in relatively short life, low vibration, low load, fibre crete beams for spanning area. If the crack propagation problem with crete can be solved, then you have a long life beam under vibration. But solve the crack propagation and you don't need the fibre. Perhaps a combination of prestress and composite may be used for critical usages. But it has to be cheaper than rolled steel from scrap. EC<:-}