So , Nick Zatezalo mentioned this one , from eBay , with the comment :
"Steel is real & repairable.
Plastic is plastic & toast."
I got around to looking at this auction ( ended by the way , so it's purely educational now ) .
Wow , interesting . I don't have any big issues with fiber-reinforced-plastic . I'm not on any crusade . But this is kinda thought provoking .
A $ 4,000.00 dollar plastic bicycle , sold for $700 .
You can reinforce your plastic "matrix" with all kinds of fibers :
glass ( even S glass , E glass , etc ) ,
carbon ( "graphite" ) ,
Kevlar ( Aramid ) ,
Spectra ( anybody remember "Nick Fury agent of S.H.I.E.L.D." ? )
boron
wood ( "cold molded" mahogany is some beautiful stuff )
But , beside the cheerful problem called "catastrophic failure" , exhibited by fiber reinforced plastics , here's another little factor - galvanic failure .
Anyone who has ever dealt with steel and aluminum in close contact , for long periods of time , understands that SOMETHING happens between those two metals . Take a steel ( iron ) alloy bicycle frame , insert an aluminum ( aluminium ) alloy seat post and stem , neglect to include the proper amount of grease , drip some salty sweat on it for a few months , then just TRY to pull the aluminum alloy away from the steel alloy . . .
That's an electrical situation . Galvanic reactions . Fun stuff .
Yeah , so , I've read in some aviation magazines about carbon fiber reinforced plastic .
You really should be careful about direct contact between the little fibers themselves , and all the metal parts .
Remember those "dry cells" in your flashlight ? Those are the ones that are usually mis-named "batteries" ( they are cells , not batteries , look it up ) . You do remember that the main ingredient in plain old ordinary dry cells is . . . carbon ?
So , you take your large sheets , or tubes , of carbon fiber reinforced plastic , and you drill some holes . That exposes the ends of the carbon fibers . Now you stick some pieces of aluminum into some of the holes , and some steel ( iron ) fasteners in direct contact along with the aluminum . Finally , you include a little water ( humidity will work ) , and a little salt ( sea coast humidity is fine , human sweat is great too , but riding on roads which have been salted is another good one ) .
Congratulations !
You're a new parent , you've got electricity !
Congratulations , it's a dry cell !
And if those little tiny carbon fibers start to exchange something ( electrons , ions , whatever ) with the metal bits , they may easily start to swell , or even shrink . That plastic matrix can only handle so much internal stress of that kind . Something has got to give way .
Oh! And P.S. - you don't really even need to drill any holes . There are usually plenty of aluminum sleeve inserts , bonded into the frame during manufacture . So , were they careful enough about preventing carbon to aluminum contact , at every one of those places ? Or did they get just a little sloppy ? Hey , as long as you ride where it's always 0% humidity , it won't be a problem . Just don't sweat .
Oh , and never forget that plastics are sensitive to U.V. light , "photo-degrade-able" .
And in the end , iron oxidizes ( "rust" ) , aluminum oxidizes ( "corrosion" ) , and plastic dies too .
Raoul Delmare
Marysville Kansas