At 03:41 PM 3/26/2009, Roland wrote:
>My favorite these days is JB Weld - some kind of super strong glue.  Tired
>various epoxies, but JB Weld seems to be the strongest.  Local Home Depot or

JB Weld, MarineTex, PC-7 are examples of filled epoxies, i.e. they
contain particles of aluminum or other substances mixed in with the
resin.  This makes them tough and resilient and good at space-filling
repairs, because they retain their tensile strength across gaps.

Unfilled epoxies on the other hand are fluid and easy to work, but
they are only strong in tension in very thin layers because they are
brittle.  They are excellent for repairing closely fitted breaks that
have reasonable amounts of surface area and a rough surface (broken
china plate is a good example partly because of its concave shape; a
flat disk of the same dimensions would probably result in a weak
repair), and as a matrix for composite repairs using glass fiber or
other materials that are strong in tension.  They will not wick into
cracks, but if the edges of the crack can be flexed apart several
times they can be pulled in by suction.

Tensile strength of epoxies under good conditions can be around 4,000
psi; a composite with glass fiber may reach 40,000 psi or better in
tension and has good impact properties.  40,000 psi is similar to
mild steel.  Individual glass fibers are actually much stronger than steel.

  --
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'89 Po' White Star "Scamp"