sci.polymers or sci.materials might be a better bet. There are two general ways you can make a given epoxy harder: bake it (an hour at 100C does wonders) or put filler in it.
If you're bonding hard materials, you might want to use a glass bead filler. When you squeeze the bondline down, the spheres contact the surface, and as the epoxy shrinks (1% or so), it applies a preload to the glass/substrate interfaces. That's a pretty stiff joint.
If you're trying to do something in shear, e.g. attach a strain gauge, glue is not your friend at all. You might be better off using solder or indium bonding or something like that.
Cheers,
Phil Hobbs