Originally Posted by
unterhausen
my point is that as long as the epoxy is of sufficient strength for structural stability, it doesn't affect the overall stiffness of the aggregate structure that much. I suppose it would take fea to really show that. I'm sure it can be seen in an analysis, particularly if the frame is extremely lightweight.
That was my point: if you replaced the resin in my example with something which was four times softer (0.9 GPa) the overall stiffness of the aggregate sructure changes from (0.6 x 300 + 0.4 x 3.5) = 181.4 to (0.6 x 300 + 0.4 x 0.9) = 180.4, a change of less than 0.6%.