Today's KNOWLEDGE Share:The reason for Shrinkage

Today's KNOWLEDGE Share

The oriented skin will shrink only 0.1 or 0.2 %, where the transverse core will want to shrink possibly 1%.

The conflict results in a compressive stress in the skin, due to the action of the core, trying to shrink so much more than the skin. Easy, right ?

So the skin is in a fairly safe state of COMPRESSION (failure comes with tension).

Sure ?

Zooming inside the skin, we must realize that the very reason for the shrinkage to be so small in the fiber direction, is because the much higher shrinkage of the polymer is constrained by the glass fibers. So the polymer in between the fibers is desperately trying to shrink 2%, but the glass will keep the polymer under....TENSION !

So the skin is in compression yes, but the polymer, in the skin, is in tension !

source:Vito leo