Discontinuities that will cause
stress risers & premature failures
|Hard Spots, smard schplots, you
say........ as I was just trimming my shrubbery, a perfect
example came to me: I was breaking dead branches so they would
fit into my trash bin. Little ones, I could easily break between
my hands. As they got bigger, I broke them over my knee. Perfect
example of a hard spot!!
Trying to break the stouter ones between
my hands caused the sticks to bend, but not break. The moment I
introduced the hard spot (my knee), I could break them easily,
because my knee caused a stress riser.
||Rail crack under the
forward heel of a sandwich kite board
||Marinetex field repair
Water begins to ooze out
||Outer fiberglass ground
Fracture visible in Carbon cloth that
emerges from beneath edge of veneer heel reinforcement
||Carbon cloth ground away.
Fracture visible in PVC sheet foam
||Fractured PVC sheet foam
ground away some more.
Fractures radiate from edge of veneer reinforcement.
This edge acted as a hinge, with the very rigid veneer patch digging into the
much more flexible PVC-based structure beneath it.
Placing such an edge near a major load (heel) is a
sure-fire way to cause premature failure.
more stress risers here
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