Destructive testing

Categories: Materials

Took a few minutes to perform some destructive testing on the first bulkhead that was infused. Wanted to make sure the bond between the glass and foam was good and also nervous about a boat built of nothing but foam and fiberglass.. 🙂

First test I have no pictures of – it involved a strip of laminate about 7″ long and maybe 1″ wide at best. Braced it between two low shelves and put some weight on it with my foot. Was surprised that it actually took what felt like around 80 lbs before snapping. Failure occured on top skin, core snapped and the bottom skin was still somewhat intact.

Next test involved a slightly bigger piece, same “test”. I stood with my foot on the piece and a hand pressing down on the shelf to support my weight. Piece bent significantly but did not actually start snapping and break until I started lifting on my hand to transfer the remainder of the weight to the piece. I’d say I had a good 170-180 lbs on that thin part when it broke.

Last test was just to see what would happen with the bigger piece (center of bulkhead that is cut away for access). Was too small to try standing on, so we put it on the vice and used a large C-Clamp.


Another strip of laminate was placed on top to help distribute the pressure. At this stage you’ll notice the top strip is compressed but the test piece is only just starting to bend. I will also note that the 5lbs density foam doesn’t like being crushed. Will make absolute sure anything getting bolted thru has 12lbs foam on it!


Now you’ll notice the test piece becoming quite deformed. At this point, none of the fibers have begun to crack yet. I am QUITE surprised at the strength of this laminate, having never worked with a foam sandwich before.


Last two pictures, the laminate finally fails. First there is some popping of the fibers, then with a little more pressure it finally fails. I didn’t get a good picture, but the failure occurred at some jig-saw cuts where from when I cut it out of the bulkhead – that side was not braced completely on the vice (second picture). There is a chance it would have taken even more stress if it was placed a little better.


No – it wasn’t very scientific – no real measurements could be made regarding how much stress was applied. This was more or less a “we’ve broken other stuff this way before, how much will this foam stuff take?”….

We are both believers now.