3 Point Bend Tests

Last updated 07/09/2008

Carbon Fiber / Nomex Honeycomb Comparison Test

This test was set up to contrast the strength of a carbon fiber covered Nomex honey comb material from ACP Composites. The test was performed using 1.5" x 5" samples in my small 3-point bend fixture. The test is the same as below, but the span (the distance between the rollers) is 3", vs the 2" in the test below.

The data shows that the laminate material is not as strong as the aircraft plywood in 3-point bending. You will notice that it continued to bend rather than snap, or break. This is evidenced buy looking at the graphs and also suggests that the laminate material is "tough". Another factor in choosing this material is the obvious weight reduction. I hope to receive more CF/Honeycomb samples in the future.

Giant Leap Honeycomb Comparison Test

This test is of three each, 1/8" and 1/4" thick by 1.5" x 5" Giant Leap Honeycomb fin material. The samples were the same dimensions tested in the "Carbon Fiber / Nomex Honeycomb Comparison Test" above with the same span being 3.0". Remarkably, the 1/8" samples weighed virtually the same as the 1/4" samples. Samples provided by Brianc.

Fin Material 3 Point Bend Test

These are strips of fin materials provided by Greg Deputy. There were three groups of three materials. The three materials were 1/8" balsa wood, 4 ply 3/16 plywood, and 1/8" G10. Each of these were divided into three groups: Bare, fiberglassed, and carbon fiber laminate. As a comparison, the remaining samples of John Coker's materials were also tested. The distance between the two lower rollers or "span" was 2.00". Strain rate was 0.500 in/min. Click here to see the bend test before the break and here for after the break.

The largest standard deviation was with the laminated balsa. This was due to delaminating of the overlay. The tests with the lower results delaminated sooner during the test than did the tests with the higher results.

Robert DeHate's Fin Material Test

The test samples were 3" x 5". They were made from 1/4" aircraft plywood. Three baseline samples were tested with no modifications. The three other samples were tested had a 1" x 3" section cut out of the middle. The section removed was then filled with expanding foam. The entire surfaces were then laminated with carbon fiber cloth. The test was conducted on a three-point bend fixture. The span, or distance between the two lower rollers, was 4.5"