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Regarding the failure of my carbon fiber whisker pole under benign conditions, 15 knots, no fouls:
I heard recently from a senior director of engineering at a well known aerospace company, who took an interest in the question. Here are his remarks (He doesn't want his company associated with his comments on composites)
"Typically, failing at one end or the other is usually a sign that the truss beam isn't getting to act like a truss beam. For a long skinny tube to resist compression, it has to be free of loading at either end, which leaves it in "pure compression" or "pure tension"...
"If in fact one end is clamped, then any out of plane motion at the far end will also produce bending in the beam, which will be highest at the clamped end:
"So it could be that your pole temporarily bound up at one end, and then any "jostling" at the other end would have produced failure in bending near the bound end.
"It's also very possible that the pole wasn't bound up at either end but just went into buckling, and failed wherever it failed. I've attached an Excel spreadsheet with an educated guess at your whisper pole using three materials- Al, steel, and CF laminate. (The CF laminate data by the way is from https://agate.niar.wichita.edu/ which will tell you more than you will ever want to know about the behavior of any composite- make sure to look at "laminate" properties since that's what you'd find in actual products.) Note that this is an idealized model of a pure continuous tube, not a nested set of tubes.
"Looking at your video it seems pretty clear to me that the CF laminate pole was under a serious axial load and then took a good jolt in the off-axis direction that turned your straight pole into a bow:
"...and the bow of course has much less ability to resist the continuous compression load, which made it bow more, which made it weaker, etc, etc, etc. A few hundred milliseconds later, disaster. That low Euler margin would mean the pole was ready to buckle if it had either a sufficient jolt or any manufacturing errors of any kind."
Materials comparison:
Regarding the failure of my carbon fiber whisker pole under benign conditions, 15 knots, no fouls:
I heard recently from a senior director of engineering at a well known aerospace company, who took an interest in the question. Here are his remarks (He doesn't want his company associated with his comments on composites)
"Typically, failing at one end or the other is usually a sign that the truss beam isn't getting to act like a truss beam. For a long skinny tube to resist compression, it has to be free of loading at either end, which leaves it in "pure compression" or "pure tension"...
"If in fact one end is clamped, then any out of plane motion at the far end will also produce bending in the beam, which will be highest at the clamped end:
"So it could be that your pole temporarily bound up at one end, and then any "jostling" at the other end would have produced failure in bending near the bound end.
"It's also very possible that the pole wasn't bound up at either end but just went into buckling, and failed wherever it failed. I've attached an Excel spreadsheet with an educated guess at your whisper pole using three materials- Al, steel, and CF laminate. (The CF laminate data by the way is from https://agate.niar.wichita.edu/ which will tell you more than you will ever want to know about the behavior of any composite- make sure to look at "laminate" properties since that's what you'd find in actual products.) Note that this is an idealized model of a pure continuous tube, not a nested set of tubes.
"Looking at your video it seems pretty clear to me that the CF laminate pole was under a serious axial load and then took a good jolt in the off-axis direction that turned your straight pole into a bow:
"...and the bow of course has much less ability to resist the continuous compression load, which made it bow more, which made it weaker, etc, etc, etc. A few hundred milliseconds later, disaster. That low Euler margin would mean the pole was ready to buckle if it had either a sufficient jolt or any manufacturing errors of any kind."
Materials comparison:
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