Get the best. Get Logideath : )
Posted on 06/26/2023 9:42:29 AM PDT by Chad C. Mulligan
My recollection was the port was useless at that depth and cameras would show the occupants of the wreck.
Just like Everest, it’s so they can say “they” did it. Even with the hundreds of folks who have summited, I can’t say I know or have met any of them. Space travel will be the next incident IMO.
That was the deformation in the viewport itself (which is a clear acrylic dome) according to the guy who did this analysis. He said that the CEO had said the dome had flexed inward by several inches.
I have been looking for papers concerning the fatigue failure characteristics and life of composite materials. It is scattered and conflicting. On the one hand, in aerospace, the materials are lauded for being light, ductile and strong but little discussion so far that is to the point about fatigue resistance. They deform elastically and plastically. Since the Windecker Eagle aircraft composites have been studied for aviation. Most of the applications are in some form of tension and bending moment with some torsion. Axial loads in bending are OK but torsional loads are sketchy leading to delamination and failure.
In the preliminary, for subsea application, I have found this paper. In the conclusion and preamble it says their finding are:
“The crack growth rates of the specimens tested in ambient [temperature] and high pressure seawater were found to be approximately ten times higher than the growth rates of the specimens tested in ambient air”
I have not read further to learn the reason. I suspect it is high pressure water intrusion tending to delaminate the fiber and eppoxy matrix leading to crack propagation and failure.
Hmmmmm?
https://www.iccm-central.org/Proceedings/ICCM11proceedings/papers/ICCM11_V1_22.pdf
In another interesting excerpt from the literature search I find this:
“damage process in composite materials consists of three stages which is as
shown in Figure 2.1. Stage 1 occurs during the first 10-15% of life where the damage rate
is very rapid. Stage 2 occurs during the next 70-80% of fatigue life during which the
damage continue to grow with time but at a slower rate than Stage 1. Stage 3 corresponds
to 10-15% where continued cyclic loading accelerates due to severe damage caused
during the Stage 2.”
pp4 of https://researchrepository.wvu.edu/cgi/viewcontent.cgi?article=5214&context=etd
The previously cited paper suggests that failure would be even more accelerated in high pressure water. I imagine the water seeping into cracks and hydraucally pushing the matrix apart leading to accelerated delamination.
On pp 1392 and Fig. 3 of; https://dr.lib.iastate.edu/server/api/core/bitstreams/91623021-4d48-427c-9ac4-88824914b612/content
“...specific compression fatigue for composites is shown. Note the plastic deformation as permanent strain is very fast, the structural stiffness falls pretty quickly at first then stabilizes, as previous citations suggest, then falls off rapidly.”
One other note I saw in the brief literature search and perusal, fatigue life depends on the rate of application of load in composites, more-so than in metals. Recall that the operating procedure for the submersible was to “free fall” to dive depth. That statement gave me the willies when I first read it. Just not done, not prudent for load applications. I would not recommend it for steel or anything.
The submersible in question only had the very few cycles but the early onset of nearly 20% reduction in strength would not be unexpected. However, I also suspect the plexiglass viewing port having been descried by the owner as, “deflecting several inches under load” was the original source of failure. Either that or the glue joint between the titanium ring and the composite tube. It also looks to me that just a literature search would have condemned the materials selected for the application in my opinion. Never mind that the viewing port was admittedly UNDERDESIGNED!!!
This is what happens when an electrical engineer gets into structural and materials science? There is a reason it is against the code of practice to stamp and seal outside your area of expertise.
Yes, isn’t that absurd?
More money than good sense.
With a good set of speakers I would rather listen to and view a concert from the comfort of my den. The vantage point is much better and the effort to go is none.
The older I get the more vicariously inclined I become. Remote sensing is the bees knees and I haven’t even yet tried VR goggles.
It would have me also.
Still, the guy was able to get these folks to buy in, and
that’s why I blame him.
I just started reading this, probably great analysis, but he starts off with the weight of the water as 62.4 lbs per cubic foot, not 64 lbs which is the weight of seawater.
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