Comments by "Les" (@les8489) on "OceanGate Titan Hull - Hundreds of Ill-advised Carbon Fiber Grind Spots" video.

  1. This is the 3rd video from you I watched. I am speechless... Yes, you can do some machining of the bumps on the laminate - but not on a structure which works in compression and may be buckling critical. In cases where machining of the cured laminate is performed - this is only done on the sacrificial plies (not structural ones) and is properly accounted for in the analysis. Removal of up to 12 plies is something "innovative" indeed... This starts being a comedy (despite the tragic end of all people who took the last ride inside the Titan...) EDIT 1: LOL...12:10 The guy who was Director of Engineering admits having no background in mechanical or material engineering. Well...I am sure that art degrees fill the gap nicely, and that had a very good DEI program. Didn't they know that each carbon ply has a nominal thickness BEFORE CURE, which is somewhat larger than the CURED thickness (the cured thickness was measured on EVERY program I was involved in during my 40+ years of engineering practice)?! This has little impact on a 2D panel (which may have curvature or not), but on a circular structure (even after proper debulking) any reduction in thickness during cure will result in bumps. Interrupting the continuity of fibers by grinding transfers the load to the adjacent plies - in effect, a large stress concentration and a reduction in buckling strength. Grinding produces visual improvement - but the plies underneath still have a large degree of waviness...this is getting better and better... EDIT2: In my comments to another video I mentioned that laminates with no +/-45 plies are a definite NO-NO -precisely for the reasons mentioned above. The BOEING guy said that clearly enough - the design manuals at BOEING specify clearly what is the minimum percentage of cross-plies for the laminate to be acceptable in design. EDIT 3: 17:40 and onwards...very simplified explanation - but spot on in principle. And the funny thing is - to a large extent it could be analyzed. Analysis of damage tolerance, effects of play waviness/discontinuity of plies is nothing new and is routinely done when the designer and the analyst know what they should be doing (and when the accountants agree to the additional expense - which rarely happens). Not always easy, but doable - at least to the extent of pinpointing potential troubles. But no testing, no analysis of the ACTUAL shell (with defects) and hey-ho, hey-ho, into the depths we go...R.I.P.
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