Carbon-fiber composite structure is tricky to analyze (“Oceangate Sub’s design may have destined it for disaster,” The Herald, June 23). Carbon fibers are 10-times stronger than aluminum alloy, but the glue, or epoxy, that holds them together is 10-times weaker.
The submersible designers likely know this and built very detailed computer models to verify that the stresses in the various directions didn’t exceed the carbon and epoxy limits. However, such models are complex and could easily miss an area which could cause delamination and subsequent failure. Also, the manufacturing difficulties in laying up 5-inch thick walls of carbon-epoxy tape to ensure absolute integrity without delamination are many.
Such problems are the reason why aircraft manufacturers have only recently dared to make aircraft out of the material. It’s been around for 50 years but only in the last decade or so have people developed the analytical and manufacturing tools to use it.
Len St. Clare
Mukilteo
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