Fired engineer calls 787's plastic fuselage unsafe
Join Date: Dec 2004
Location: swindon
Age: 44
Posts: 87
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Blip,
I agree with you that energy cannot be absorbed without distortion of the structure.
Race cars absorb energy based on known failure rate of the structure. The structure is based on layers of composite that “commit suicide” and disintegrate to manage the force of impact.
What I’m confused about is the assumption that the composite failure strength is less than that of “absolute Failure” of Aluminium (after buckling and distortion). In my (limited) experience on GA types I was always taught to make sure the composite failure rate was equal or greater than that of the “Absolute failure” of traditional material.
I have tried to demonstrate this in the following diagram.
Impact 1 – Composite structure Integrity remains intact; Aluminium Structure is deformed but some strength remains.
Impact 2 – Both Composite and Aluminium structure fail – no integral strength remains.
So are we to assume the Boeing intends for the Composite structure failure to be LESS that the absolute failure of alternatives?
Smala01
I agree with you that energy cannot be absorbed without distortion of the structure.
Race cars absorb energy based on known failure rate of the structure. The structure is based on layers of composite that “commit suicide” and disintegrate to manage the force of impact.
What I’m confused about is the assumption that the composite failure strength is less than that of “absolute Failure” of Aluminium (after buckling and distortion). In my (limited) experience on GA types I was always taught to make sure the composite failure rate was equal or greater than that of the “Absolute failure” of traditional material.
I have tried to demonstrate this in the following diagram.
Impact 1 – Composite structure Integrity remains intact; Aluminium Structure is deformed but some strength remains.
Impact 2 – Both Composite and Aluminium structure fail – no integral strength remains.
So are we to assume the Boeing intends for the Composite structure failure to be LESS that the absolute failure of alternatives?
Smala01
