[PSUBS-MAILIST] fiberglass as hull material

[Clifford Redus via Personal_Submersibles]

I concur 100% with Sean on this.  Even as a practicing mechanical engineer, it would take me weeks to do a stress analysis on the hull.  The only safe way to determine the strength of the hull is a destructive test where you take it failure.  After you complete the test, you lay up a second hull.  If you lay up the mat in a different orientation, the strength of the hull would be different.  This is why most builders use steel that has a very predictable and linear stress strain relationship.

Cliff

Sent from my iPad

> On Nov 21, 2014, at 4:37 PM, Sean T. Stevrnson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Fiber reinforced resin matrix composites cannot be modeled the same way as isotropic materials, owing to the strongly directional behaviour compared to the axes of curvature in pressure hull forms. The composites also introduce new modes of failure, such as interlayer delamination. That said, they can and have been used as pressure hull materials, but you generally will need to custom model the behavior with regard to your hull geometry. In a typical composite layup, the average material properties are approximately equal to the average material properties of the matrix and reinforcement in proportion to their respective volume fractions, but failure modes are still dictated by the weaker or more brittle material. Performance is also dependent on layer thickness and principal fiber orientation in each layer. Fiber reinforced composites will tend to fail catastrophically in a shear mode, versus yielding inelastically as with steel, so you! need to be very confident in your strength analysis to go this route. Unless you have a strong background in engineering, it may be more trouble than it's worth for a homebuilder.
> 
> Sean
> 
> 
>> On November 21, 2014 9:24:08 AM MST, roberto alvarez via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>> Hi did some one have information regarding the use of fiberglass cloth as hull material,  want replace the info on the calc 
>> 
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