David Billington wrote:
Christopher Tidy wrote:

Jon Danniken wrote:

"Carl" wrote:

I google'd "grade 8 bolts brittle", and found this article that seems
pretty informative. The author is a Senior Staff Mechanical Engineer
for Lockheed Martin (DAMHIKT)

http://www.rockcrawler.com/techrepor...ners/index.asp

Go with the grade 8.



Great article, thanks Carl!


That article is quite right that brittleness is relative, and that
materials are only usually thought of as brittle when they fracture
before reaching their elastic limit. Even the most brittle steel isn't
as brittle as glass.

Best wishes,

Chris

Then I seem to remember that for glass the brittleness only comes into
effect when the thickness of the piece exceeds the critical crack length
of the material, hence the reason that glass fibre exhibits the
properties it does, its diameter is less than the critical crack length.

Not sure about this. Won't the critical crack length depend on the
stress the material is under?

The fibres in glass fibre are very flexible because they're very thin,
but I've never actually tried to break a single fibre. I'll have to try
it sometime.

Also, when a crack begins to grow in a composite made of glass fibre and
resin, it will turn and travel sideways along the boundary between the
resin and the fibre. This increases the fracture toughness.

Best wishes,

Chris