Is old wood really "weaker" ??? Brittle vs weak

[Richard Brekne]

Of intererest from the book The Conservation of Wood Artifacts by Achim 
Unger  from page 37 comparing recent wood with aged wood.  You'll notice 
down at the bottom of page 37 a direct reference to a type of 
brittleness that is not really related to bending strength... rather 
impact strength.  You'll also notice that the stiffness of wood is a bit 
more complicated then what we usually talk about... 9 different and 
independant elastic constants are used.

Brittleness can be associated with the term weakness... but the words 
are not interchangeable.  An old piece of wood can easily be brittle in 
the sense that it will snap in two when its elastic limit is reached 
rather then bend... but it will take just as much force to reach this 
limit as in non brittle wood.

Cheers
RicB


http://books.google.com/books?id=M5vCl0jlCCUC&pg=PA37&lpg=PA37&dq=brittle+wood+strength&source=web&ots=G9bn8K9XMo&sig=2jzbJivS0WkxZrulXyy5w1ELC8w#PPA40,M1