Effects of Strand Length
Specific mean values and coefficients of
variation of mechanical properties tested in tension,
compression and bending are given in Table 2.
The coefficients of variation, although seeming
relatively high (0% - 35%), are in the same range
of solid wood reported at 14% - 34% (Wood
Handbook, 1999).
For tension parallel to grain, the OSL made
of longer strands exhibited higher sUTS. Statistical
analysis showed that the results are highly
significant (Pr < 0.01). However, for the perpendicular
to grain direction there was no obvious
effect of the strand length on the sUTS. This is
explained by the very weak cohesive force (of
wood itself) in this direction. As a result, the sUTS
parallel to grain is about 35 times higher than that
of perpendicular to grain. The sTMOE parallel to grain is about 6.5 times higher than that of the
other direction. There is no significant evidence of
the role of the strand length in either direction.
It was found that sUCS and sCMOE parallel
to grain increased as the strand length increased
(Pr < 0.05), but were statistically insignificant for
the perpendicular-to-grain direction. The sCMOE
parallel to grain was about 18 times of that perpendicular
to grain. The OSL with longer strand
was significantly stronger than the shorter one in