Tensile properties
Typical stress-strain curves of specimens
tested in tension parallel and perpendicular to
grain are shown in Figure 1. The ultimate tensile
stress is the maximum stress appearing on the
stress-strain curve and the modulus of elasticity is the slope of the secant drawn from the original to
the maximum stress (ASTM E111, 1978). For the
parallel-to-grain test, it was found that the OSL
failed like brittle materials. The maximum stress
and strain tested in the direction parallel to grain
was substantially higher than that of perpendicular
to grain. The OSL is relatively weak in the direction
perpendicular to the grain. In some cases, a slip
occurred (as appears in Figure 1b) before the selftightening
grips firmly hold the specimens. This
did not have an effect on the mechanical property
evaluation since the modulus was determined from
the slope after the slip.