Page 38 - Plastics Engineering

General Properties of Plastics 21

50

High-heat grade
40
Medium-impact
Hig h-impact
-impact

Strain (%)
Fig. 1.5 Effect of grade on mechanical properties of ABS

Slope represents tangent,
OrYoung‘s modulus ‘4/ /k sm

0 c’
Strain

Fig. 1.6 Tangent and secant modulus

control purposes, not for design. Since the tangent modulus at the origin is
sometimes difficult to determine precisely, a secant modulus is often quoted to
remove any ambiguity. A selected strain value of, say 2% (point C’, Fig. 1.6)
enables a precise point, C, on the stress-strain curve to be identified. The slope
of a line through C and 0 is the secant modulus. npical short-term mechanical