Page 56 - Plastics Engineering

General Properties of Plastics 39

Table 1.1 1
Desirability factors for some common loading configurations
Desirability factor, Df
Component Strength basis Stiffness basis

Rectangular beam with fixed width a;/=/pc E113/pC
Struts or ties UYIPC EIPC
-
Thin wall cylinders under pressure aYlPC
Thin wall shafts in tension rmlPC GIPC
Long rods in compression (buckling) - E112/pC

Table 1.12
Desirability factors for a range of materials

Proof or
E
fracture - - E112 ~113
--
*Y
Density, p stress n Modulus P P P P
Material kg/m3 (MN/m 2' E (GN/m2) (x10-3) (x10-3) (xIo-~)
)
Aluminium (pure) 2700 90 70 0.033 0.026 3.51 3.12 1.53
Aluminium alloy 2810 500 71 0.178 0.025 7.95 3.0 I .47
Stainless steel 7855 980 I85 0.125 0.024 4.0 1.73 0.73
Titanium alloy 4420 900 107 0.204 0.024 6.78 2.34 1.07
Spruce 450 35 9 0.078 0.020 13.15 6.67 4.62
GRP (80%
unidirectional
glass in
polyester) 2000 1240 48 0.62 0.024 17.6 3.46 1.82
CFRP (60%
unidirectional
fibres in
epoxy) 1500 1050 189 0.7 0.126 21.6 9.16 3.82
Nylon 66 1140 70 0.78* 0.061 6.8 x 8.34 0.77 0.81
ABS Io40 35 1.2* 0.034 1 I .5 5.68 1.05 1.02
Polycarbonate 1 I50 60 2.0* 0.052 17.4 x 6.73 1.23 1.09
PEEK (+ 30% C) 1450 215 15.5 0.19 0.01 1 10.1 2.7 I .72
* 1500 h creep modules

Tables 1.11 and 1.12 give desirability factors for configurations other than
the beam analysed above and typical numerical values of these factors for a
range of materials.

Bibliography
Waterman, N.A. The Selection and Use of Engineering Materials, Design Council, London (1979)
Crane, F.A.C. and Charles, J.A. Selection and Use of Engineering Materials Buttenvorths,
London ( 1984)