Page 87 - Plastics Engineering

70 Mechanical Behaviour of Plastics

per unit length of 140 g/m (equivalent to a solid thickness of 10 mm). If a
different solid thickness is of interest then the optimum skin thickness would
need to be scaled accordingly. For example, for a 5 mm thick solid beam which
is to be converted to a foam sandwich beam of the same weight per unit length,
the optimum skin thickness would be half of the value shown in Fig. 2.20. The
optimum skidcore thickness ratios are shown in Fig. 2.21.

1.66
1.64
E
Z; 1.6

5 d 1.58
1.56
f 1.54
E
1.52
1.5

1.48
1.46
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7’ 0.8 0.9
Densny ratk (core:-)

Fig. 2.20 Variation of optimum skin thich with core: skin density ratio

90
80
70
60
50

40
:: ;
30

0
0 0.1 0.2 0.3 0.4 0.5 0.6
Density ratlo (core:skln)

Fig. 2.21 Optimum skin to core ratio for constant weight