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Mechanical Behaviour of Plastics 81

3

2.5

2

1.5

1

0.5

0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
hlD
Fig. 2.29 Design of ribbed beams

2.10 Stiffening Mechanisms in Other Moulding Situations
In some moulding methods such as blow moulding, thermoforming and rota-
tional moulding, it is difficult if not impossible to produce stiffening ribs. Hence
other stiffening configurations such as corrugations have to be used. Fig. 2.30
illustrates a typical repeat unit in such a corrugation. The second moment of

Fig. 2.30 Cormgation profile