Page 244 - Plastics Engineering
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Mechanical Behaviour of Composites 227
'7 Stresses
1
+
34
(a)
dia = d
1
+,It -4 It
T4 34
(c)
Fig. 3.29 Short Fibre Composites
The stress distribution in short fibres is often simplified to the form shown
in Fig. 3.29(c)
It is evident from Fig. 3.29 that there is a minimum fibre length which will
permit the fibre to achieve its full load-carrying potential. The minimum fibR
length in which the maximum fibre stress, (of)-, can be achieved is called
the load transfer length, e,. The value of may be determined from a simple
force balance
force transmitted by shear at interface = ty(l/2)nd
force exerted by fibre = 0f(nd2/4)
hence,
(3.43)
where, t,, is the shear strength of the fibrdmatrix interface.
The maximum value of e, will occur when (of),, reaches the tensile
strength of the fibre, ofu, and this is defined as the critical fibre length, e,
(3.44)
