We discuss the effect of fibre strength and diameter on the balance of mech
anical properties of glass-reinforced polyamide 6,6. The results show that
the elastic properties of injection-moulded short-glass-fibre-reinforced po
lyamide 6,6 are not strongly influenced by fibre diameter in the 10-17 micr
on range. The ultimate properties of these composites (strength and Izod im
pact behaviour) showed a clear dependence on fibre diameter and were increa
sed by the presence of high-strength S-2 glass fibres. The relationship bet
ween the observed mechanical properties and the length, diameter and orient
ation of the fibres is explored. We have measured fibre length as a functio
n of diameter in composites containing a single glass-reinforcement product
and blends of two glass products. The reduction in glass-fibre length from
glass-fibre production to final composite moulding has been followed step
by step. The final composite mechanical properties, the fibre length, stren
gth, diameter and orientation are all inter-related. (C) 1999 Elsevier Scie
nce Ltd. All rights reserved.