EFFECTS OF THE DISTRIBUTIONS OF POLYPROPYLENE FIBER PROPERTIES ON THETENSILE RESPONSE OF FIBER ASSEMBLIES

The tensile response of some simple fibre assemblies is calculated, us ing the actual stress-strain relationships of constituent fibres. Thes e stress-strain relationships are obtained by a scaling procedure, wit h distributions of ultimate tensile properties and an average stress-s train curve as input. Two polypropylene fibres with different polydisp ersity index, but the same weight-average molecular weight and draw ra tio, are considered in this article. The fibre with the narrowest mole cular weight distribution (MWD) has about 30% higher average strength. On the other hand, if bundles with a large number of fibres are compa red, the strength of a bundle consisting of fibres with narrow MWD is less than 10% higher. The maximum strength of a random planar distribu tion of fibres is 36% and 44% of the average fibre strength, for fibre s with narrow and broad MWD, respectively. The strength of a chain-of- bundles decreases as the number of bundles increases, and as the numbe r of fibres in each bundle decreases. When the number of bundles is la rge, the strength of a chain-of-bundles containing fibres with broad M WD exceeds that of a chain containing fibres with narrow MWD. The asse mblies considered in this article illustrate effects in real assemblie s, such as non-woven fabrics. They also provide references for the ten sile properties of real assemblies.