It is a well established fact that the strength of a yarn and its variance are determined by the tensile properties of constituent fibers. However, the results from either single fiber or bundle tensile testing alone do not predict the yarn tensile properties well due to the fact that the bundle strength efficiencies and variances are functions of bundle size. A theory was developed to predict the strengths and variances of small fiber bundles in terms of the bundle size and the single fiber tensile properties. Cotton fibers were tested on a Mantis^®; single fiber tester, and the results were applied in validating the theoretical models developed. The tensile properties of small bundles were also obtained by superposition of single fiber load-elongation curves from MantisR tests.

The results from the model showed an excellent agreement with the results of computer simulation of bundle strength, its standard deviation and CV.