Evidence and potential explanation of the influence of fiber length on the High Volume Instrument measurement of cotton fiber strength

Abstract

This study explores the influence of cotton fiber length characteristics on the High Volume Instrument (HVI) strength measurement. A set of cotton samples cut at different lengths from a common parent sliver was used. HVI strength data exhibited a consistent trend as a function of the fiber length properties. This data was analyzed using the working hypothesis that the HVI estimates the total mass of fiber at a position between the jaws, rather than the true mass, which contributes to the breaking force. A quantitative model was developed to correct for this overestimation based on the shape of the Fibrogram. It was demonstrated that the Fibrogram can be adequately modeled as a straight line in the region of the HVI strength measurement. Based on this, it was found that the required correction factor is a function of the mean fiber length and various geometrical parameters of the HVI instrument (i.e. (a) the distance from the base of the beard to the inside edge of the clamp nearest the base of the jaws, and (b) the actual position of the beard's fiber length determination relative to the clamping jaws). Importantly this correction factor is independent of the shape of the fiber length distribution. Application of this correction factor approach was able to remove the effect of fiber length on the corrected strength values. The same model was also applied to other published data and, again, a simple correction factor based on mean fiber length adequately ‘removed’ the observed bias.