Characterizing structural changes in point-bonded nonwoven fabrics during load-deformation experiments

Current efforts to establish links between processing conditions and the st ructure and properties of nonwoven fabrics in general, and for point-bonded (spot-bonded) nonwovens in particular, would be served significantly by in situ experimental visualization and measurement of the structural changes that occur during controlled deformation experiments. The features of a sim ultaneous "tensile testing/image acquisition" instrument that can serve thi s critical need are described in this report. The instrument is effective i n providing quantitative measures of the orientation distribution function (ODF) Of the fibers, the bond spot strain, the unit bond repeat pattern str ain, and the shear deformation of this unit cell as a function of applied m acroscopic deformation. It is also useful in determining the failure mode a s a function of the method of applying deformation to the nonwoven fabric. These features are exemplified through analysis of a point-bonded carded no nwoven, which is anisotropic in its fiber orientation distribution and in t he geometry and distribution of its patterned thermal bond spots.