Thermomechanically bonded spunbond nonwoven fabrics contain discrete bonds that are formed by melted and fused fibers. Through equi-biaxial tensile testing and simultaneous image capture, the mechanical response of individual bonds was studied through loading in the preferential fiber direction, the machine direction, and in the direction that is perpendicular, the cross direction, of the fabric web. Independent biaxial force and displacement data were collected and analyzed, and the maximum force and stiffness of the bonds in the machine and cross directions were found to be statistically different. After scaling the maximum force and stiffness by a relative basis weight parameter, a fiber orientation parameter, and the width of the bond itself, the peak force and stiffness in the machine and cross directions were found to no longer be statistically different. This indicates that basis weight, fiber orientation, and bond size dictate the biaxial mechanical behavior of the bonds. Furthermore, significant fiber debonding was observed in all the bonds tested, effectively suggesting bond disintegration into the individual component fibers during testing. Digital image correlation, using the captured images, was utilized to calculate local and average Eulerian strains of the bond during the initial stages of the test. The strain experienced by the bonds in the machine direction was always positive and increasing as the biaxial load increased. The strain in the cross direction, however, experienced increasing and decreasing strain. Local strain maps revealed the highly inhomogeneous strain response of the bonds under biaxial loading. / Master of Science / For numerous industrial and consumer applications, such as the medical, automotive, packaging, and consumer goods, nonwoven fabrics are often thermomechanically bonded at discrete bond locations in patterns appropriate for the intended use. To produce the nonwoven, fibers are extruded onto a belt and the mat of fibers is passed through a calendar roll to form the thermomechanical bonds. As the fibers move on the belt, there is a preferential fiber direction parallel to the belt. Mechanical biaxial tensile tests were performed on nonwoven sheets in order to gain insight into the response parallel and perpendicular to the preferential fiber direction. Force and displacement data were collected and the maximum force and stiffness response parallel to the preferential fiber direction were found to be significantly higher than perpendicular to the preferential fiber direction. Strain measurements were also performed to examine the local strain of the bonds. Knowledge of the biaxial tensile behavior of bonds in nonwovens allows manufacturers to make informed decisions about the ultimate final application of the nonwoven.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/86517 |
| Date | 29 June 2017 |
| Creators | Wijeratne, Roshelle Sumudu |
| Contributors | Mechanical Engineering, De Vita, Raffaella, Dillard, David A., Nain, Amrinder, Leonessa, Alexander |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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