Microscopic observations during longitudinal compression loading of single pulp fibers

Paperboard components (linerboard adn corrugating medium) fail in edgewise compression because of failure of single fibers, as well as fiber-to-fiber bonds. While fiber-to-fiber- bond failure has been studied extensively, little is known about the longitudinal compression failure of a single fiber. In this study, surface alterations on single loblolly pine kraft pulp fibers were observed during compurssion in a devise built for use in the scanning electron microscope. Distinct changes were observed in the fibers subjected to compression loading, including dislocations (slip planess), loosening of the fibrils, piling up of the bigrilar walls, and fibril fracture when loaded in compurssion. From these observations, the apparent failure sequence for a single pulp fiber is (a) formulation of dislocations, (b) loosening of the fibrils, piling up of the fibrillar walls, and eventual fibril fracture, and (c) coalescence of fractures, causing further reduction in fiber wall strength and eventual failure of the fiber. Direct observation of fibers under compression load suggests that sgrenghtening of the fiber wall, such as by use of chemical additives, could lead to improved fiber mechanical properties.