In Situ Characterization of the Damage Initiation and Evolution in Sustainable Cellulose-Based Cottonid

Abstract

The usage of environmentally friendly materials based on sustainable resources is nowadays more important than ever, especially in technical applications. Cottonid is based 100% on cellulose, therefore sutainable and due to its excellent properties a promising alternative material in terms of eco-friendliness. Within this study, the deformation and damage behavior of two Cottonid variants, an industrial standard as well as the structurally optimized variant M60Z50, is characterized for the first time using innovative in situ testing techniques. Quasi-static tensile tests were comparatively performed in a scanning electron microscope as well as a microfocus computer tomograph, and the development of defects present in the initial condition of the materials were investigated on surface and in volume. In general, in the elastic region, no visible damage initiation on the surface and a decrease of overall void volume within the gauge length could be detected for Cottonid. When reaching the yield strength, cracks initiate on the surface at critical areas, like pores and microcracks, which propagate and assemble until total loss of structural integrity. Further, in the plastic region, an increase in void volume could be shown in the gauge length until final failure. Compared to an industrial standard, M60Z50 exhibits a clearly lower percentage in overall void volume and shows increased mechanical properties, like yield strength and ultimate tensile strength. The structural optimization of M60Z50 seems to result in a more sufficient bonding of the paper layers during the manufacturing process, which improves the deformation and damage behavior under quasi-static loading.