How the Test Setup Can Affect Single Fiber Tensile Testing

Tensile testing is the most common method to investigate natural fibers. The fibers’ mechanical behavior can be considered non-linear and is influenced by viscoelasticity, plasticity, and environmental conditions. Very often such fibers are tested by gluing them with an adhesive onto a sample holder. Such a system consisting of a polymeric sample holder, adhesive, and natural fiber is complex and there is a risk that the mechanical response measured is a mix of the different contributions of those components. In this work, the key components for tensile testing of natural fibers ‒ sample holder and adhesive ‒ are investigated, to determine their influence on the measurement results. In order to isolate the influence of the measurement setup, the natural fiber is replaced with a platinum wire, which is purely linear-elastic. Hence all non-linear contributions from sample holder or adhesive can be identified. The main influence factor on the results was the glue used for fixating the fiber on the sample holder. Epoxy resin was found to be best suited. Taking these findings into account, a series of tensile tests was performed on cellulose-based natural fibers for demonstration but is applicable to any natural fiber.