Determination of shear strength of additively manufactured poly lactic acid/flax fibre bio-composite via the iosipescu test

Abstract

The need to reduce CO2 emissions is leading to the search for alternatives to the manufacture of products from petrochemical sources. One of these alternatives is polylactic acid a bio-sourced, and biodegradable material, which is expected to be one of the most widely used materials in the forthcoming years. Recently, the feasibility of enhancing the mechanical characteristics of the PLA, by adding the flax fibre was demonstrated. Flax fibers are becoming an ideal alternative in reinforced polymer composites, thanks to the energy-intensive processing required to elaborate synthetic fibers. Flax fibers are not only recyclable and bio-degradable but also have excellent mechanical characteristics. However, the mechanical properties of flax fibre-reinforced polylactic acid composites, obtained by additive manufacturing techniques, are not well known. In the first part of this study, the quality of the Iosipescu shear experiment is examined with full-field strain measurements. In the second part, the in-plane shear response of manufactured flax fibre reinforced polylactic acid composites notched with the machining process and additive manufacturing technique are compared. This last makes it possible to evaluate the influence of the printing conditions and in particular the shell layers (contour) on the mechanical characteristics. It was perceived that the fully 3D printed specimens had a greater shear strength (+50.47%) and shear modulus (+44.68 %) than machined notch specimens. The fully 3D printed specimens count with the presence of a contour that rounds the vertices of the notches, reducing the stress-concentration factor, whereas in machined notch specimens, such contour was removed.