The Influence of Strain Rate on Tensile Properties of Additive-Manufactured Wood-Based Polylactic Acid (PLA) (CR-Wood): an Experimental Investigation

External conditions such as strain rate and temperature influence the mechanical properties of materials. In this paper, the influence of strain rate on the tensile properties of an additive-manufactured polylactic acid (CR-Wood PLA) polymer is studied experimentally. The key mechanical properties, including tensile modulus, yield strength, and strain at fracture of the material are studied at the low (0.0091/s and 0.91/s) and the intermediate (1/s – 3.63/s) strain rate ranges. The experimental investigation revealed that the stress-strain relationship of the material is influenced by the strain rate, however, differently across the ranges. The yield strength improved with the increase in the strain rate until ἐ = 1.81⁄s. A further increment in strain rate slightly declined the yield strength. The tensile modulus showed a notable decrement, however, only near the transition between the low and intermediate ranges. On the other hand, the strain at fracture monotonically decreased with the strain rate at both ranges. The material underwent significant post-yield plasticity, and a stress whitening throughout the reduced section of the specimens during the low strain rate tests. At higher strain rates, the plasticity was limited, and the stress whitening was localized just at the fracture surfaces.