Experimental and numerical investigation of damage and mechanical property retention by bio-composite plastic made with flax or pinewood fiber and aged by exposure to ultraviolet light

The objective of this study was to compare two types of natural short fibers, one lignin-rich and one lignin-poor, as reinforcing filler of bio-composite plastic in accelerated aging experiments. Short natural-fiber-reinforced plastic composites of flax fiber or pinewood fiber (30 % by weight) were injected and then exposed to ultraviolet (UV) light with and without moisture for up to 1440 h. Color, roughness, and mechanical properties were then evaluated using colorimetry, confocal laser imaging, tensile tests, and drop-weight tests. Damage to the bio-composites was monitored using the acoustic emission technique during tensile testing. The response during impact tests was simulated using the finite element method. Results showed that flax-fiber-reinforced polypropylene exhibited superior properties before aging, but experienced greater loss of these properties after aging, particularly under moist conditions. The numerical model was found to be in good agreement with the experimental results.