Failure mechanisms in unidirectional self-reinforced biobased composites based on high stiffness PLA fibres

Biobased self-reinforced polymer composites using polylactic acid (PLA) were developed. To create PLA based self-reinforced composites (SR-PLA) with improved properties, first high stiffness PLA fibres with high melting temperature were produced by optimising the melt spinning process parameters. Unidirectional SR-PLA composites with enhanced stiffness were obtained, comparable to the commercially available self-reinforced polypropylene composites.

The failure strain of the composites was several times higher than the failure strain of the compact PLA. An increased strength, compared to the compact PLA, was obtained but the increase was less pronounced. To understand the behaviour of unidirectional self-reinforced PLA composites, in-situ tensile tests were performed inside the chamber of an Environmental Scanning Electron Microscope.

The damage initiation and evolution under tension was monitored. It was found that the primary limiting strength factor is the high brittleness of the compact (matrix) PLA.