Mechanical properties of castor-oil polyurethane laminates reinforced with papaya bast fibre cellular layers

This work aims to manufacture and characterise a bio-composite material reinforced with natural papaya fibres using castor-oil polyurethane as the matrix phase. Samples are fabricated through hand lay-up and uniaxial compaction. Papaya fibres are extracted as laminas of a honeycomb-like structure, whose elongated cells line up in a single preferred direction. These laminas present a set of quasi-periodic holes along its surface, owing to the emergence of stems during the growing cycle of the plant. The influence of these holes on the mechanical properties of the laminates was investigated, as well as different morphologies (without holes, alternating holes, coincident holes and randomly oriented ground fibres (length ranging from 5-20 mm). The data are analysed via  Analysis of Variance (ANOVA) to assess the influence of the different morphologies on the tensile and flexural modulus and strength of the fabricated composites. Results reveal the potential of papaya fibres as a reinforcement phase in polymeric composite materials.