Recycling of Carica papaya trunk fiber plies: experimental and analytical characterization

The main aim of this work is to show that it is possible to use Carica papaya trunk fiber plies as honeycomb cores in sandwich structures. To achieve this, the plies were extracted using the traditional method (water retting). Chemical and physical characterization of the plies yielded 54% cellulose, 23% hemicellulose and 22% lignin, with a crystallinity index of 45.39% and a density of 0.644 g/cm³. SEM data showed a rough microfiber tangle. Mechanical tests produced a Young's modulus of 8.73 GPa, a stress at break of 58.98 MPa, a maximum elongation of 11%, a flexural modulus of 920.7 MPa, a stress at break in three-point bending of 7.36 and 5.72 MPa in four-point bending and a shear stress of 0.32 MPa. Although analytical calculation did not take the microstructure into account, the results were 4.9% lower than the experimental results, so Gibson's model provides a reliable approach. Following these results and their comparison with materials available on the market, papaya fiber plies have a place in sandwich materials as honeycomb cores.