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Multiple scale study of hydrothermal degradation in the interfacial regions of flax fiber/bio-based polyurethane composites

Yunlong Jia, Bodo Fiedler

?Bio-composites have become more popular in a variety of applications in recent years. Bio-composites have been subjected to a lot of research in order to enhance their performance. The optimization of interfacial characteristics is one of the most essential aspects. Natural fibres' inherent hydrophilic characteristics not only create matrix incompatibility, but also render the interfacial areas extremely vulnerable to weathering impacts. Long-term deterioration of the interfacial areas, which is one of the least known components of bio-composites, may be caused by changes in ambient temperature and humidity. The goal of this research is to learn more about hydrothermal degradation and how it affects the interfacial characteristics of flax fiber/bio-based polyurethane composites. Experiments were carried out on two different scales. Single yarn fragmentation experiments were used to focus on the fiber/matrix interactions in a reliable fashion. To examine the effects of deterioration at the size of composites, corresponding unidirectional tensile tests were conducted. The deterioration caused by hydrothermal impacts was shown to decrease interfacial adhesion between flax fibres and matrix. The results from the two scales are highly correlated. Indicators from single yarn fragmentation tests, including as fragmentation development, fragmentation length distributions, and fracture forms, can accurately represent degradation in the interfacial areas. Water absorption and desorption both induce deterioration of fiber/matrix interactions, which is surprising
Nature succeeds in producing hybrid materials with extraordinary mechanical properties, such as high strength toughness, suited to the unique demands of biological systems, by mixing biopolymers and minerals into hierarchical nanoscaled structures. Complex biological structures that exhibit self-assembly processes and indicate a significant role for nanostructuration and nano-objects fascinate and motivate researchers in the creation of new engineering materials in this regard. Bio-inspired materials have already been studied in a variety of engineered materials that imitate natural systems including nacre, tooth, bone, and wood. In practise, it appears that these designs, through nanostructuration and the creation of a "hierarchical architecture," change stress transmission processes inside the material and increase its strength and fracture toughness.