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The goal of this study was to fibrillate cellulose from micro to nano scale and evaluate how these microfibers and nanofibrils affected the mechanical and thermal properties of thermoplastic polyurethane. The source of cellulosic material was hard wood cellulose fibers and the fibrillation was done with a high pressure homogenizer. The composite materials were prepared using compression moulding, by stacking the cellulose fiber mats between polyurethane films. The results showed that both microfibers and nanofibrils reinforced the polyurethane and provided better heat stability. The addition of 16.5 wt% of cellulose nanofibrils to PU increased the strength nearly 500% and the stiffness by 3000%. These results are very promising in terms of obtaining fibrils with a novel processing method and by improving the mechanical and thermal properties of polyurethane. This is expected to expand the application areas of polyurethanes.

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Sandwich composites with a polyurethane foam (PUF) core have become a versatile set of materials with applications ranging from basic construction elements to advanced engineering materials. This diverse range of applications has provided these sandwich materials with a distinctive position in today's engineering world. This review focuses on the broad research that has been carried out on PUF core‐based sandwich composites over the years—especially in the last decade. Thorough details have been presented focusing on basic PUF core sandwich structures, advanced PUF core sandwich composites with different kinds of reinforcements and complex structures such as hybrid sandwich panels. All the research presented here has been categorized carefully, such as the types of materials used in various studies, the types of reinforcements and testing techniques used, including mechanical, electrical, dynamic, thermal and acoustic methods etc. Comparisons have also been made based on similar materials, similar testing procedures and similar application areas. Research areas have been highlighted by giving a deep insight into the most promising research, manufacturing techniques and improvement procedures. Major consumption areas and application sectors for PUF core sandwich composites have also been discussed in this review. Finally, conclusions have been made based on the results found from a literature investigation.

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