Cellulose sandwich composites with tube-reinforced foam cores

Lightweight porous cellulose materials, in particular pulp fibre foams, face challenges in achieving suitable mechanical properties while maintaining sustainability. Porous cellulose structures were developed by inserting pulp fibre pins or paper tubes into pre-perforated pulp fibre foams to form a sandwich structure with kraft liner paper deck sheets using a simple and scalable manufacturing process. The resulting porous cellulose composite structures, with densities ranging from 80 kg/m³ to 177 kg/m³, were mechanically characterised under compression, three-point bending, and double lap shear loading. We demonstrate that tube-reinforced configurations outperformed perforated pulp fibre foams in stiffness and strength, showing a significant improvement of 10,300% in compressive, 1500% in flexural, and 350% in shear modulus compared to perforated pulp fibre foams. We showed that the mechanical performance of pulp-based materials can be controlled by structural design rather than material modification, providing a viable strategy to overcome mechanical limitations of cellulose fibre foams.