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This study explores the potential of using underutilized materials from agricultural and forestry systems, such as rice husk, wheat straw, and wood strands, in developing corrugated core sandwich panels as a structural building material. By leveraging the unique properties of these biobased materials within a corrugated geometry, the research presents a novel approach to enhancing the structural performance of such underutilized biobased materials. These biobased materials were used in different lengths to consider the manufacturing feasibility of corrugated panels and the effect of fiber length on their structural performance. The average lengths for wood strands and wheat straws were 12–15 cm and 3–7.5 cm, respectively, while rice husks were like particles, about 7 mm long. Due to the high silica content in rice husk and wheat straw, which negatively impacts the bonding performance, polymeric diphenylmethane diisocyanate (pMDI), an effective adhesive for such materials, was used for the fabrication of corrugated panels. Wood strands and phenol formaldehyde (PF) adhesive were used to fabricate flat outer layers. Flat panels were bonded to both sides of the corrugated panels using a polyurethane adhesive to develop corrugated core sandwich panels. Four-point bending tests were conducted to evaluate the panel's bending stiffness, load-carrying capacity, and failure modes. Results demonstrated that sandwich panels with wood strand corrugated cores exhibited the highest bending stiffness and load-bearing capacity, while those with wheat straw corrugated cores performed similarly. Rice husk corrugated core sandwich panels showed the lowest mechanical performance compared to other sandwich panels. Considering the applications of these sandwich panels as floor, wall, and roof sheathing, all these panels exhibited superior bending performance compared to 11.2 mm- and 17.42 mm-thick commercial OSB (oriented strand board) panels, which are commonly used as building materials. These sandwich structures supported a longer span than commercial OSB panels while satisfying the deflection limit of L/360. The findings suggest the transformative potential of converting renewable yet underutilized materials into an engineered concept, corrugated geometry, leading to the development of high-performance, carbon-negative building materials suitable for flooring and roof applications. [ABSTRACT FROM AUTHOR]

Rice husks, a byproduct of rice milling, were used to develop composite boards. Different processing methods, grinding, and treating with sodium hydroxide (NaOH), were adopted to improve the bonding and mechanical performance. NaOH solution was prepared at 5% (wt/v) concentration. The effect of different adhesives, phenol formaldehyde (PF), and polymeric diphenylmethane diisocyanate (pMDI), was evaluated. Rice husks mixed with resin were hot pressed to the target density of 768 kg/m3 and thickness of 12.7 mm. Specimens cut from these flat panels were submitted to bending, internal bond, water absorption, and thickness swelling tests. Results revealed that chemical treatment with NaOH significantly improved fiber-to-fiber bonding of rice husks. Internal bond strength of specimens made from chemically treated rice husks increased at least 1000% compared to others. Considering the mechanical properties and water uptake, rice husk boards fabricated with unprocessed rice husks and pMDI showed a better performance. [ABSTRACT FROM AUTHOR]