Lightweight sandwich panels with bamboo-ring cores and fiber cement facings

This is the authors' abstract. We don't add key points for this paper.

This study assessed lightweight sandwich panels composed of fiber cement facings, bamboo-ring cellular cores, and a bio-based polyurethane adhesive derived from castor oil. Phyllostachys aurea bamboo rings, potentially obtainable from the by-products of bamboo processing, were used as the core material. Although bamboo-ring cores have been studied with composite and metallic facings, their integration with fiber cement facings has not been systematically assessed, particularly regarding the effects of core arrangement, height, and adhesive bond-line thickness. To address this gap, a 2³ full-factorial design was adopted with two core arrangements (compact and gapped hexagonal), two core heights (20 and 30 mm), and nominal bond-line thicknesses (0.75 and 1.00 mm). The equivalent density and flexural responses varied mainly with core height and arrangement, whereas the bond-line thickness had a smaller effect within the investigated range. Among the tested configurations, panels with 20 mm cores exhibited higher apparent cross-section flexural strength and modulus, whereas panels with 30 mm cores exhibited greater flexural rigidity. The 20-C-0.75 configuration exhibited the highest apparent cross-section flexural strength (6.10 ± 0.14 MPa). In contrast, the 30-G-0.75 configuration exhibited the lowest equivalent density (0.55 ± 0.01 g/cm³), indicating a density–strength trade-off. Reducing the bond-line thickness from 1.00 to 0.75 mm decreased the polyurethane adhesive consumption by approximately 25%, while the bond-line thickness did not significantly affect the apparent flexural strength. The measured responses indicate the potential for further development of fiber cement-faced bamboo-ring sandwich panels and provide an initial processing–geometry basis for this panel concept.