Bio-based sandwich beams made of paper honeycomb cores and flax FRP facings: Flexural and shear characteristics

Abstract

Sandwich composite panels have been used in construction as building envelopes and cladding systems. The sandwich composite used today are mainly made of conventional synthetic foam cores and synthetic fiber-reinforced polymer (FRP) facings, typically made of glass or carbon fibers and synthetic polymers. With increasing environmental consciousness, it is important to develop sustainable building materials to replace conventional building materials with more sustainable materials such as bio-based fibers and polymers. There is lack of studies on sandwich composites made of bio-based materials for both core and facings. In this study, 18 sandwich beam specimens (1200 mm long and 100 mm wide) made of flax FRP facings and 75 mm thick paper honeycomb core were fabricated and tested under three-point bending. The parameters of the tests were facing thickness (1, 2 and 3 layers of flax FRP) and core types (hollow and foam-filled). It was found that the paper honeycomb has comparable performance with lighter weight to other synthetic counterparts and foam-filling was effective in improving the performance of the core and sandwich beams. In addition, as the nonlinear behavior of the specimens was evident, a new analytical model was developed based on the material nonlinearity of both facings and core materials to predict the test data and perform a parametric study. Overall, the bio-based sandwich system showed substantial potential to be used for building applications with much less environmental footprints in comparison with other synthetic counterparts.