Sandwich panels made of aluminium skins and gapped-bamboo ring core

Sandwich panels have been used for sporting goods to load-bearing components. Whenever possible, new guidelines in engineering design have driven towards sustainable and biodegradable materials, minimising disposal costs and environmental impact. This work describes the physical and mechanical properties of sandwich panels made of aluminium skins, honeycomb cores based on bamboo rings and castor oil biobased adhesive. Sandwich panels consisting of bamboo rings (Ø30 mm) mounted on hexagonal packing are placed (i) side by side and (ii) in spaced spans. The latter is an attempt to reduce weight and increase specific mechanical properties. To better understand the gap effect, the sandwich dimensions are designed to generate significant shear stresses in the core. Gapped-bamboo ring core increases internal voids by about 40%, leading to reductions of 26%, 63% and 59% in equivalent density, maximum load and flexural strength, respectively. Spacing also reduces facing stresses, and core shear modulus, which can be attributed to the loss of the interlocking effect promoted by bamboo rings placed side by side. However, the specific flexural modulus (rigidity) of panels with the gap ring core is increased by 37% compared to the pristine condition, when shear deformations tend to be neglected.