Experimental Investigation of Spherical Core Sandwich Structure by Beam Flexure

Abstract

Honeycomb structures are the most widely used sandwich structures as it provides material with minimal density and relative high out-of-plane compression properties and out-of-plane shear properties. Though the properties are substantial, the manufacturing of honeycomb structure is difficult. In this study, GFRP sandwich was selected for investigation as it is widely used in aerospace structural applications due to its high strength-to-weight ratio. A novel (spherically cored) sandwich structure of two different models, namely regular spherical and inverted spherical, was designed and fabricated. The sandwich structures were made with vinyl ester resin and two different GF reinforcements, namely woven glass fiber fabric and chopped strand fabric by hand lay method. The diameter of the spherical core was fixed as 16 mm, whereas two different pitch distances of 24 and 32 mm were used. The core shear properties and facing fracture stress of these eight variants of spherical cored sandwich specimens were tested using three-point bend test. The test result indicated that the regular spherical structure model with chopped strand and pitch of 24 mm possess a high core shear strength of 427 kPa which is more or less equivalent to honeycomb sandwich structure and facing fracture stress of 34 MPa. Whereas the regular spherical sandwich structure made with woven 24 mm pitch shows a low core shear strength of 79 kPa and facing fracture stress of 6.37 MPa.