Short fibre reinforced cores and their sandwich panels: Processing and evaluation

Abstract

Natural fibre composites (NFCs) that are replacing their synthetic counterpart in certain engineering sectors are often being underutilised, in mainly non-structural applications. Hence, in the view of adding value to current natural fibre composites, a relatively new concept of hollow cores fabricated from NFCs, has been investigated in this study. Thin continuous rolls of NFCs were produced in conical twin screw extruders which were then thermoformed into half hexagonal or sinusoidal profiles. The forming characteristics of the composites have been experimentally examined using single curvature V-bending experiments. The corrugated profiles were stacked and then bonded using ultrasonic methods to form cores for sandwich panels. The bond quality at the nodes of the cores has been experimentally determined using single-lap shear test. The mechanical properties such as compression and shear behaviour of the cores were determined by subjecting them to compressive and flexural loads, respectively. Sound absorption characteristics were determined using a standing plane wave impedance tube and the energy absorption capability was measured by subjecting the cores to quasi-static compressive loads until densification. The composites displayed good forming characteristic at the higher end of forming speed (500 mm/min) and temperatures closer to the melting temperature of the polymer matrix. The specific mechanical property values of the reinforced honeycombs after reinforcing the cell walls were more than twice of those of the un-reinforced cores. The energy absorption experiments revealed that the cores could be compressed to over 80% of their initial heights at a more or less steady stress making them suitable for packaging applications. The characteristic sound absorption of these panels at particular frequencies, coupled with good mechanical properties, make them eco-friendly and suitable in automobile, aerospace, packaging and building/construction industries.