Experimental investigations on green composite sandwich made of flax and agglomerated cork

Abstract

Many researchers are striving to implement lightweight materials in their applications to achieve energy savings. Composite sandwiches are becoming more and more popular in structural and non-structural applications, mainly due to their lightweight and uncompromising performance. Most of the composite sandwich structures nowadays are made of non-renewable resources, which need extensive amounts of energy for production generating excessive amounts of carbon dioxide which impacts the environment. End life disposal is also a hindrance due to their nonbiodegradable nature. These aspects have led the material experts to explore the possibilities of using natural materials as constituents in composite sandwiches which has benefits in terms of natural availability, biodegradability, and cost. Hence, a green composite sandwich might be the material of the future which will satisfy both the performance and environmental concerns. The objective of this research work is to investigate mechanical, thermal, sound absorption, vibration damping and biodegradable behaviour of the newly developed green composite sandwich made of flax and agglomerated cork. In this work, flax fibre in woven form is used as skin reinforcement and agglomerated cork with three different densities (240, 280, and 340 kg/m3 ) is used as a core in the green composite sandwich. Along with this, glass and flax/glass skin reinforced composite sandwiches are also manufactured for comparison purpose. The composite sandwiches are manufactured by vacuum bag moulding due to their benefit of getting higher volume fraction of fibre, and improved adhesion between layers compared to hand lay-up method. In order to understand the mechanical behaviour of composite sandwich, flatwise tensile test, flatwise compressive test, edgewise compressive test, flexural test and drop weight impact test were carried out as per the ASTM standards and the strength of each sample was recorded. The test results revealed that the flax fibre reinforced composite sandwich (FEC) with core density 340 kg/m3 has higher specific flatwise tensile strength, specific flatwise compressive strength, and specific flexural strength than glass fibre reinforced composite sandwich (GEC) with core density 340 kg/m3 . But in the edgewise compressive test and drop weight impact test, FEC has a slight decrease in the specific edgewise compressive strength and perforation energy. Effect of water absorption on the mechanical properties was also determined by exposing the samples in a humid environment. The presence of moisture content in the samples decreases the specific flexural strength of FEC by 27-42 % in contrast to a mild impact in GEC by 14-33 % due to the existence of natural fibre in the FEC. newline