An Instrumented Macro-Indentation Method for Determining the Mechanical Properties of Coconut Shell (Coco Nucifera of Cameroon)
Résumé
An instrumented macro-indentation test was used to determine the viscoelastic parameters and hardness of the shell of Coco Nucifera from Cameroon in order to promote their use in the manufacture of abrasives. Samples measuring 10 mm x 10 mm x 3 mm were cut out from the bottom of the fruit, close to the natural indentations (the eye) of an approximately round-shaped fruit. The indentation load ranged from 50 to 500 N with an increment of 50 N. A comparator with digital display and a camera attached to the machine measured the total penetration and rate of penetration. The Oliver and Pharr indentation model and Hertz contact theory were used to determine the Young's modulus, hardness and creep ratio of coconut shells. Young's modulus determined in the polar zone was 3.52x10 3 MPa and 1.45x10 3 MPa in the equatorial zone. The hardness was 1.16x10 2 MPa in the polar zone and 0.7x10 2 MPa in the equatorial zone. The creep ratio was 16 in the polar region and 8 in the equatorial zone. Validation of the procedure and results will be done with indentation tests on a kind of wood: Azobé (Lophira alata). Introduction. Coconut Shell of Coco Nucifera (CSCN) is a product of the coconut tree (Coco nucifera) which is exploited for the valuable flesh (copra) enclosed in the hard shell. Important quantities of CSCN are generated during the production of copra [1]. The CSCN alone occupies about 25% by weight of the nuts and with about 54 million tons of coconuts produced annually worldwide [2], an estimated 13.5 million tonnes of CSCNs is generated. A small part of these shells is used in the production of activated carbon. [3]. However, most of CSCN is not used, presenting a challenge for solid waste management [4]. Usually the CSCN is simply discarded in nature with negative environmental impact (occupying land that could otherwise be used for agriculture, breeding sites for mosquitos). In recent years, the instrumented indentation test has been used as an alternative method for determining mechanical properties of materials [5]. The hard nature and the abrasiveness of the shell makes it a potential food processing material. A good knowledge of the properties of this hull allows it to be used as a green alternative in agro-processing tools to plump goods such as beans, maize and groundnuts, otherwise like abrasives for woods. Preliminary characterisation of this shell
Origine : Accord explicite pour ce dépôt
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