Influence of temperature on the creep behaviour by macroindentation of Cocos nucifera shells and Canarium schweinfurthii cores (bio-shellnut wastes in Cameroon)

Abstract

The aim of this study was to show how temperature modifies the mechanical characteristics of the Cocos nucifera (CN) shells and the Canarium schweinfurthii (CS) cores. The test consisted in performing an instrumented macroindentation on prismatic specimens in an adiabatic chamber; the indentation carried out according to four temperature ranges (30 °C, 50 °C, 70 °C, 90 °C). The Oliver and Pharr method is used for the analysis of mechanical parameters in indentation: reduced Young’s modulus, hardness, creep coefficient. These parameters have enabled to estimate indirect characteristics such as toughness and ultimate mechanical stress to be obtained. The creep data are simulated to have the rheological model to these materials by considering the statistical criteria. As a global observation, when the temperature increases, the mechanical parameters decrease; although CN is more sensitive to the temperature gradient than CS, these 2 materials show performances that allow them to be classified as engineering polymer materials according to the Ashby diagram.