Mechanical properties of aluminium reinforced with crushed gravel and coconut shell ash for various applications

Abstract

This work investigated the mechanical characteristics of Aluminium reinforced with coconut shell-ash and crushed gravel powder because pure Aluminium presents limitations due to its low tensile strength of less than 90 N/mm² under annealed conditions. To fabricate the composite, the present work utilized weight percentages of 4, 5, 7.5 and 10% for coconut shell ash powder (CSAp) and 5, 6, 7, and 7.5% for crashed gravel (CGp). The chemical analysis of the reinforcement materials was carried out using the scanning electron microscope coupled with the Energy dispersive x-ray analysis (EDX). The aluminium matrix composite was produced by a stir casting process at a firing temperature of 650 0C. These composite samples were prepared and subjected to microstructural and mechanical properties tests using the scanning electron microscopy (SEM) and the universal testing machine (UTM). Microstructural analysis revealed the presence of significant voids that were identified with dark patches within all the samples and the presence of striations that resulted from the irregular and non-uniform distribution between the matrix and the reinforcement materials. The mechanical property test results revealed that the composite sample S5 only reinforced with 5 wt% of crushed gravel exhibited the highest tensile strength of 157.5 MPa but with the smallest compressive strength of 111.13 MPa. Sample S2 which was reinforced with equal 7.5 wt% of crushed gravel and coconut shell ash produced the highest Rockwell’s hardness of 117 HRB with the least value of 66 HRB produced by sample S1. Sample S4 that was reinforced with 5 wt% of coconut shell ash only, produced the highest compressive strength of 355.83 MPa. Additionally, sample S3 exhibited the maximum elongation among the tested samples, with a value of 9.59%. With the exception of AMC sample 4, all other fabricated AMCs exhibited tensile strengths above that of pure Aluminium (90 MPa), hence the fabricated AMC can be used for various structural applications in the building and construction industries.