Novel Applications of Aluminium Metal Matrix Composites

Advanced materials have offered the materials designer a wide range of options in the specification and selection of materials for various applications. Material properties are continually being improved to meet safety and operational standards in line with prevailing technological developments. Modern technological requirements, together with the consumers’ demands for systems and machines that are more energy efficient, stronger, light-weight, cost-effective, etc., dictate that the search for new and advanced materials will remain a subject of interest all the time. The difficulty in designing materials for such stringent specifications cannot be overstated, owing to the conflicting nature of these specifications. Aluminium metal matrix composites (AlMMCs) are a class of materials that have proven successful in meeting most of the rigorous specifications in applications where light-weight, high stiffness and moderate strength are the requisite properties. With a variety of reinforcement materials and flexibility in their primary processing, AlMMCs offer great potential for the development of composites with the desired properties for certain applications. In this review, the development, utilisation and future potential of AlMMCs in various industrial and commercial applications is discussed, together with the existing challenges hindering their full market penetration

Modeling and vibration analysis of twin-rotor system interconnected by a Hooke’s joint (Part A)

This paper explores the model for the analysis of two misaligned Jeffcott rotors flexibly-coupled through a Hooke’s joint. The aim is to present a transmission on non-linear shafts-coupling model subjected to elastic deformation. The model provides some insight into the transmission motion on misaligned rotor-system under the influences of unbalance and helps to understand the dynamic characteristics of the coupling twin-rotor system. Modelled results reveal that the unbalance and Hooke’s joint in the drive and driven shafts lead to alternating stress fields in the rotating shafts

Experimental setup for unbalance fault detection and vibration analysis in a cardan shaft (Part B)

This paper experiments a vibration measurement on a twin-rotor connected by a Hooke’s joints. An experimental set-up for vibration analysis and unbalance fault detection in rotating machinery has been conducted to reveal the unbalance effect in signal transmission of the interconnected shaft through Hooke’s joint. Vibrations signals were measured and analysed using the Fast Fourier Transform (FFT), orbit patterns and time displacement of each rotor centre, to extract the signature of the unbalance fault. The results indicate the accuracy of the discussed approach for the twin-rotor unbalances diagnosis in an interconnected shafts system through a Hooke’s joint

The Tensile and Flexural Properties of Treated and Untreated Sisal Fibre-Epoxy Resin Composites

Published ArticleThe influence of chemical treatment of sisal fibres through the subsequent processes of mercerisation (alkali treatment), then silane treatment and eventually acid hydrolysis on the fibres were investigated. The effect of the treated fibres on the tensile and flexural properties of their composites with epoxy resin were also studied. Scanning electron microscopy examination of the treated and untreated fibres showed that the subsequent processes of chemical treatment enhanced the removal of surface impurities and therefore increased the roughness of the fibre surfaces. It was concluded that this would avail an increased surface area on the fibre for interlocking with matrices and would therefore enhance adhesion of the two. Consistent to this conclusion, subsequent testing of treated fibre reinforced composites gave rise to higher values of tensile and flexural strength and toughness than the untreated fibre reinforced composites

Effects of Stress-Relieving Heat Treatment on Impact Toughness of Direct Metal Laser Sintering (DMLS)-Produced Ti6Al4V (ELI) Parts

Published ArticleThe impact toughness of as-built (AB) and stressed-relieved (SR) direct metal laser sintering-produced Ti6Al4V (ELI) was investigated using the standard Charpy impact test over the temperature range of 130 C to 250 C. Stressrelieving heat treatment was conducted at 650 C for a soaking period of 3 h in argon gas atmosphere. The results showed improvements in the impact toughness after stress-relieving heat treatment. Stress relieving also shifted the established ductile-to-brittle transition temperature to lower temperatures. Comparative analysis of the impact toughness values for AB and SR specimens at ambient temperature showed them to be 48% and 22% lower than recommended values for use in aircraft structures, respectively

Effect of Stress-Relieving Heat Treatment on the High Strain Rate Dynamic Compressive Properties of Additively Manufactured Ti6Al4V (ELI)

ArticleA study was undertaken on the compressive high strain rate properties and deformation behaviour of Direct Metal Laser-Sintered (DMLS) Ti6Al4V (ELI) parts in two separate forms: as-built (AB) and stress relieved (SR). The high strain rate compression tests were carried out using a Split Hopkinson Pressure Bar test system at ambient temperature. The average plastic strain rates attained by the system were 400 s1 and 700 s1. Comparative analyses of the performance (flow stresses and fracture strains) of AB and SR specimens were carried out based on the results obtained at these two plastic strain rates. Microstructural analyses were performed to study the failure mechanisms of the deformed specimens and fracture surfaces. Vickers microhardness test values were obtained before and after high strain rate compression testing. The results obtained in both cases showed the strain rate sensitivity of the stress-relieved samples to be higher in comparison to those of as-built ones, at the same value of true strain

A Review Of The State Of Research And Utilization Of Biomaterials In The Manufacture Of Composite Materials Todate

ArticleOver the last four decades composite materials, plastics and ceramics have been the dominant emerging materials. The volume and number of applications of composite materials has grown steadily, penetrating and gaining acceptance in new markets. Modern composite materials constitute a significant proportion of the engineered materials market, ranging from everyday products to sophisticated niche applications. While composites have already proven their worth as weight saving materials, the current challenge is to make them cost effective. This paper presents review on the worldwide state of research of biomaterials and their utilization in the manufacture of composite materials

Effect of Stress-Relieving Heat Treatment on the High Strain Rate Dynamic Compressive Properties of Additively Manufactured Ti6Al4V (ELI)

A study was undertaken on the compressive high strain rate properties and deformation behaviour of Direct Metal Laser-Sintered (DMLS) Ti6Al4V (ELI) parts in two separate forms: as-built (AB) and stress relieved (SR). The high strain rate compression tests were carried out using a Split Hopkinson Pressure Bar test system at ambient temperature. The average plastic strain rates attained by the system were 400 s−1 and 700 s−1. Comparative analyses of the performance (flow stresses and fracture strains) of AB and SR specimens were carried out based on the results obtained at these two plastic strain rates. Microstructural analyses were performed to study the failure mechanisms of the deformed specimens and fracture surfaces. Vickers microhardness test values were obtained before and after high strain rate compression testing. The results obtained in both cases showed the strain rate sensitivity of the stress-relieved samples to be higher in comparison to those of as-built ones, at the same value of true strain