Rapid innovation in nanotechnology in recent years enabled development of advanced metal matrix nanocomposites for structural engineering and functional devices. Carbonous materials, such as ...graphite, carbon nanotubes (CNT's), and graphene possess unique electrical, mechanical, and thermal properties. Owe to their lubricious nature, these carbonous materials have attracted researchers to synthesize lightweight self-lubricating metal matrix nanocomposites with superior mechanical and tribological properties for several applications in automotive and aerospace industries. This review focuses on the recent development in mechanical and tribological behavior of self-lubricating metallic nanocomposites reinforced by carbonous nanomaterials such as CNT and graphene. The review includes development of self-lubricating nanocomposites, related issues in their processing, their characterization, and investigation of their tribological behavior. The results reveal that adding CNT and graphene to metals decreases both coefficient of friction and wear rate as well as increases the tensile strength. The mechanisms involved for the improved mechanical and tribological behavior is discussed.
Aluminum/graphite (Al/Gr) composites have been used as self-lubricating materials due to the superior lubricating effect of graphite during sliding. This paper summarizes various tribological aspects ...of self-lubricating aluminum composites. The influence of various factors such as (a) material factors, graphite size and volume fraction, and (b) mechanical factors, applied load and sliding speed on the tribological properties of self-lubricating aluminum composites, is discussed. Furthermore, the tribological properties of self-lubricating composites as a function of these parameters and the active wear mechanism involved in various systems are discussed. Bringing self-lubricating composites into different operating systems is a solution to reduce the use of external toxic petroleum-based lubricants in sliding contacts in a way to help the environment and reduce energy dissipation in industrial components for strategies toward sustainability and energy efficiency.
Data-driven methods including machine learning (ML) algorithms can yield a better understanding of how tribological and material properties correlate. Correlations of friction and wear of aluminum ...(Al) base alloys with their material properties (hardness, yield strength, tensile strength, ductility, silicon carbide content), processing procedure, heat treatment, and tribological test variables (sliding speed, sliding distance, and normal load) studied using traditional and data-driven approaches. Five different ML algorithms, K Nearest Neighbor (KNN), Support Vector Machine (SVM), Artificial Neural Network (ANN), Random Forest (RF), and Gradient Boosting Machine (GBM) applied to experimental tribological data to predict the coefficients of friction (COF) and wear rates. Through performance analysis, we demonstrated that the ML models can satisfactorily predict friction and wear of Al alloys from material and tribological test variables data. Comparative analysis of model performance illustrated that RF outperformed other ML models in wear rate prediction, while KNN exhibited the best performance in COF prediction. Feature importance analysis further revealed that normal load, hardness, and sliding speed have the maximum influence in predicting the wear rate of the alloys. The variation in hardness of the alloys and sliding distance influenced the COF prediction the most.
•Five different Machine Learning (ML) algorithms used to correlate tribological and material properties of Al alloys.•ML models can satisfactorily predict friction and wear of Al alloys.•Comparative analysis of different algorithms performed.•Materials properties were analyzed for their importance for predicting the wear rate and friction.
•The curing kinetics of prepared composites were studied.•The fiber surface modification as coupling agent of CNFs in bio-based epoxy improved the curing of the resin by reducing the activation ...energy at very high temperature (130°C).•Enhanced tensile strength of the composites reinforced by silyliated CNFs confirmed.•Composites reinforced by cellulose fibers have lower coefficient of friction and wear.•The uniform tribo-layer formed during sliding facilitated to reduce ‘direct contact’ and improve tribological properties.
The development of bio-based composites is essential in order to protect the environment while enhancing energy efficiencies. In the present investigation, the plant-derived cellulose nano-fibers (CNFs)/bio-based epoxy composites were manufactured using the Liquid Composite Molding (LCM) process. More specifically, the CNFs with and without chemical modification were utilized in the composites. The curing kinetics of the prepared composites was studied using both the isothermal and dynamic Differential Scanning Calorimetry (DSC) methods. The microstructure as well as the mechanical and tribological properties were investigated on the cured composites in order to understand the structure-property correlations of the composites. The results indicated that the manufactured composites showed improved mechanical and tribological properties when compared to the pure epoxy samples. Furthermore, the chemically modified CNFs reinforced composites outperformed the untreated composites. The surface modification of the fibers improved the curing of the resin by reducing the activation energy, and led to an improvement in the mechanical properties. The CNFs/bio-based epoxy composites form uniform tribo-layer during sliding which minimizes the direct contact between surfaces, thus reducing both the friction and wear of the composites.
Natural fiber reinforced polymer composites have emerged as a potential environmentally friendly and cost-effective alternative to synthetic fiber reinforced composites. Therefore, in the past ...decade, a number of major industries, such as the automotive, construction and packaging industries, have shown a considerable interest in the progress of new natural fiber reinforced composite materials. The availability of natural fibers and the ease of manufacturing have tempted researchers to study their feasibility of their application as reinforcement and the extent to which they satisfy the required specifications in tribological applications. However, less information concerning the tribological performance of natural fiber reinforced composite material is available in the literature. Hence, the aim of this bibliographic review is to demonstrate the tribological behavior of natural fiber reinforced composites and find a knowledge about their usability for various applications that tribology plays a dominant role. This review presents the reported work on natural fiber reinforced composites with special reference to the type of fibers, matrix polymers, treatment of fibers and test parameters. The results show that composites reinforced with natural fibers have an improvement in tribological properties and their properties are comparable with conventional fibers. In addition, fiber treatment and fiber orientation are two important factors can affect tribological properties where treated fibers and normal oriented fibers exhibit better friction and wear behavior. This review is trying to evaluate the effect of test parameter including normal load and sliding speed on tribological properties, and the results vary based on type of reinforcement. Generally, due to their positive economic and environmental aspects, as well as their good tribological properties, natural composites are showing a good potential for employing in several applications.
We study wear and friction of dry and lubricated aluminum-graphite composites and the transition between lubrication regimes. Using Principal Component Analysis, we perform dimensionality reduction ...for the 14 material and tribological variables to find clusters in friction and wear data. Five standalone and one hybrid supervised regression models were developed to predict friction and wear of lubricated composites. ML analysis identifies lubrication condition and lubricant viscosity as the most important variables. Unlike dry, graphite content has a reduced impact on the tribological behavior with liquid lubricants. The incorporation of graphite in the matrix of aluminum alloys enables them to run under boundary lubrication and run for more extended periods with lower friction even after the lubricant is drained out.
•Machine Learning (ML) algorithms used to correlate friction, wear and material properties of Al-Graphite composites.•ML models can satisfactorily predict friction and wear of Al-Gr composites.•Comparative analysis of different algorithms performed.•The transition between different liquid lubrication regimes and to dry solid lubrication are studied.
The effect of graphene on the material properties, friction, and wear of self-lubricating aluminum-based metal matrix composites (MMC) was compared with the effect of graphite as the reinforcement. ...Notable enhancement of mechanical properties and friction and wear performance was observed with graphene addition. Statistical analysis suggested that a much lesser amount of graphene reinforcement can produce friction and wear performance similar to that of aluminum MMCs with a higher amount of graphite. Five machine learning (ML) regression models were developed to predict the wear rate and coefficient of friction (COF) of aluminum-graphene MMCs. ML study suggested that the weight percent of graphene, loading conditions, and hardness had the largest influence on the wear and friction of aluminum-graphene composites.
Fly ash (FA) is one of the particulate wastes generated during combustion of coal in thermal power plants. Around 110 million tons of FA is generated in the USA every year, and 60% of it is deposited ...in landfills. Utilization of FA can create value for this waste material and also help the environment. FA is essentially a mixture of metal oxides that can be used as a filler reinforcement in metal and polymer composites. FA as a filler material reduces the amount of metals and polymer, reducing embodied energy. Hollow FA particles, called cenospheres, can provide the advantage of low density in composites as well as higher hardness and strength. FA also reduces the coefficient of thermal expansion. This article provides a brief review to capture the state of the art on the mechanical and tribological behavior of composites reinforced with FA to identify the possible benefits of using this waste material. The corrosion performance of metal matrix FA composites is also explored. Future perspectives in this field are discussed based on the potential applications of FA-filled composites.
Graphene-reinforced aluminum (Gr-Al) matrix nanocomposites (NCs) have attracted strong interest from both research and industry in high-performance weight-sensitive applications. Due to the vastly ...different bonding characteristics of the Al matrix (metallic) and graphene (in-plane covalent + inter-plane van der Waals), the graphene phase has a general tendency to agglomerate and phase separate in the metal matrix, which is detrimental for the mechanical and chemical properties of the composite. Thus, synthesis of Gr-Al NCs is extremely challenging. This review summarizes the different methods available to synthesize Gr-Al NCs and the resulting properties achieved in these NCs. Understanding the effect of processing parameters on the realized properties opens up the possibility of tailoring the synthesis methods to achieve the desired properties for a given application.
The tribological behavior of graphene and graphite as additives in canola oil was investigated with a pin-on-disk tribometer. The wear surfaces of the aluminum pins lubricated with the ...additive-containing canola oil were analyzed by scanning electron microscopy (SEM). It was found that graphene and graphite as additives in oil show a lower coefficient of friction and wear rate in comparison with neat canola oil. The graphene sheets are more effective than graphite flakes to reduce friction and wear. In addition, there is a proper concentration where the coefficient of friction (COF) and wear are in minimum value. The optimal concentration of the additive in canola oil is about 0.7 wt %. Therefore, the load-carrying capacity and antiwear ability of the lubricating oil are improved. Moreover, the worn surface of aluminum pins is smother in the presence of solid lubricant rather than neat oil.
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