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Brake pads are vital parts of automobiles, where tribological properties are prime concern. Usually, asbestos brake pads were used, which were replaced by copper-based in later years. As brake lining materials have evolved, synthetic friction composites were explored as alternatives. Recent works suggest that, natural composites are promising friction material. However, poor thermal conductivity and frictional stability have limited their applications. Surface treatment of fibers and addition of secondary fillers have improved their possibilities. Thus, hybridization of reinforcements has expanded their range of applications. The present article attempts to review various aspects of brake pads and their testing with attention on natural composites. Their properties were studied to conform their ability to meet desired requirements. The article reviews the studies conducted in recent years on various materials properties related to brake pads. The future potential of natural components in the development of friction composite materials for automotive applications is highlighted. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to investigate the wear behaviors of aged metal matrix composites and of the as-cast Al-Si alloy by using a pin-on-disk wear testing machine at room temperature.Design/methodology/approach Hypoeutectic (Al-7Si) alloy reinforced with low volume fractions of SiC particles (SiCp) and graphite (Gr) particles were prepared by the stir-casting process. It was found that the addition of 9 Wt.% of SiCp and 3 Wt.% of Gr particles conferred a beneficial effect in reducing the wear rate of the composites.Findings The worn-out surfaces of the specimens were examined using scanning electron microscopy (SEM); the extensive micro cracking occurs on the surface of the Al-7Si alloy tested at lower loads. The growth of these microcracks finally led to the delamination of the base alloy surface. The reinforcements (SiCp and Gr) particles tended to reduce the extent of plastic deformation in the surface layer, thereby reducing extensively the occurrence of micro cracking in the composites.Originality/value From the results, it is revealed that the quantity of wear rate was less for aged specimens compared to the as-cast specimens. The worn-out surfaces were studied using electron dispersive spectroscopy, and wear debris was analyzed using SEM. [ABSTRACT FROM AUTHOR]

In the current investigation, the dry sliding wear characteristics of cenosphere/epoxy composites have been studied under ambient conditions. The sliding wear analysis has been performed on wear rate, specific wear rate and coefficient of friction considering four parameters, namely, sliding velocity, normal load, sliding distance and % filler content. The wear trials were conducted as per full factorial design (FFD) and wear behavior was analyzed through modeling based on artificial neural network (ANN). Proposed models were further employed with differential evolution (DE) optimization to determine the best combination parameters like sliding velocity, normal load and sliding distance for a specified reinforcement, which results in minimal wear. [ABSTRACT FROM AUTHOR]

Purpose – The aim of the this study is to develop a new class of composites which would be more commercially viable and environmentally sustainable via reduced resource depletion, as there has been global interest in utilization of natural resources. The dry sliding wear behavior of glass-epoxy (G-E)-based composites filled with tamarind kernel powder (TKP) in different volume fractions of fillers (0 per cent, 3 per cent and 6 per cent) was studied as per standards. Design/methodology/approach – In the present study, the analysis and optimization of the wear process has been studied. The Taguchi approach to experimental design was used to identify the effect of wear parameters such as applied load, sliding velocity and sliding distance. Taguchi tools such as analysis of variance and multiple linear regression models have been used to analyze, obtain the significant parameters and evaluate the optimum combination levels of wear process parameters. The results of Taguchi analysis indicate that sliding distance was found to be the prominent parameter affecting wear volume loss compared to other wear parameters. Findings – The G-E composites with 3 and 6 vol.% of TKP had the lowest wear volume loss. Multiple linear regression models for all the tested composites’ results well match with experimental results. Confirmation tests were conducted to validate the analysis. There was a close relationship between the experimental results and the statistical model. Originality/value – However, to the best of author’s knowledge, these literature reports related to natural organic filler materials are limited to analysis of polymer matrix composite. Further, the addition of TKP particle as a potential filler has not been addressed. An attempt has been made to clarify the technical viability of TKP as a potential filler for G-E composite. [ABSTRACT FROM AUTHOR]

An attempt has been made to study the influence of wear parameters like applied load, sliding speed, sliding distance on the dry sliding wear of polytetrafluroethylene (PTFE), PTFE + 25% glass and PTFE + 40% bronze composites. Experiments, based on the techniques of Taguchi, were performed to acquire data in a controlled way. An orthogonal array and the analysis of variance were employed to investigate the influence of process parameters on the wear of composites. The worn surfaces were examined using scanning electron microscope (SEM). The experimental results show that sliding distance and applied load were found to be the more significant factors among the other control factors on wear. The objective is to establish a correlation between dry sliding wear of composites and wear parameters. These correlations were obtained by multiple regressions. A good agreement between the predicted and actual wear resistance was seen. [ABSTRACT FROM AUTHOR]

Abstract: The dry sliding wear characteristics of a glass–epoxy (G–E) composite, filled with both silicon carbide (SiCp) and graphite (Gr), were studied using a pin-on-disc test apparatus. The specific wear rate was determined as a function of sliding velocity, applied load and sliding distance. The laminates were fabricated by the hand lay-up technique. The volume percentage of filler materials in the composite was varied, silicon carbide was varied from 5 to 10% whereas graphite was kept constant at 5%. The excellent wear resistance was obtained with glass–epoxy containing fillers. The transfer film formed on the counter surface was confirmed to be effective in improving the wear characteristics of filled G–E composites. The influence of applied load is more on specific wear rate compared to the other two wear parameters. The worn surfaces of composites were examined with scanning electron microscopy (SEM) to investigate the probable wear mechanisms. It was found that in the early stage of wear, the fillers contribution is significant. The process of transfer film, debris formation and fiber breakage accounts for the wear at much later stages. [Copyright &y& Elsevier]

The glass epoxy polymer composites are extensively used for a wide variety of applications in aerospace, automotive, and chemical industries due to an excellent property profile. Even though these composites are produced as near net shapes, the machining has to be performed in the final stage of production. Drilling is one of the most common machining processes used to install the fasteners for assembly of laminates. However, the drilling of these composites is rather a difficult task due to the highly abrasive nature of reinforcement and hence there is a need to study the machining performance. An attempt has been made in this article to investigate the effects of spindle speed and feed on machinability aspects, namely, thrust force, hole surface roughness, and specific cutting coefficient during drilling of glass epoxy composites. The drilling experiments were performed as per full factorial design for both glass epoxy composites and silicon carbide-filled glass epoxy composite materials. The response surface methodology based mathematical models were developed for analyzing the effects of cutting conditions on machinability characteristics. The parametric analysis reveals that the silicon carbide-filled glass epoxy composite material provides better machinability compared to glass epoxy composite without the addition of filler. [ABSTRACT FROM PUBLISHER]

In this work the moisture absorption capability, compressive properties, collapse modes of various types of composite sandwich structures are reported. The tested sandwich structures were constructed with varieties of hybridized skin materials and different compositions of the core materials. The moisture absorption, Flatwise compression and Edgewise compression tests are conducted for core as well as sandwich structures. Comparisons of results have been between the hybridized and non-hybridized sandwich structures. Two modes of collapse were noticed in the Edgewise compressive test, one of which being progressive end-crushing of the sandwich structure featured by significant crash energy absorption. This feature was highly desired for the parts of transportation vehicles. Microscopic analysis has been carried out to know the nature of failure under compressive loads. It has been observed that with increasing the debonding strength of the core–face interface, the failure mode changes from unstable collapse mode stable progressive crushing. [ABSTRACT FROM PUBLISHER]

This experimental investigation deals with the evaluation of abrasive wear behavior of Glass Epoxy (G-E) composites on pin-on-disc test rig. A plan of experiments, based on the Taguchi Design of Experiments, was performed to acquire data in controlled way. An orthogonal array and the analysis of variance were employed to investigate the percentage of contribution of various process parameters like sliding speed, applied load, sliding distance and their interactions affecting the abrasive wear volume loss of composites. The correlations between the various factors affecting the abrasive wear behavior of composites were obtained by using multiple linear regression equations. The obtained results indicate that applied load and sliding distance were the wear factors that have the highest physical as well as statistical influence on the abrasive wear behavior of both filled and unfilled G-E composites. A good agreement between the predicted and actual wear resistance was observed within ± 12%. [ABSTRACT FROM AUTHOR]

The mechanism of translaminar failure in hybrid polymer matrix composites is a typical combination of tensile and bending loads. Experimentations have been carried out on pin loaded single edge notched tensile specimen. The results of the experimental analysis carried out on the influence of failure zone and environmental conditions on the stress intensity factor in glass/ textile fabric (GF/TF) polymer hybrid composites have been reported. The results have shown that the failure zone varies with the fabric volume, the initial crack size and the environment. The results have shown that the acidic environment has maximum influence on the failure pattern and the critical stress intensity factors. [ABSTRACT FROM AUTHOR]

This paper presents the influence of cutting parameters on thrust force, surface finish, and burr formation in drilling Al2219/15SiCp and Al2219/15SiCp-3Gr composites. The composites were fabricated using the liquid metallurgy method. The tools used were commercially available carbide and coated carbide drills. The results revealed that feed rate had a major influence on thrust force, surface roughness, and exit burr formation. Graphitic composites exhibit lesser thrust force, burr height, and higher surface roughness when compared to the other material. The reduced thrust force and burr height is attributed to the solid lubricating property of the graphite particles. The higher surface roughness value for Al2219/15SiCp-3Gr composite is due to the pullout of graphite from the surface. The chips formed when machining graphitic composites are more discontinuous when compared to SiCp reinforced composites and hence advantageous. [ABSTRACT FROM AUTHOR]

Abstract: Aluminium metal matrix composites reinforced with SiC and graphite (Gr) particles was prepared by liquid metallurgy route. Dry sliding wear behaviour of the composite was tested and compared with Al/SiCp composite. A plan of experiments based on Taguchi technique was used to acquire the data in a controlled way. An orthogonal array and analysis of variance was employed to investigate the influence of wear parameters like as normal load, sliding speed and sliding distance on dry sliding wear of the composites. The objective was to investigate which design parameter significantly affects the dry sliding wear. It shows that graphite particles are effective agents in increasing dry sliding wear resistance of Al/SiCp composite. [Copyright &y& Elsevier]