Friction & Wear of Composites Materials

For several decades, composite materials have been attracted attention in advanced structural and tribological applications. Friction & Wear of Composites Materials (Ceramic and Polimeric) are presently used in diverse tribological applications such as precision instrument bearings, cutting tools inserts, semiconductors, cilinder liners, seals, automotive cam rollers.

Composites Materials

Ceramic Matrix Composites

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Polymeric Matrix Composites

Ceramic Matrix Composites

Advanced structural ceramics (ceramic matrix composites) have been the focus of research and development in the last two decades for a wide variety of engineering applications owing to its excellent mechanical and thermal properties: high hardness, fracture toughness, compressive strength, stiffness, good wear and corrosion resistance and low thermal conductivity. These materials (structural ceramics) are widely applied in several  tribological applications such as: cutting tools, seal rings, valve seats and in a variety components of high efficiency engines where are required excellent tribological characteristics such as wear resistance and chemical stability at elevated temperatures. Design and selection of ceramics for these applications require reliable data on the effects of temperature, load and environment on the tribological behavior of these materials.                           

In the present work, a-sialon matrix composites reinforced with different amounts of b-Sialon fibers were produced with the aim of improving their toughness to increase the industrial applications. The wear properties of a-sialon matrix composites were evaluated by carried out wear tests using a pin-on-disk tribometer under dry conditions. The a-sialon matrix composites were manufactured by slip casting and sintered by uniaxial hot pressing. Scanning electron microscopy (SEM), and energy dispersion spectroscopy (EDS) were used to analyse the worn surfaces of the a-sialon matrix composites. The results show that the wear of a-sialon matrix composites is caused by adhesion and micro abrasion between the rubbing surfaces and is strongly dependent on the amount of added b-Sialon fibers. Namely, a higher wear rate was obtained as fibers content increased. 

Figure 1 show the evolution of wear rate (Ws) as function of the wt.% of b-sialon fibers

Figure 1- Evolution of wear rate (Ws) as function of wt. % of added b-sialon fibers

Figures 2 shows the morphologies of the worn surfaces of the a-sialon matrix composites with 10- and 30-wt.% of b-sialon fibers, respectively

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Polymeric Matrix Composites

Polyethertetherketone (PEEK) is a high performance, semicrystalline thermoplastic. The good combination of thermo-mechanical properties and relatively low friction and wear with the advantages of easy processability by injection and extrusion renders the potential of PEEK composites for triboaplications a very promising one. The addition of carbon fibres into PEEK has a beneficial effect on its strength and tribological properties.The tribological behaviour of PEEK and its composites have been studied by many researchers and the influence of various experimental parameters, such as load, speed, sliding distance, counterface roughness and test temperature have been reported. Due to the excellent wear and frictional behaviour this material is widely regarded as the highest performance thermoplastic material currently available. PEEK-CF30 exhibit outstanding wear resistance and relatively low friction over wide ranges of pressure, sliding velocity, contact temperature and counterface roughness. These high performance materials are readily processable using a wide range of conventional thermoplastic processing equipment. The exceptional property profile of PEEK-CF30 enables it to be utilized in many of the most critical areas in general industry, such as: automotive, electronics, medical and aerospace.

In this work statistical techniques were used to study the effects of pv factor, temperature and sliding distance on the dry sliding tribological behaviour of 30wt.% carbon-fibre-reinforced polyetheretherketone composite (PEEK-CF30). A plan of experiments, based on the combined techniques using orthogonal arrays and ANOVA, was performed on a pin-on-disc machine PLINT TE67HT^Ò. The obtained results show that friction coefficient was highly influenced by sliding distance factor and, in a smaller degree, by the pv factor. The weight loss was by influenced by the temperature factor and by sliding distance.

Figure 3 - Effect of pv factor; temperature and sliding distance on the PEEK-CF30/steel weight loss

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