The role of carbon fibers and silica nanoparticles on friction and wear reduction of an advanced polymer matrix composite

• An advanced composite from carbon fibers and silica nanoparticles was prepared.
• Tribological properties under severe stressing conditions were improved dramatically.
• Different interface structures compared to conventional composites were identified.
• A model on the role of micro/nano-constituents on tribofilm formation is proposed.

Excellent tribological properties of an advanced polymer matrix composite were obtained by a combination of micro- and nano-sized fillers. Surface features and the nanostructure of tribofilms were characterized by advanced microscopic techniques, and correlated with the macroscopic behavior in terms of wear rate and friction evolution. A model based on movable cellular automata was applied for obtaining a better understanding of the sliding behavior of the nanostructured tribofilms. The failure of the conventional composite without silica nanoparticles could be attributed to severe oxidational wear after degradation of an initially formed polymer transfer film. The hybrid composite preserves its antiwear and antifriction properties because flash temperatures at micron-sized carbon fibers, lead to polymer degradation and subsequent release of nanoparticles. It has been shown that the released particles are mixed with other wear products and form stable films at the disk surface thus preventing further severe oxidational wear. Furthermore, the released wear product also is embedding carbon fibers at the composite surface thus preventing fiber fragmentation and subsequent third body abrasion. With nanoscale modeling we were able to show that low friction and wear can be expected if the nanostructured silica films contain at least 10 vol.% of a soft ingredient.

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