Fretting behaviors of interface between CFRP and coated titanium alloy in composite interference-fit joints under service condition

This paper describes an experimental study on the fretting behaviors and tribological mechanism of interface between carbon fiber reinforced polymer (CFRP) composites and titanium alloy in composite interference-fit joints under service condition. A ball-on-flat configuration was employed in the fretting tests where the effect of fiber orientation, ambient temperature, surface treatment and interface condition were evaluated. The coefficients of friction (COFs), 3D surface morphologies and microstructures of worn scars were presented to characterize corresponding fretting mechanisms. An obvious tribological anisotropy was observed in the CFRP specimens where the longitudinal surface possessed much smaller COFs and less wear damage than the normal surface. The wear damage and anisotropic properties can be reduced to a certain extent by surface treatment through improving wear resistance or serving as solid lubricant respectively. The fretting behaviors also show strong temperature dependence. The increasing temperature exaggerates deformation in longitudinal surface and aggravates abrasion in normal surface by softening matrix resin. Wet service condition contributes to reducing COF and wear owing to the formation of a tribofilm on the interface.