Measurement and evaluation of fiber bundle surface of long fiber reinforced woven composites

Abstract

Long fiber reinforced woven composites (LFRWCs) are being applied to many growing fields because of their excellent properties; however, owing to their anisotropy and inhomogeneity, traditional surface measurements and evaluation methods appropriate for isotropic materials are no longer suitable to LFRWC, thus causing many difficulties in terms of their wide industrial applications. Based on this fact, a multi-scale surface evaluation system is proposed according to the LFRWC structure. This paper is mainly focused on the first scale evaluation-fiber bundle scale. First, the reasons why 2D rather than 3D measurements and evaluations should be adopted at this scale are described, and four indexes, namely, Raave, Rqave, Rskave and Rkuave are proposed to evaluate the surface roughness, damage type, and degree of damage. A method is proposed to determine the maximum sampling step (MaxSS) to ensure that the measurement data are undistorted. As a demonstration, the validity of the method is checked through the testing of a carbon fiber reinforced silicon carbide ceramic matrix composite (Cf/SiC).