Experimental investigation of interlaminar mechanical properties on carbon fiber stitched CFRP laminates

Abstract

Experimental investigations of interlaminar mechanical properties for carbon fiber rein-forced plastic (CFRP) laminates were carried out using aramid fiber (Kevlar®-29 1000d) and carbon fiber (TR40-1K 612d, Mitsubishi Rayon) stitching. Various carbon fiber (CF) stitch densities were used to prepare a number of CF stitched CFRP laminates for double cantilever beam (DCB) tests. An insert tongue-type loading fixture, developed by the Japan Aerospace Exploration Agency (formerly the National Aerospace Laboratory of Japan), was also employed in the DCB test. Interlaminar tension tests were carried out under an out-of-plane directional loading using a single CF stitch thread in the CFRP laminates. The DCB test results clarified that the relationship between the volume fractions of the CF stitch thread (V ft) and mode I critical energy release rate (G Ic) showed a mostly linear function with a higher gradient than that of the Kevlar® stitched CFRP laminates. The CF stitched CFRP tension test results indicated that the consumption energy per unit area (Ei ) was larger than that of Kevlar® stitched CFRP laminates.