Fiber deformation behavior of discontinuous CFRTP in gear forging

The purpose of the study is to elucidate fiber deformation behavior during the forging of a spur gear by using a carbon fiber reinforced thermoplastic billet. The billet was composed of PA6/UD chips with a fiber length of 30 mm and fiber volume fraction of 50%. A gear forging mold was developed to deform the billet into a gear shape without cutting the fibers. Three types of billets were prepared: a horizontal billet with fibers orientated in the X and the Y directions, a vertical billet with fibers orientated in the Z and the X directions, and a random billet with fibers randomly orientated in the X–Y plane. The fibers along the tooth profile were formed using the horizontal and vertical billets. The adjacent teeth were connected by the fibers. A maximum tooth bending strength was 500 MPa. The delamination occurred under the tooth valley. The orientation of fibers in the teeth using the random billet was also random. The fracture occurred in the middle of the tooth. The results indicated that the fiber orientation in the billet is strongly correlated to the fiber orientation in the gear teeth and the tooth strength. The fiber orientation in the billet proposed in the study can form a tooth with fibers along its profile and with high strength.