Influence of heating time of pyrolysis method for extracting recycled carbon fibers from wasted Prepreg on fiber breakages in its injection molded composite

The purpose of our study is to investigate the influence of fiber breakages of recycled carbon fibers at pelletizing on a tensile strength of its composite. The recycled carbon fibers used in this study were obtained by extracting from a wasted Prepreg by pyrolysis method in a muffle furnace under air condition at 600 deg-C for 30, 60 and 90min, respectively. Recycled carbon fibers were compounded with PP resin by twin extruder machine where the conditions of the barrel temperature and screw rotation were changed, respectively. A specific mechanical energy for extruding unit mass of compound was introduced, in order to discuss the changes of residual fiber lengths in pellets. It was confirmed that the tensile strength was decreased since flaws on the carbon fiber were induced due to the oxidization process.The measured data of residual mean fiber length in pellets were expressed by a single master curve after the experimental data were shifted according to the SME. The shift factor on the SME was driven by relating with a probability of fiber breakage when the strength of carbon fiber was changed. The other master curve was applied to predict the strength of molded composite where a mechanical model proposed for calculating the strength of composites with chopped fibers was referred. The estimated strengths in this study well agreed with experimental data. It was possible to estimate of the change of tensile strengths of recycled carbon fibers reinforced composites accompanying with the change of strengths of single fibers at recycling process.