Stochastic Macro-scale Strength Model for Short Carbon Fiber Reinforced Thermoplastic Materials

Abstract

Short carbon fiber reinforced thermoplastic (SCFRTP) composites are expected to reduce production cost by improving production efficiency and increasing the fuel efficiency of transportation equipment. An SCFRTP material is a composite material fabricated by mixing short carbon fibers of length 0.1–10 mm with thermoplastic resins. It can be easily and rapidly molded by pouring it into molds. However, fiber orientations are randomized owing to the flow of the bulk material during molding. This hinders an accurate evaluation of the mechanical properties of the material, such as strength and rigidity, and a reliable evaluation method remains to be developed. In this study, we aimed to establish a macro-scale strength model that considers the orientation uncertainty of SCFRTP fibers. The modelling approach was verified through micro-scale fracture simulations. High-precision X-ray images were obtained from SCFRTP test specimens to construct mesh models that accurately reproduce the micro-scale structure of the specimens. To examine the influence of orientation uncertainty on material strength, multiple fracture simulations were performed on several subdivided unit-domain models obtained from the original mesh model. The results were statistically investigated. Furthermore, this paper discusses the appropriate modeling techniques for macro-scale fracture simulations.