Fracture mechanics of composites: Reinforcement of short carbon and glass fibers

This chapter deals with fracture mechanics of composites reinforced with short carbon and glass fibers. A short carbon fiber-reinforced polyamide 66 (SCFR-PA66) with 20 wt% fibers is introduced firstly. Then, dynamic fracture properties of the short glass fiber-reinforced polyamide 66 with 30 wt% of fibers (SGFR-PA66) are discussed. The influences of moisture on the fracture behavior of these materials are investigated through experimental studies. The impact properties of specimens are analyzed using a Charpy impact instrument. The fracture tests in the edgewise position of specimens are performed using Standard ISO 179. The results indicated that the moisture greatly affects the dynamic energy release rate of both materials. SGFR-PA66 has a higher dynamic energy release rate than SCFR-PA66. In addition, the dynamic energy release rate of both materials can be achieved at the same value when the moisture exceeds 2.4%. Finally, the fracture mechanism of SCFR-PA66 was investigated and analyzed. The energy release rate GIC of SCFR-PA66 was calculated to determine and predict the fracture properties of the material for the unidirectional short fiber composite.