Quality analysis of prepreg tow for automated fiber placement and its influencing factors

In recent years, with the rapid development and application of automated fiber placement (AFP), the demand for prepreg tow has increased considerably. However, no consensus has been achieved on the evaluation system including the analysis method of the quality of prepreg tows in domestic. In this paper, the quality of prepreg slitting tows had been comprehensively analyzed by systematic methods. It was found that the slitting qualities of the domestic prepreg tows, including the width uniformity, the paralleling degree of fibers at the joint and the fiber fracture at the edge were all well controlled by using image and weight analysis. Effect of preparation methods, namely discontinuous hot-press process and continuous rolling process, on the quality of tow joint was investi-gated through the tensile-shear strength and peeling force testing. The results show that the process temperature and the time of duration are the key factors. In contrast, the joints made by continuous rolling process have more stable mechanical properties than those prepared by hot-press process. Meanwhile, the joint performance is impacted by the environmental conditions, wherein the humidity has more significant influence than the test temperature. With the prolongation of storage at room temperature, the mechanical properties of the joints first increased and then decreased. The DSC and IR characterization indicates that the property changes relate closely to chemical reactions and increasing curing degree of the resin matrix at the interface. The fatigue performance of the joint was tested by repeated roller passing and subsequent damage analysis. It reveals that the tensile-shear strengths of the fatigued joints decrease with increasing roller temperature, higher tension and more turns.