Rheological characterization and analysis of a bismaleimide matrix

Abstract

AbstractBismaleimide resins are becoming increasingly attractive as matrix materials for high‐temperature applications in continuous fiber reinforced composites. Their relative low viscosity as well as the low processing temperature makes them attractive candidates as matrices in high‐temperature applications while retaining the processing ease associated with epoxies. Traditional prepregging as well as autoclaving processes, especially for solvent free (hot melt) systems, are a viable way to proceed. However, the recent interest in toughened matrices makes these processing techniques difficult to specify and control. Specifically, during prepregging and autoclaving, the viscosity of the system must be specified from the initial stages of resin mixing through B‐staging and gelation all the way to the viscoelastic “solid” region. In this work, based on a series of well‐characterized bismaleimide resins, a generalized model for viscosity capable of describing matrix changes as it goes through the processing steps was developed. Measurements of viscosity by the different techniques were related through the model to provide a characterization scheme that may be applicable to both prepregging and lamination steps.