Why a cyanate ester composite part blistered: Material characterization and analyses

This paper emphasizes the role and use of various material characterization techniques as problem-solving tools to diagnose and identify the source of the blistering phenomena in a cyanate ester - based part. A cyanate ester based skin/syntactic foam part developed extensive blisters throughout the inner and outer surfaces during a free standing postcure. The result was scrapping of the entire part. The composite layup was a complex stack of skin and cores, three-dimensionally shaped and cured in an outer contour matched tool. Several hypotheses as to why the laminate part blistered were investigated. Analyses included X-ray, photoelectron spectroscopy (XPS), gas chromatography/mass spectrometry (GC/MS) Fourier Transform InfraRed (FTIR) thermomechanical analysis (TMA), and dynamic scanning calorimetery (DSC) techniques. Several experiments were conducted to understand the cause and mechanism of the the blistering phenomena. The cause was found to be a moisture evolution from the glass microballoons contained in the foam layers, We found that moisture from the glass microballoons reacted with the cyanate ester resin to cause an intermediary material that outgassed as carbon-dioxide when internal temperatures exceeded 400 degrees F. The CO2 thus caused the blisters.