Dielectric properties and degradation monitoring in polymer-matrix structural composites

Abstract

The degradation of a thermally-aged bismaleimide-glass fiber composite system was assessed via spectroscopic methods. Composite samples were subjected to accelerated isothermal aging at temperatures (275, 300, 325, 350 and 375 • C) near or above the upper usage limit of 290 • C. Broadband dielectric spectroscopy was used to measure changes in the dielectric spectra of aged composites from 200 Hz to 2 MHz, while chemical changes in the resin were identified with Fourier transform infrared photoacoustic spectroscopy. Additionally, samples were mechanically assessed via a double-notch compression test. Relationships between the dielectric, photoacoustic, and mechanical properties are inferred from the results.