Abstract
The thermo-oxidative stability of toughened unidirectional bismaleimide/carbon fiber composites produced through a layering process was evaluated in isothermal aging experiments in air. By carefully examining different sample size and anisotropic effects with weight loss measurements, degradation rates in the three principal directions were determined; it was found that different degradation mechanisms were operative in different directions. Effective diffusion coefficients and time exponents for three principal directions were determined and utilized to predict the composite degradation rates for various size specimens with different fiber orientations. The developed model equations quantitatively predicted weight loss data, demonstrating the validity of a 3-D anisotropic composite degradation methodology. Finally, the degradation zone was microscopically observed to move into the unreacted 'core' zone as aging time increased, and was found to be significantly dependent on the fiber orientation pertaining to the composite anistropy. Both the theory and experimental results demonstrated conclusively that the thermo-oxidative stability (TOS) of fiber reinforced composites is a tensorial based property (i.e., it depends on magnitude and direction.) although it is traditionally measured through scalar weight loss measurements.
| Original language | English |
|---|---|
| Pages (from-to) | 10-18 |
| Number of pages | 9 |
| Journal | S.A.M.P.E. quarterly |
| Volume | 24 |
| Issue number | 1 |
| State | Published - Oct 1992 |
| Externally published | Yes |