Moisture effects on the behavior of graphite/polyimide composites

Autor: R. F. Eduljee, Mark R. Vanlandingham, John W. Gillespie, Loyd J. Burcham
Rok vydání: 1996
Předmět:
Zdroj: Polymer Composites. 17:682-690
ISSN: 1548-0569
0272-8397
Popis: The effect of moisture on the material behavior of Magnamite® IM7 Graphite/Avlmid® K3B thermoplastic polyimide composite laminates has been investigated. Laminates consisting of a 62 vol% fiber were laid up with several different stacking sequences : [90] 10 or unidirectional, [O 2 /90] s or thin cross-ply, [0 2 /90 2 /0 2 ] s or thick cross-ply, [45/0/-45/90] s or quasi-isotropic, and [0/90] laminates. In this study, the glass-transition temperature, T g , and the intralaminar fracture toughness, G Ic , were measured for dry and moisture-saturated unidirectional samples. When laminates were saturated with moisture, the value of T g was found to decrease from its baseline (dry) value, but recovered upon redrying the samples. This observation is consistent with the effects of moisture on the T g of other polymer composites. Permanent toughness losses have not been observed in samples conditioned in room-temperature 75% and 100% relative humidity environments. However, during long-term conditioning of cross-ply and quasi-isotropic samples in liquid water, transverse cracks initiated in the absence of an applied mechanical load. Moisture uptake curves for conditioning in room-temperature liquid water, 80°C (176°F) liquid water, and at room temperature and 75% relative humidity were used to calculate Henry's Law constants and diffusion coefficients. Non-Fickian behavior, consisting of a postsaturation increase in moisture uptake, was observed in cross-ply and quasi-isotropic laminates and might be due to the observed transverse cracking.
Databáze: OpenAIRE
Externí odkaz: