Todd A. Bullions

Moisture Sorption Effects on and Properties of a Carbon Fiber-reinforced Phenylethynyl-terminated Poly(etherimide)

This paper reports the results of anin vestigationof moisture sorption effects on the properties of a carbon fiber-reinforced high-performance phenylethynyl-terminated poly(etherimide). Due to the relative newness of this material, minimal information regarding its performance under the duress of environmental effects is known. Composite and neat resin specimens were cycled to effective moisture equilibrium during exposure to a 85% relative humidity/90 C environment followed by exposure to a 10% relative humidity/90 C environment. The composite through-the-thickness moisture diffusion coefficients (Dz) ranged from 2.3 × 10 -6 to 6 mm2/s. The value of Dz for moisture absorptionwas measured to be about 67% greater thanthe value of Dz for moisture desorption; residual stress-accelerated diffusion, void-assisted diffusion, and diffusion hindered by moisture–matrix interactions are discussed as possible explanations for this difference. At 85% relative humidity, the effective moisture equilibrium content of the composite and neat resin were 0.52 ± 0.02% and 1.60 ± 0.01%, respectively. The average transverse moisture expansion coefficient of the composite was 1.1 × 10 -3±0.7 × 10-3. The 1.2% retention (85% 7.0% retention (10% relative humidity) of the control 9.5 MPa. No conclusive results were obtained from open-hole compression strength and apparent interlaminar shear strength tests. The majority of the surfaces of the TFS specimens displayed moisture sorption induced damage. The dramatic impact that inadequate matrix cure can have on a composite’s ability to transverse flexural strength (TFS) specimens exhibited 60.7 ± relative humidity) and 83.6 ± value of 135.9 ± endure a single moisture sorption cycle is illustrated by comparison with a previous moisture exposure study of this material.

Carbon Fiber Reinforced Rigidizable Space Structures

In attempts to provide an active solution for the rigidization of flexible space structures, internal resistive heating is applied to a novel thermosetting resin. Carbon-fiber tow coated in U-Nyte Set 201A, which cures at ∼150°C, was heated by passing electric current through the reinforcing material. Using a proportional-integral (PI) controller, precise temperature control of the heating process was established. Samples cured via controlled internal resistive heating were heated to 160°C and underwent material consolidation in less than 7 minutes. A change in material stiffness was measured to be almost two orders of magnitude greater than that of an uncured material.