Title page for ETD etd-92098-221727


Type of Document Dissertation
Author Gardner, Slade Havelock II
Author's Email Address anon248@vt.edu
URN etd-92098-221727
Title An Investigation of the Structure-Property Relationships for High Performance Thermoplastic Matrix, Carbon Fiber Composites with a Tailored Polyimide Interphase
Degree PhD
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Lesko, John Jack
Marand, Eva
Reifsnider, Kenneth L.
Riffle, Judy S.
Wilkes, Garth L.
Davis, Richey M. Committee Chair
Keywords
  • polyamic acid
  • polyimide
  • interphase
  • composite
Date of Defense 1998-08-17
Availability unrestricted
Abstract
The aqueous suspension prepregging technique was used to fabricate PEEK and PPS matrix composites with polyimide interphases of tailored properties. The structure-property relationships of Ultem-type polyimide and BisP-BTDA polyimide which were made from various water soluble polyamic acid salts were studied. The molecular weight of the polyimides was shown to be dependant upon the selection of the base used for making the polyamic acid salt. The development of an Ultem-type polyimide with controlled molecular weight and properties similar to commercial Ultem 1000 was accomplished with the Ultem-type TPA+ polyamic acid salt. Both the Ultem-type polyimides and the BisP-BTDA polyimides derived from the NH4+ salt and the TMA+ salt were shown to crosslink at elevated temperatures.

Blends of Ultem-type polyimide with PEEK and BisP-BTDA polyimide with PEEK were prepared to study the structure-property relationships of model composite matrices. Since both polyimides are miscible with PEEK, interdiffusion of the polyimides with PEEK is expected, however, the interdiffusion behavior is complicated by the crosslinking mechanism of the polyimides.

Ultem-type polyimide interphase, PEEK matrix composites and BisP-BTDA polyimide interphase, PEEK matrix composites were fabricated using the aqueous suspension prepregging technique and evaluated to determine the effects of the interphase properties on the bulk composite performance and durability. Three different Ultem-type polyimides from the NH4+, TMA+ and TPA+ polyamic acid salts were used and two different BisP-BTDA polyimides from the NH4+ and TMA+ polyamic acid salts were used. The transverse flexure strength was used to qualitatively rank the composites by level of interfacial shear strength. The longitudinal tensile strength of the composites was shown to vary with relative interfacial shear strength. The trend of these data qualitatively support the existence of a maximum longitudinal tensile strength at an optimum interfacial shear strength. Notched fatigue testing of the Ultem-type polyimide interphase, PEEK matrix composites showed that the initial split growth rate increased with decreasing relative interfacial shear strength.

Ultem-type polyimide interphase, PPS matrix composites were fabricated using the aqueous suspension prepregging technique and evaluated to determine the effects of the interphase properties on the bulk composite performance. Three different Ultem-type polyimides from the NH4+, TMA+ and TPA+ polyamic acid salts were used. The transverse flexure strength was used to qualitatively rank the composites by level of interfacial shear strength. The longitudinal tensile strength of the composites was shown to vary with relative interfacial shear strength. The trend of these data qualitatively support the existence of a maximum longitudinal tensile strength at an optimum interfacial shear strength.

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