Effect of fiber/matrix interphase on the long term behavior of cross-ply laminates. Ph.D. Thesis
A systematic study was conducted to examine the influence of fiber surface treatment and sizing on the formation of fiber-matrix interphase and its effects on the mechanical properties of composite laminates. Three material systems having the same Apollo graphite fibers and HC 9106-3 toughened epoxy matrix, but with different fiber surface treatments and sizings were used in this study. The fibers used in the 810 A and 820 A systems received 100 percent and 200 percent industry standard surface treatments respectively, and were sized with Bisphenol-A unreacted epoxy material. The 810 O system was manufactured with 100 percent surface treated fiber that were sized with pvp(polyvinylpyrrolidone), a thermoplastic material. The presence of different interphase in these materials was confirmed using a permanganic etching technique. Results indicate that the interphase is discontinuous and made of linear chain polymeric material in the 810 A system. The interphase in the 810 O system has a gradient morphology while the 820 A system does not possess a well defined interphase. Mechanical test results indicate that the 810 O system has a significantly greater longitudinal tensile strength and failure strain compared to the 810 A system. The 810 A and 820 A systems have similar longitudinal tensile properties. Transverse tensile test results indicate that the 820 A system has the highest strength while the 810 O system has the lowest strength. The (0,90(sub 3))-s cross-ply laminates from the three material systems exhibit different damage mechanisms and failure modes under monotonic tensile loading. Fatigue test results indicate that the 810 O laminates have longer fatigue lives at higher load levels and shorter fatigue lives at lower load levels compared to the 810 A laminates. The 820 A laminates have longer life compared to the other two materials systems, at all three load levels. The 810 O material exhibits greater damage and stiffness reduction than the other materials.
- Research Organization:
- Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)
- OSTI ID:
- 237308
- Report Number(s):
- N-96-22738; NIPS-96-09069; TRN: 9622738
- Resource Relation:
- Other Information: TH: Ph.D. Thesis; PBD: Jan 1994
- Country of Publication:
- United States
- Language:
- English
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