Abstract
The lateral deformation properties of oriented polymer fibres were examined by transverse compressive and torsional experiments. A modified interfacial test system machine was used to study the transverse compressive deformation behaviour of thermally cross-linkable poly (p-1,2-dihydrocyclobutaphenylene terephthalamide) (PPXTA) fibres and of a number of commercially available polymers (Nomex, nylon, Kevlar, Dacron) and ceramic (Nicalon and FP) fibres. The torsional (shear) modulus G of PPXTA and Kevlar poly (p-phenylene terephthalamide) (PPTA) fibres was measured by pendulum experiments. During both fibre torsion and transverse compression, the deformation involves materials slip on (h k O) planes, in the [001] direction for the torsion and the [h k O] directions for transverse compression. The intermolecular crosslinks in PPXTA did not significantly modify the elastic transverse modulus Et and caused only slight (13%) increase in shear modulus G. However, the plastic transverse properties of cross-linked PPXTA were significantly different than those of uncross-linked PPXTA. The stress at the proportional limit σ̄p, determined from the transverse load displacement curves, was substantially higher for the cross-linked fibres than for the uncross-linked fibres. In addition, the cross-linked PPXTA fibres exhibited a large strain recoverable response reminiscent of elastomers, whereas the PPTA and uncross-linked PPXTA fibres exhibited a large strain irreversible response.
| Original language | English |
|---|---|
| Pages (from-to) | 2855-2871 |
| Number of pages | 17 |
| Journal | Journal of Materials Science |
| Volume | 32 |
| Issue number | 11 |
| DOIs | |
| State | Published - 1997 |
Funding
This research was supported by the US Army Advanced Concept Technology Committee (DAAK6-92- K-0005). Generous support was also provided from DuPont, Hoechst-Celanese, and the NSF National Young Investigator Program (NSF-DMR-9257560). The authors acknowledge Steve Allen and Warren Knoff for helpful discussions, Robert Irwin for spinning our polymer, and the High Temperature Material Laboratory of Oak Ridge National Laboratories for providing the interfacial test system machine. The use of the interfacial test system at Oak Ridge National Laboratory was possible thanks to the support from the US Department of Energy, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Industrial Technologies, Industrial Energy Efficiency Division and Continuous Fibre Ceramic Composites Program and by the US Department of Energy, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Transportation Technologies as Part of the High Temperature Materials Laboratory User Program under contract DE-AC05-96OR22464 with Lockheed Martin Energy Research Corporation. MCGJ also thanks Wright Patterson Air Force Base for the use of their flat-film X-ray camera.