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Dissertation
The dynamic mechanical properties of Spectra and Kevlar fiber reinforced composites
Doctor of Philosophy (Ph.D.), Drexel University
1997
DOI:
https://doi.org/10.17918/00008563
Abstract
This thesis describes an effort to characterize the dynamic mechanical properties of Spectra[registered]/Kraton and Kevlar[registered]/epoxy composites based on the characterization of the unidirectional lamina of the same materials. The microstructure of unidirectional lamina (UD) is in between the fiber/matrix level and the composite level. The UD lamina as a 3-dimensional transversely isotropic linearly viscoelastic material was fully characterized. Using the UD lamina as a building block, the viscoelastic behaviors of multidirectional laminates and 3-D braided composites were predicted by modifying and expanding the classical lamination theory and Fabric Geometry Model to include viscoelastic effect, respectively. The time dependent viscoelastic properties of UD lamina of Spectra[registered]/Kraton and Kevlar[registered]/epoxy were determined by combining experimental and micromechanics methods. The high frequency domain properties E11'([omega]) E22'([omega]) and G12'([omega]) were generated by using the Dynamic Mechanical Analyzer (DMA). The DMA results were verified by performing three-point bend and impulse excitation tests. Long time stress relaxation properties of the UD lamina in the time domain were also measured by DMA. The results obtained by the various techniques were shown to correlate well. Poisson's ratio [nu]12([omega]) and [nu]23([omega]) were calculated using the micromechanics model. The Debye equation was selected to recover time domain relaxation moduli function from frequency domain complex moduli by using inverse Fourier Transformation. The full relaxation moduli functions of the evaluated composites which combine high frequency data (transient data) and long time data were obtained. The established viscoelastic constitutive relationship covering a broad time scale was used for the prediction of the viscoelastic properties of several laminates and 3-D braided composite. The prediction has good agreement with the test results. The overall trend agrees with the prediction. It was found that Spectra composites exhibit significant strain rate dependence, resulting in extraordinary high Moduli value comparable with that of diamond in the high strain rate region (13,546 m/s) and much higher than that of the Kevlar composite. The low Tg -70 [degrees]C) of the matrix for Spectra/Kraton composite ensures that the dynamic data obtained at high frequency includes the high damping region.
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Details
- Title
- The dynamic mechanical properties of Spectra and Kevlar fiber reinforced composites
- Creators
- Jenny Zhaoxia Yu
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvi, 204 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021888823104721