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Numerical and Experimental Analysis of Composite and Honeycomb Sandwich Panels Fatigue Behavior

Khodabakhshi, Mohammad Erfan | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55114 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Sayyadi, Hassan
  7. Abstract:
  8. The use of sandwich panels has become very common in recent engineering designs when the weight of the part or structure is important and we are looking to lose weight while maintaining strength. The mechanical properties of this type of structures, including yield stress, fatigue behavior and estimation of their life, failure modes, natural frequencies and resonance phenomena, etc. are affected by various factors, including geometric and environmental factors. Fatigue is one of the most common failures in these structures. Composite materials have complex structures. In these materials, due to the viscoelastic properties, the fatigue behavior changes with changing stress, stress frequency, temperature or different amounts of stress. Other complexities of these materials include failure modes and their multiaxial stress modes. The stress distribution in a composite material is often multiaxial, even if subjected to a single load. Therefore, accurate knowledge of the behavior of sandwich panels with different cores in loading fatigue in order to design reliable structures is of particular importance. In this study, the effect of geometric factors, loading frequency and the effect of initial crack position on the fatigue life of composite sandwich beams and honeycomb beams and their failure modes have been investigated. The research consists of two parts of numerical analysis with finite element software and experimental experiments in which the samples are subjected to three-point bending test. Experimental samples are of two different types. The first group of samples has XPS foam core and fiberglass as a sandwich panel cover, and the second group has NOMEX honeycomb core. For each example, displacement-cycle diagrams, force-cycle diagrams, stress and displacement contours, and the dominant failure state in the problem are presented. Comparing the results obtained in experimental and numerical experiments, it was found that by reducing the beam width, there was a significant effect on the final life of the samples and reduced the life of the samples. By increasing the loading frequency, the samples failed much earlier under the same loading, and with the departure of the initial crack from the center of the beam, the life of the samples increased.
  9. Keywords:
  10. Sandwich Panel ; Castled Beam ; Fatigue ; Three Point Bending Test ; Finite Element Method ; Laminated Composite Beam

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