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Experimental Investigation of Formability and Mechanical Properties of Composites Manufactured by Direct Roll Bonding

Maleki, Payam | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54707 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Akbarzadeh, Abbas
  7. Abstract:
  8. In this study, the ST14 low carbon steel sheet was used as a skin layer in the construction of three-layer laminates. The use of this steel was due to its high mechanical properties and excellent formability. A thermoplastic polyurethane sheet was also used as the core layer. The selection criteria of this polymer were no need for adhesive (for bonding metal to polymer) as well as proper mechanical properties (elongation and strength) and physical (density). The perfect process for manufacturing three-layer laminates is the roll bonding process. To manufacturing a laminate with the desired properties of the designer, the rolling parameters (rolling speed and thickness reduction) must be controlled. Thermal analysis tests were used to identify the behavior of the polymer under heat. A temperature of 200% was selected as the process temperature (preheating temperature). One surface of the metal specimens was brushed in the rolling direction and cleaned with acetone. Three rolling speeds of 25, 35, and 45 rpm were used to make three-layer laminates in four different thickness reductions (30%, 40%, 50%, and 60%). The thickness of the initial metal and polymer sheets was 0.45 and 2 mm, respectively. The optimum rolling speed after detecting the metal / polymer bond strength by T-Peel and Lap-Shear tests was selected 25 rpm. The reason for this choice was the high shear and normal strength at low rolling speeds due to the longer passage time of the sample between the two rolling rollers. The results of the SEM analysis also supported such a claim. After determining the optimal rolling speed, composite samples were made in four different thicknesses. Evaluation of mechanical properties of samples was performed by uniaxial tensile test. The results showed that with increasing the volume fraction of the polymer, the yield and ultimate tensile strengths decrease. Also, high bond strength laminates showed higher elongation. There was no clear relationship between the work hardening exponent and the volume fraction of the polymer. In order to know the bending and springback behavior of laminates, three-point bending and Hat-shape bending tests were used, respectively. The results showed that with increasing the volume fraction of the polymer, the flexural strength decreases. Also, the initial springback of laminates with high polymer volume fraction is less than thin laminates. However, the delayed springback increased with increasing polymer volume fraction. To evaluate the vibration damping properties, the damping test of a cantilever beam sample was performed. The results showed that with increasing the thickness of the polymer core, due to the role of the polymer in improving damping properties, the amount of damping factor increased, and as a result, the ability of the laminate to absorb vibration increases. The formability of the three-layer samples was investigated by the Nakazima test (hemispherical punch test). The test results showed that with increasing the volume fraction of the polymer, the formability of the laminate increases. Also, the limit dome height test of a sample with biaxial tensile conditions showed that the fracture force of the samples increases with increasing the volume fraction of the polymer. Also, the dome height of the specimens increases with increasing core thickness
  9. Keywords:
  10. Roll Bonding ; Bond Strength ; Mechanical Properties ; Damping ; Formability ; Three Layerd Composite ; Steel/Polyurethane/Steel

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