Date of Award

2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

Shivakumar, Kunigal

Abstract

The primary limitation of fiber reinforced composite laminates is their poor interlaminar strength and fracture toughness that result in poor impact damage resistance and tolerance. A number of methods have been tried to address this limitation. These methods are limited by factors such as increase in cost, weight, or loss of in-plane properties. A promising approach which does not degrade the in-plane properties is interleaving. Thermoplastic particle interleaving has been applied to reinforce laminates but the primary concern of in-plane properties degradation has not been addressed. Polymer nano-fiber interleaving was investigated in this dissertation as an alternative approach to particle interleaving. The concept showed promise because of the very high surface area to volume ratio and high strain to fracture of the interleaving Nylon-66 nanofibers. The objectives of the work were to determine the relationship between the electric field and the polymer flow-rate, to improve the electrospinning process, to assess low-velocity impact damage resistance and tolerance, and to compare the performance of the base laminate to the interleaved laminate. An electrospinning set-up with a collector current management technique was developed to match the electric field to the flow-rate. Twenty-four ply quasi-isotropic base and interleaved AS4/3501-6 composite laminates were produced. Interleaving was achieved with 0.7 g/m2 nano-fabric. The impacted specimens were retested in compression. The results showed that interleaving increased the threshold impact height and force by 26% and 13%, respectively. At 4.0 J threshold impact energy, residual compression strength was 40% for the base and 45% for the interleaved laminates.

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