Date of Award

8-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Committee Member

Dr. Oliver Myers, Co-Committee Chair

Committee Member

Dr. Garrett Pataky, Co-Committee Chair

Committee Member

Dr. John Saylor

Abstract

In recent years, laminated carbon fiber reinforced polymer (CFRP) composites have gained popularity in engineering applications due to their lightweight and strong mechanical properties. One of this material's greatest weaknesses is that it performs poorly in out-of-plane impact resistance. Thus, it was the objective of this research to investigate the effect of bistability on the impact resistance of laminated CFRP composites. Bistable composites have the ability to alternate between two different geometric equilibria through external loading, and when unloaded, do not require external forces to maintain either geometry. An instrumented dropweight tower was designed and constructed according to ASTM standards with modifications to accommodate bistability. Laminated CFRP composite specimens of bistable, flat monostable, and curved monostable configurations were subjected to low velocity impacts of 20 J. The acceleration and force of each impact was recorded using an accelerometer and a load cell mounted on the dropweight tower's impactor. The sensor data was used to analyze the dynamic response and calculate the energy absorption of each impact. Post-impact crack length measurements and damage characterization were used to conduct a damage resistance analysis. The effects of moisture, geometry, stacking sequence, and bistability of the impacted specimens were determined. The results showed that bistability improves the low velocity impact damage resistance of laminated CFRP composites through increased energy absorption and specimen kinetic energy.

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