Date of Award

12-2008

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Biggers, Sherrill B

Committee Member

Kennedy , John M

Committee Member

Law , E. Harry

Abstract

An energy dissipation system is proposed for use on consumer passenger automotive vehicles and auto racing stock cars. This system will be utilized to protect the occupants from frontal impacts with stationary or near stationary objects. The system will be affixed to the front of the car's primary structure. It is proposed to replace the traditional steel bumper currently in use. This system will not increase the weight of the car, nor will it adversely affect the aerodynamics of the body. The system will improve the crashworthiness of the vehicle. Advanced composites will be the primary sacrificial element in the system. Carbon fiber composites are proposed for constructing the system and as the sacrificial element in the system. The system will employ a set of ripping blades to dissipate the energy from an impact and control the deceleration of the vehicle and occupant. A more detailed design explanation can be found in Appendix B. However, the system may be constructed of both steel and composites. The use of composites for the system should significantly lighten the front end of the car and allow greater flexibility in the weight distribution of the vehicle. The proposed system will also be easily modified for different platforms or race conditions and easily replaced in the event of an impact.
Previously, composites have been examined for a similar application. The most prevalent of these designs was the 'Humpy bumper,' which was composed of multiple layers of carbon fiber which were crushed, and/or delaminated during impact. While this design was prototyped and tested, it was never placed in production. Possibly, one of the largest flaws in the design was that it could only be used once and that the front of the vehicle roll cage might need large modifications.
This thesis will examine the mechanism using ABAQUS to create an accurate model of the material behavior to aid in the design and fine tuning of the ripped assembly before prototyping. This is important because it not only decreases design costs but also the time to market release for the mechanism.
In order to obtain an accurate model, material types and other design variables were investigated. Various material orientations and stacking sequences were explored. Multiple ripper blade profiles were also tested. It was determined that a round ripper blade with a
[+60/-60]2S stacking sequence produced the best combination of smooth response with low force.

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