Evaluation of Char Strength of Polymer Nanocomposites for Propulsion Systems

Photo of Andrew Edd, Manuel Jaramillo, Dan M Wells Students: Andrew Edd, Manuel Jaramillo, Dan M Wells

Sponsor: The University of Texas at Austin

Date: Spring 2010

Requirements:
The team must develop a char testing device that is fully automated, highly sensitive to small changes in force, easy to use and capable of running highly repeatable tests. A LabVIEW control program must be developed to run the device and perform the specified protocol and process the data. The constraints on the project consist of a $400 budget and a maximum device weight of 40 lbs.

Problem:
The purpose of this project is to develop a testing protocol and decision criteria with which to compare samples, and to design and build a sensor for determining the char strength of polymer nanocomposites. Polymer nanocomposites are used in solid rocket motors to provide heat protection to key components by the mechanism of ablation. Ablation causes a material to erode over time in a sacrificial manner to provide protection. The current industry standard material for this application is Kevlar®-filled EPDM Rubber, however a newer material, Thermoplastic Polyurethane Nanocomposite Elastomers, or TPUNs, may prove to be the next generation of ablative material, which is what the team's sensor will eventually test.

Solution:
The team chose a design that consists of a vertically mounted linear actuator with a probe attachment to crush the char material and measure the force of destruction required via a piezoresistive load cell. The apparatus is mounted on steel plates to guarantee structural soundness and ensure any vibrations in the structure did not taint the test data. The device is controlled by an intuitive LabVIEW program and a hand-crafted control circuit that guarantees every test runs smoothly and accurately. Unfortunately, the team was unable to run tests on TPUN char samples due to unforeseen destruction of the samples. However, the device is fully functional and ready to be used whenever new samples can be made.

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