Development of an Apparatus for Measuring the Shear Strength of Charred Ablatives

Photo of Ryan Alter, Stephanie Clatanoff, David Forinash (Team Leader), and James Everett Newman Students: Ryan Alter, Stephanie Clatanoff, David Forinash (Team Leader), and James Everett Newman

Sponsor: The University of Texas at Austin

Date: Spring 2012

Requirements:
The device must secure the 12.5 mm x 12.5mm x 50 mm char specimen and accurately measure its shear strength. The data acquisition system must be implemented using LabVIEW. Additionally, the overall dimensions and weight of the tester must be minimized to fit on a laboratory table and be easily moved by one person.

Problem:
An insulation layer in a solid rocket motor protects the outer components from the extreme heat when the propellant is ignited. Effective insulation material must retain enough strength after being charred by combustion to resist the frictional shear forces of the high temperature fluids. The project focused on the design of a system to accurately measure the shear strength of char.

Solution:
Our final design has five major components: the U-Block, the L-Support, Shear Block, actuator, and sensor. The U-Block and L-Support fit together to clamp the char sample tightly in the direction of the shear test while greatly restraining its movement in the lateral direction and allowing for adjustable height. The Shear Block connects to the actuator and transmits the force from the actuator through the sensor, shearing the char specimen. The actuator supports allow the actuator to be raised, leveled, and secured at the height of the char samples. All components are locked in place on a flat surface for testing.

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