Alternate Test Methods for Graphite Epoxy Mechanical Properties

Authors: Michael J. Viens, Goddard Space Flight Center

Abstract

The work performed for this memorandum investigated the use of three devices which could potentially reduce both cost and turn around time for testing graphite epoxy (Gr/Ep) tensile coupons. Gr/Ep test coupons are typically tabbed to facilitate load transfer to the test coupon and are strain gauged to determine stiffness and strain at failure of the test coupon. The implementation of the aforementioned devices would eliminate the need for both test tabs and the strin gauges. The tensile loading of tabless coupons was performed using hydraulic grips with hybrid wedge surfaces to transfer load the test coupons. The strain in the test coupons was monitored using a laser extensometer. The coupon stifness was measured prior to tensil testing with a sonic resonance measurement system. This memorandum reports the results of these tests and compares the strength results to that of previous tests and the strain results obtained using strain gauges.