THE SHEAR GAUGE - FOR RELIABLE SHEAR MODULUS MEASUREMENTS OF COMPOSITE-MATERIALS

A special strain gage called the 'shear gage' was developed for compos ite materials testing with notched shear specimens. The shear-gage rec ords the average shear strain across the entire test section between t he notches of the losipescu and compact shear specimens rather than ju st sampling the shear strain over a small region in the center of the test section. Hence, the shear stress/strain response is obtained by d ividing the average shear stress (load divided by the cross-sectional area between the notches) by the average shear strain. By placing gage s on both faces of the specimen, accurate and repeatable shear-modulus measurements can be made without prior knowledge of the shear strain or stress distributions. This scheme essentially integrates the shear strain through the entire test section. Knowledge of other material pr operties is not required to accurately determine shear modulus values. The shear gage was tested on a variety of composite and isotropic mat erials resulting in more reliable shear modulus determination and less scatter than previously possible.