Theoretical and Experimental Evaluation of Double-Notch Shear Strength of G-10CR Glass-Cloth/Epoxy Laminates at Cryogenic Temperatures

The cryogenic interlaminar shear behavior of G-10CR glass-cloth/epoxy laminates has been discussed through theoretical and experimental characterizations. The use of the double-notch shear test for measuring the interlaminar shear strength of glass-cloth/epoxy laminates at low temperatures is evaluated first. The interlaminar shear tests were carried out with double-notch shear specimens at room temperature, 77 K and 4 K to evaluate the interlaminar shear strength (ILSS) of G-10CR glass-cloth/epoxy laminates. The double-notch shear specimen was loaded on its ends in compression with a supporting jig to prevent buckling. These tests were conducted in accordance with ASTM D3846-79. The effects of temperature, specimen thickness, and notch separation on the apparent ILSS are shown graphically. Fracture surfaces were examined by scanning electron microscopy (SEM) and optical microscopy to verify the failure mechanisms. A three-dimensional finite element analysis was also performed to investigate the effect of specimen thickness and notch separation on the shear stress distribution in the expected fracture plane. Effective elastic moduli were determined under the assumption of uniform strain inside the representative volume element. The numerical findings are then correlated with the representative volume element. The numerical findings are then correlated with the experimental results. The validity of this test technique has been established.