Mode II Interlaminar Fracture and Damage Evaluation of GFRP Woven Laminates at Cryogenic Temperatures using the 4ENF Specimen

ABSTRACT: This article focuses on understanding the Mode II interlaminar fracture and damage behavior of glass fiber reinforced polymer (GFRP) woven laminates at cryogenic temperatures. A four point bend, end notched flexure (4ENF) test is performed at room temperature (RT), liquid nitrogen temperature (77K) and liquid helium temperature (4K), and an R-curve characterization is conducted for determining the mode II cryogenic fracture properties of GFRP woven laminates. The test configuration is also analyzed by finite element analysis coupled with damage. The damage distributions within the 4ENF specimens are predicted, and the effect of damage on the Mode II energy release rate is examined. This work is the first application of failure criteria (Hoffman criterion and maximum strain criterion) to the description of the R-curve behavior and interlaminar fracture toughness values of woven laminate ENF specimens at cryogenic temperatures. KEY WORDS: cryomechanics, end notched flexure testing, finite element analysis, woven glass–epoxy laminates, fracture toughness, delamination, damage, super-conducting magnets