Mode I and Mode II interlaminar fracture toughness of glass-cloth/epoxy laminates at cryogenic temperatures

Experiments and analysis on glass-cloth/epoxy laminate double cantilever (DCB) and end-notched flexure (ENF) specimens are presented. The Mode I and Mode II interlaminar fracture tests were conducted by the DCB and ENF test methods, respectively, at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K). The effects of temperature and geometrical variations on the interlaminar fracture toughness are shown graphically. The fracture surfaces were also examined by scanning electron microscopy to verify the fracture mechanisms. A finite element model was further used to perform the delamination crack analysis. Critical load levels, and the geometric and material properties of the test specimens were input data for the analysis which evaluated the Mode I and Mode II energy release rate at onset of delamination crack propagation. The results of the finite element analysis are utilized to supplement the experimental data.