Effects of Temperature on Microscopic Interlaminar Deformation and Damage in CFRP Cross-Ply Laminates: Application of Micro-Grid/Line Methods

Tensile tests of CFRP symmetric cross-ply laminates were carried out in a SEM (scanning electron microscope), and microscopic interlaminar deformation and damage near a transverse crack tip were visualized by micro-grids or micro-lines printed on the specimen edge surface. The micro-grids or micro-lines were made using photo-lithography technique. The local deformation around the transverse crack tip was observed at 20°C, 80°C, 120°C, and 160°C to evaluate the effect of thermal residual stress on the microscopic deformation and damage in the interlaminar region near transverse crack tips. Temperature dependence of interlaminar shear deformation in the resin rich interlaminar region was clearly demonstrated microscopically for the first time. Temperature dependence of the axial COD (crack opening displacement) was also measured. The displacement field of the specimen edge surface obtained from these experimental results was compared with the mathematical model proposed by Lee and Allen (1989). The theory was modified to consider the temperature effect, and then a good agreement was obtained between the modified theoretical predictions and experimental results.