FRACTAL PROPERTY OF MATRIX CRACKING IN GFRP CROSS-PLY LAMINATES

Matrix cracking is the most important damage mechanism in FRP structur es because it causes stiffness degradation of structures and becomes t he origin of delaminations. In this study, therefore, with specimens o f stacking sequence [0/90(4)](s), tension tests were conducted and in situ observations of the matrix cracking in the 90 degrees pig's were made by a replica method. As a result, the distribution of the matrix crack positions was experimentally proven to be a fractal distribution of D=0.45 and was constant at any loading levels. Using this fractal distribution, the stiffness degradation was evaluated based on an imag inary crack density. Based on these results, the fractal distribution of the initial defect size was modeled and experimentally proven to be a fractal distribution of D=1.6. The model was applied successfully t o predict variations of crack density with increasing applied load usi ng damage mechanics.