Despite composite materials are widely used in many applications, prediction on damage mechanism of the composite materials is still very difficult. Using the findings from the research on damage mechanism under fatigue loading, its transverse cracking and its crack opening and sliding displacement, a mathematical model has been developed. The model showed results closer to the real-time experimental results in crack initiation and growth. The aim of the thesis is to develop a computational tool using the mathematical model and effective stiffness concept of the layers with cracks to predict the degradation of the longitudinal young’s modulus and shear modulus of the composite laminate. In addition to that, graphical user interface is also created making the user control the tool easily. The tool developed shows promising results but still lacks the information on the effects of delamination on crack opening displacement and effective shear modulus.