Abstract
The effects of matrix microcracks on elastic moduli of fiber-reinforced plastics (FRP) laminates and their modeling by means of continuum damage mechanics are discussed. The anisotropic damage states in FRP laminates are described by a damage variable of second rank tensor. The damage models, based on the strain equivalence and strain energy equivalence principle respectively, are developed to describe the relations between the damage variable and the elastic moduli of FRP laminates. The two damage models for matrix cracks of lamina are first formulated. Then, these models are extended to the damage models for laminates by making use of classical laminate theory. Finally, the proposed models are applied to predict the change in elastic moduli induced by matrix microcracks for [±45°]s and [0, 90°]s laminates. Comparison with the experimental results available shows that both of the suggested models can reasonably describe the anisotropic effects of matrix microcracks on elastic moduli of FRP laminates. In case of GFRP laminates under uniaxial tension, the model based on strain energy equivalent principle is shown to give some better description of the damage influence than that based on strain equivalent principle.
