Fundamental Research on the Impact Damages and the Evaluation of Residual Strength of Fiber Reinforced Laminated Plates

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Laminated structures of the carbon fiber reinforced plastics (CFRP) are widely used as structural members of the moving bodies such as rotors of the turbine, the fuselage of the air plane and the space structure. one of the major problem of these structures is the foreign object damage (FOD) and the residual strength of the damaged parts.In this research, the impact damages of CFRP laminated plates by the uni-directional prepreg are studied. The CFRP flat plates are impacted normally by the hard and the soft impactors with low velocities. The features of the impact damages and the fatigue residual strength of the damaged specimen are investigated.Main results of this research are summarized as follows :1. For the collision of the hard and the soft impactors to CFRP laminates, the features of the damaged patterns became clear from the observations with the ultrasonic microscope, the optical microscope and the scanning electronic microscope.2. The total area of the delanination is proportional to the impact energy.3. The experimental method to obtain the dynamic load-deflection curve for the laminated plates is developed. Then, the absorbed energies of the laminates were evaluated quantitatively.4. For the three point bending and the four point bending fatigue tests of damaged specimens, it is shown that there is a significant difference to the mechanism of the propagations of the damages.5. Analytical methods of the impact responses for laminated plates are developed in cases of the anisotropic plate theory and the anisotropic three dimensional theory. These methods would be utilized to clear the mechanism of the impact damages of laminates.