Effect of damage on the impact response of composite laminates

The effect that the presence of damage has on the impact response of composite laminates was studied. The impact response was segmented into two phenomena: local contact response and structural response. These phenomena were characterized by conducting static indentation tests and impact tests, respectively. Tests were conducted on [+45/0]2~ graphitelepoxy laminates with and without predamage. The force versus indentation results were compared for the local response and the force and displacement versus time histories were compared for the response. The static indentation results indicate that the presence of damage causes the response to change as it requires more force to cause the same amount of indentation when damage is present. This is attributed to the ability of the surface of the damaged laminate to better conform to the indentor. However, the global response was unaltered by the presence of damage as the force and displacement versus time histories were not affected. This is in part attributable to the fact that the size of the damage is an order of magnitude smaller than the length important in the structural response. However, the forces in these impact events were below those forces in the static indentation test where there was a significant difference in the behavior between the undamaged and predamaged cases. It is therefore likely that differences would be seen in the force versus time history for more severe impact events.