Impact analysis g…/… Assessment of residual strength Compression after impact analysis The impacted panel was then subjected to in-plane compression using displacement control to assess the residual strength after impact. For this progressive failure static analysis, MSC NASTRAN was used as a stress solver. The deformed mesh, as a result of impact, along with accumulated damages and residual stresses were used as initial conditions in the compression analysis. Figures 6a and 6b show the initial impacted panel and the final fractured panel Fig. 6: Damage distribution (a) before and (b) after in-plane compression of the composite panel subjected to compression along with the damage modes. Figure 6b indicates that the final failure of the composite panel is due to the delamination, fibre micro-buckling (crippling of bottom skins), longitudinal/transverse compression, modified distortion energy, and the previously observed out-of-plane transverse/ longitudinal shear stresses. The test data indicated that the residual strength of such a panel after impact was 23.28 kips (228.29 N) and the major failure mechanism was asymmetric crippling of the bottom skin. The assessed residual strength from the progressive failure analysis was 24.68 kips (242.03 N) (see figure 7) and Fig. 7: Compressive load versus displacement The peak represents the residual strength of the composite panel. crip-pling of the bottom skin along with other failure modes. The analysis predicted the residual strength of the composite panel within 6% of the test data – a reasonably good prediction for composite structures. The composite panel strength in compression was also evaluated without impact. The analysis results indicate that the overall strength is reduced by a factor of 2.25 because of the damage produced by the impact event. Contact: Rose Ragalini roseragalini@alphastarcorp.com JEC Composites Magazine / No37 December 2007http://www.jeccomposites.com