7 Composite Fuselage Impact Testing and Simulation: A Model Calibration Exercise 77 260 Shape 1 Test Analysis Shape 2 250 240 230 220 210 200 50 −50 0 50 −50 0 260 250 240 230 220 210 200 260 250 240 230 220 210 200 50 −50 0 50 −50 0 260 250 240 230 220 210 200 Fig. 7.12 Qualitative comparison of the first two measured and predicted impact shapes; first column shape 1 and second column is shape 2 10 1 Velocity (in/sec) Theta y (pitch) Theta x (roll) ERODS GAB,GCA,GBC EB (lbs/in2) EA (lbs/in2) 0.9 0.8 0.7 0.6 0.5 0.4 Variance Contribution Disp. Norm (in) 0.3 0.2 0.1 0 0 0.002 0.004 0.006 0.008 0.01 Time (sec) 0.012 0.014 0.016 0.018 0.02 5 0 Fig. 7.13 Sensitivity results for fuselage model Unfortunately, it is very difficult to set ERODS values based on component test data. An optimization search for a parameter set to minimize the error between displacement test and analysis was unable to reduce the displacement norm error to less than 1.22 in. For most parameter values the error was well within 1:22=p3inches in any particular direction. Overall, in order to reconcile the analysis with test results one needs to consider both tests: vibration and impact. Recall that the vibration test results suggested that the modulus of the material needed to be reduced to 71 % of their original values
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