MDS-FT: Fatique

We consider a composite tailcone exhaust subjected to noise vibration, which is modeled as a cyclic pressure load on its upper surface as shown in Figure 1 (bottom right). The tailcone attachment is modeled using springs. Four cut-outs used for attachment of the tailcone give rise to stress concentration and damage initiation. The fiber architecture depicted in Figure 1 (bottom right).

Figure 1 (top) shows distribution of the damage parameter as function of number of cycles. Elements which were totally damaged at the micro-scale were deleted giving rise to fatigue crack growth. The damage initiated in the vicinity of the cut-out and propagated along the attachment. The number of load steps that were needed to perform the analysis using the adaptive block cycle scheme in MDS-FT was about 10000 whereas a cycle-by-cycle simulation would have required about 75 million load steps corresponding to life prediction of 1.5 million load cycles.

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Figure 2 compares MDS-FT life prediction results against experimental data for 1Hz and 60Hz load frequencies at various load amplitudes and temperatures. The test coupon is assumed to be failed once the damage in either of matrix phase or tow phase reaches a critical value.