PSI - Issue 18

Boris Fedulov et al. / Procedia Structural Integrity 18 (2019) 399–405 Boris Fedulov and Alexey Fedorenko / Structural Integrity Procedia 00 (2019) 000–000

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5. Example problem To demonstrate the algorithm of damage parameters distribution to get the worst case, let us consider the compression problem of composite plate with dimensions 200mm×200mm and total thickness of 8mm formed by 40 layers of quasi-isotropic layup [0°/45°/-45°/90°] 5S . Fig. 3 shows the placement of crack and optimizing volume, which is a cylinder of diameter 50mm with one non-damaged, and consequently, not optimized layer at the side of impact. The loading was applied through displacement to get better convergence of numerical analysis. Displacements were chosen to get deformation of the layup to be 2%, which is near the failure one. The direction of compression loading is 0° degree. Solid elements with incompatible modes (perform close to second-order elements for regular element shape) were used with grid density of one element per layer. Crack is placed in the middle of the specimen thickness, between 0° and 90° degree layers (Fig. 3 red line). The energy spent on damage was chosen as ܧ ݊ ൌ ͳͲ J.

Fig. 3. Problem statement scheme with middle crack placement

After 5 iterations, the result is shown Fig.4, it is possible to say that tendency is to remove stiffness from layers with orientation of fiber reinforcement of 90°.

Fig. 4. Damage parameter distribution with middle crack after 5 iterations

After 10 iterations, stiffness of the damaged volume was reduced essentially and specimen buckled. This made algorithm to redistribute damage parameters inside the optimizing volume (Fig. 5).