PSI - Issue 17

Michał Kwietniewski et al. / Procedia Structural Integrity 17 (2019) 58–63 Michał Kwietniewski / Structural Integrity Procedia 00 (2019) 000 – 000

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Discretization methods.

Aramid wrap

Elastomeric matrix

Elastomeric core

Fig. 2. Discrete model in a partial cross-section

The model adopted for the analysis consisted of: a cylinder that simulated the core fiber, a spiral imitating the wrap fiber and a cylinder-shaped matrix model, which contained the HAY model inside. The discrete model development was started from generating a 2D mesh of the entire model cross-section. Then the mesh was the basis for creating a 3D model by extruding to 5.89 mm and discretizing the model into finite elements. In the next steps, each element layer was rotated by the appropriate angle to form the helical wrapped weave. In addition, stitching of all adjacent model nodes was obtained. It reduced the problems of contact between the model parts. The preparation of the discrete model was carried out in the Hyper Mesh software. The discrete model in a partial cross-section was shown in Fig. 2. The wrap fiber was wrapped around the core once, giving a slope angle of 30  over the length of 5.89 mm. The diameters of created models were as follows: core diameter - 0.62 mm, wrap diameter - 0.46 mm, outer diameter of the matrix - 2.4 mm. Finally , the discrete model consisted of 94140 HEX 8 type elements and 97737 nodes. The model included the lack of direct contact between the core and wrap fibers. It is due to two reasons. When composite is produced in real by impregnating fabrics with a liquid resin, the gaps between the components are deleting. Also in the analysed model, the space between the model parts was filled with an elastomeric matrix what was shown in Fig. 3. This also positively effects numerical calculations. Near the place where fibers are contacting, it was possible to use eight-node (cube) elements instead of six-pitch (prism) as reported by Piechna (2011) and LS-dyna keyword user's manual volume I (2002). The shape of finite elements in the immediate vicinity of fibers was shown in Fig. 3.

Fig. 3. The ground plane of the discrete model with the zoom of the fibers contact region.