PSI - Issue 13

Ahmed Sohail et al. / Procedia Structural Integrity 13 (2018) 450–455 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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2. Modeling Methodology

2.1. Geometric modeling

The finite element model of the impact behavior of 3D hybrid woven composite is modeled using commercial FE modelling software ABAQUS. The architecture of composite panel included three warp (0 0 ) and four weft (90 0 ) plies stacked as a cross-ply laminate. Warp and weft fibers are bounded together by z-yarns which run in the warp fiber direction from top to bottom to bind all the layers. Out of seven layers of the composite laminas, 4 layers are made up of S2 glass and the other 3 of carbon fibers. Schematic of the architecture for a unit cell of 3D hybrid woven composite is shown in Fig 1. The warp and weft yarn number 1 and 2 are made up of S2 glass fiber and remaining fibers are made up of carbon fiber. The overall size of the panel is 100 x 100 mm 2 with the thickness of 4.1 mm approximately. A spherical steel projectile with diameter of 5.5mm and 0.706 of mass is selected as an impactor.

Z-yarn

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Warp

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Fig. 1. Schematic representation of weave architecture in one Unit-cell of 3D hybrid woven composite

2.2. FE modeling and failure criteria Each lamina or ply is modeled as a solid plate with the thickness of 0.586 mm and during the section assignment, a continuum shell section was assigned which is discretized with 8-node quadrilateral continuum shell element (SC8R) with reduced integration where single element through the thickness of each ply is used. A structured meshing strategy was used keeping the element size smaller at the impact and probable damage location to capture the damage behavior more accurately. Moreover, appropriate element size is chosen so that the z-yarns can be incorporated at specified distances where they are present in actual geometry. Impactor was modeled as rigid body while assigning the appropriate inertial mass (0.706g) through reference point and discretized as 4-node 3D bilinear quadrilateral rigid elements (R3D4). Z-yarns were modeled as 3D connector elements (CONN3D2) with 2 nodes, where these connector elements run throughout the composite plate in a zig-zag configuration. The response of the theses elements is modeled as linear elastic spring-like behavior until the onset of damage. Stress based failure criterion was used, once the failure stress is reached in particular direction the connector element fails at instance. Hashin damage failure criteria is used to predict the damage initiation in the composite laminas, Hashin (1980), Hashin and Rotem (1973), and a damage evolution response is used to model the damage evolution process. Damage initiation refers to the onset of degradation at a material point. In Abaqus the damage initiation criteria for fiber-reinforced composites are based on Hashin's theory. These criteria consider four different damage initiation mechanisms: fiber tension, fiber compression, matrix tension, and matrix compression, ABAQUS 6.14 (2014). Delamination between two adjacent laminas is modeled by the cohesive zone model with the traction separation law where surface-based cohesive behavior is defined as a surface interaction property.