PSI - Issue 13

Ahmed Sohail et al. / Procedia Structural Integrity 13 (2018) 1014–1019 Author name / StructuralIntegrity Procedia 00 (2018) 000 – 000

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at micro level is consisted of several layers of [0/90] laminates which are bounded together by z-yarn which runs along the warp (0 0 ) direction. High through the thickness and in-plane stiffness and strength, superior delamination resistance is the result of the addition of z-yarn in most of the cases. By adding or replacing the fiber tows with those of different materials, the enhanced material properties can be achieved for 3D woven composites. Hybridization for the carbon-fiber 3D woven composite has shown improved notch sensitivity, better impact resistance and improvement in fracture toughness Munoz et al. (2014). However, some problems associate with these kinds of 3D architectures like during the manufacturing process of liquid resin molding pockets with rich resin and voids are likely to occur. Due to the crimping of fiber tows during weaving process it is more likely that mechanical properties of the overall material can be degraded, and most importantly complex architecture makes it difficult for the designers to predict the mechanical properties for such kind of materials. In order to mechanically characterize the 3D woven composites, one way is to simplify the complex structure without compromising on the overall structure characteristics, some examples are binary model, unit-cell, and mosaic model, developed in the past. The mechanical characterization of 3D woven composites can be evaluated by either experiments or through a predictive analytical or numerical modeling approach. Predictive modeling approach is an inexpensive method as compared to the experimental techniques. Since the analytical models are based on assumptions in order to simplify the structure and the problem, which (assumptions) can be greatly reduced in the case numerical simulations. The mechanical behavior of 3D woven composites has been investigated by many authors in the past. Tan et al. (2000b) conducted an experimental investigation into the tensile behavior of 3D orthogonal CFRP composites. A comparison of tensile properties of 3D woven composites with other fiber structures such as 2D weaves and 2D laminates have been presented by Stig and Hallström (2009), Lomov et al. (2009) and Ivanov et al. (2009). Stiffness and strength behavior was also analyzed for 3D woven composite by many researchers in the past by analytical means. Bogdanovich AE (2006) presented a homogenized 3D mosaic model to estimate the stiffness and strength of 3D woven composites. Similarly, Tan et al. (2000a) and Naik et al. (2001) presented analytical models based on iso-stress/iso-strain models for 3D woven composites to predict the elastic and strength properties. Computational modeling was also carried out for the elastic and stiffness parameters. Bogdanovich AE (2006) presented 3D Mosaic model for progressive failure analysis at RVE level to predict the strength parameters. To simulate the elastic and strength parameters in a detailed numerical analysis, Dai and Cunningham (2016), developed three different models, unit cell model, FE mesoscale model and a mosaic model. Experimental, analytical and numerical means are extensively used for the mechanical properties of 3D woven composites, however for 3D hybrid woven composites there are few comprehensive studies available on this topic. Munoz et al. (2014) performed experimental studies on deformation and failure mechanism of carbon/glass 3D hybrid woven composites. Pankow and Yen (2012) presented the experimental results on the tensile response of Carbon/glass/Kevlar 3D woven composite. Apropos, the current study is directed on investigating the effect of hybridization of 3D woven composite for elastic and strength parameters. At first a baseline 3D woven composite structure with fiber tows of carbon/epoxy was selected which is experimentally analyzed by Bogdanovich AE et al. (2013). Numerical model is validated and established with the help of finite element based generalized micro-mechanics tool. In the second part hybridization of baseline structure is achieved by inclusion of Kevlar fiber tows in a certain ratio. The combination of the two types of fibers has been investigated through finite element simulation to determine the overall mechanical response of the combined hybrid 3D woven composite.

2. Geometry and finite element modeling 2.1. Geometric modeling

The geometry of 3D woven composites performs a leading role in estimating their mechanical and failure properties. The weft and warp fiber tows spread in-plane throughout the panel with little or no undulation. 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. A detail study has been presented by Karahan et al. (2010) where internal geometry of the fibers in a 3D woven structure is characterized. The same architecture is being used in the current study, schematic of the weave architecture are shown in Fig 1.