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Effect of Platelet Filler and Void Contents to the Mechanical Properties of Composites Timothy A. Fay (Akkerman, Inc.) Tye B. Davis (Link Manufacturing, Inc.) Jin Y. Park (Minnesota State University) November 22, 2011

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Presentation Outline Objectives of the Research Problem Description Conventional Approaches Evaluation Procedure of the Proposed Method Comparison and Discuss

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Objectives of the Research Review conventional analytical approaches Consider the filler and void contents as analytical/design parameters for polymer composites Define the effects of platelet fillers and voids Propose effective methods to evaluate mechanical properties

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Without an Analytical Model? Material Fabrication Properties by Testing Primitive Design Heterogeneous Materials Properties OK? Product NO YES

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Need a reliable analytical method to obtain the properties of composites containing fillers/voids prior to the fabrication!

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Analytical Modeling of Polymer Composite Materials Matrix Models Roving Layer Models CSM Layer Models

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Micromechanical Structure of Pultruded FRP E-glass Roving + Matrix E-glass CSM + Matrix Resin + Filler + Voids + +

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Composite Properties Matrix Properties (or Particle composites) Resin Voids Fillers Roving Layers Roving fibers CSM fibers CSM Layers Conventional Approach Our Approach

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Clay Filler Particle

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Why Fillers? More Stability (Reduce Void Content) More Stiffness/Strength What kind of Fillers? Ceramic, Boron Nitride, Graphite, Alumina

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Analysis of Matrix (Mixture of Resin, Filler and Void) Volume fractions of resin, fillers and voids in Matrix Filler models (platelet and spherical models) Void model (spherical model) Properties of isotropic material containing inhomogeneities (micromechanical models) This approach can be used for particle composites

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Matrix with Circular Platelet Filler Model Model #1 Unidirectional (theoretical) Model 3-D Random Model

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Unidirectional Fillers: Macroscopically Transversely Isotropic Material Evenly distributed Fillers

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Transversely Isotropic Materials [C ij ]=Stiffness Matrix

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[C][C] [C’]=[T x ][C][T x ] T

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Transformation Matrix about the x-axis by angle Stiffness of Matrix having randomly (evenly) rotated platelet fillers about the x-axis Transformed Stiffness about the x-axis

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Transformation Matrix about the y-axis by angle Transformed Stiffness about the y-axis Stiffness of Matrix having randomly (Evenly) rotated platelet fillers about the y-axis

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Stiffness Matrix Having Random 3-D Platelet Fillers

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Extensional Modulus of the Matrix with 3-D Randomly Oriented Platelet Fillers Shear Modulus of the Matrix with 3-D Randomly Oriented Platelet Fillers where

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Procedure to obtain Matrix Properties by Model #1 Obtain E x (= E y ), E z, xy (= yx ), zx G xy (=G yx ), G zx of transversely isometric matrix using Chamis (1984) and Halpin-Tsai (1969) Step 3 Include voids in the matrix using analytical models Step 1

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Modified Mori-Tanaka Model - For spherical (or randomly oriented ellipsoidal) inclusions - For randomly oriented voids: G i = K i = 0

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Platelet Filler & Spherical Void Model The matrix model is very close to the actual material structure The obtained properties agree well with the experimental results Randomly oriented ellipsoidal voids can be assumed as spherical inclusions [Que 1992]

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Spherical Filler and Void Model Easy and Quick Method to Obtain Matrix properties Randomly oriented ellipsoidal voids can be assumed as spherical inclusions Is it really OK to assume the platelet shaped fillers as spherical inclusions?

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Matrix Properties Volume fractions of the constituents were provided by Composites Lab, Material Engineering, Georgia Institute of Technology

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STACKING SEQUENCE OF VP25 STACKING SEQUENCE OF VS25 STACKING SEQUENCE OF VS50 Provided by Strongwell, Inc.

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Composite Properties Matrix Properties Resin Voids Fillers Roving Layers Rovin g fibers CSM fibers CSM Layers

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Properties of Roving Layers Volume Fractions of Fibers and Matrix in the Roving Layer Chamis (1984) and Halpin-Tsai (1969) Models Properties of CSM Layers Volume Fractions of Fibers and Matrix in the CSM Layer Tsai-Pagano (1968) Models

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Properties of Pultruded Composites where

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Properties of Pultruded Composites where

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ASTM D 5379 Shear Test Specimens (4” x.75” x.25”)

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G 12 exp /G 12 computed G 12 exp was determined by following ASTM D 5379

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G 12 exp /G 12 computed 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Pl-Es-ChPl-Es-HTPl-MT-CHPl-MT-HTPl-SC-ChPl-SC-HT Micromechanical Models G 12 exp /G 12 computed Group VP25 Group VS25 Group VS50

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Conclusions Analytical models for polymer composite matrix having platelet fillers and voids were successfully established. Conventional analytical equations can be modified for matrix models and particle composites. The assumption of platelet fillers and spherical voids is valid for the composites under consideration. All of the Analytically computed properties are higher than experimentally determined results.

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All of the analytically computed properties are higher than experimentally determined values. Initial damage in resin-matrix Interfacial debonding Multi-stacks Why?/Future study

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References Ma, H., Hu, G. and Huanr, Z., “A Micromechanical Method for Particulate Composites with Finite Particle Concentration, “ Mechanics of Materials, 36: 359–368, 2004 Geckeler, K. E. and Rosenberg, E., Functional Nanomaterials, American Scientific Publishers, Stevenson Ranch, CA, 2006 Mura, T. Micromechanics of Defects in Solids, Martiuns Nijhoff, Boston, MA., 1987 Technical Report: Material Properties, Southern Kaolin Clay Inc., TX Park, J. Y., Fay, T. A. and Davis, T. B., " A Study on Clay Particle Effect to the Mechanical Properties of Pultruded Composites under Shear Loading," ASME International Congress and Exposition, Seattle, WA, 2007 Park, J. Y. and Fay, T. A., “Mathematical Modeling of Nanocomposite Properties Considering Nanoclay/Epoxy Debonding,” Journal of Reinforced Plastics and Composites, 29: 1230-1247, 2010 ASTM Standard D 5379 (2002). ASTM

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