American Institute of Aeronautics and Astronautics 1 A Comparison of Triaxially Braided Composites Using the Generalized Method of Cells John W. Hutchins 1 Mississippi State University, Mississippi State, MS 39762 Kuang C. Liu 2 Arizona State University, Tempe, AZ 85287 Thomas E. Lacy, Jr., Ph.D. 3 Mississippi State University, Mississippi State, MS 39762 Aditi Chattopadhyay, Ph.D. 4 Arizona State University, Tempe, AZ 85287 and Brett A. Bednarcyk, Ph.D. 5 NASA Glenn Research Center, Cleveland, OH, 44135 Two distinct triaxial braid architectures are compared in this numerical study: (1) the “traditional” triaxial braid in which the axial tows are merely laid in between the woven biased (±θ°) tows and (2) the “true” triaxial braid in which the axial tows are interleaved through the biased tows. The microstructure of the triaxial braids is constrained as a function of volume fraction, braid angle, and tow geometries. A multiscale modeling methodology is developed to use the Generalized Method of Cells (GMC) micromechanics model recursively over multiple length scales in a three step homogenization process to compare the effective elastic properties of the two different types of triaxial braids. This methodology has previously been used to accurately predict experimental results for the “traditional” triaxial braid architecture; however, this paper simply compares the two types of braid architectures numerically. Preliminary results show that the “true” triaxial braid follows most of the trends of the “traditional” triaxial braid in effective stiffness properties as a function of braid angle, except for the axial modulus at higher braid angles. At braid angles in excess of 45°, the “true” triaxial braid shows an increase in axial stiffness. The axial modulus of the “true” triaxial braid exceeds that of the “traditional” triaxial braid for braid angles greater than 50°. Therefore, the “true” triaxial braid does present a viable alternate braid that may offer advantages over the “traditional” triaxial braid for certain applications. An experimental study is being prepared to compare the two triaxial braids experimentally and to validate the numerical model used in the present study. Nomenclature GMC = Generalized Method of Cells (micromechanics theory) RUC = Repeating Unit Cell w a = axial tow width w b = biased tow width t a = axial tow thickness t b = biased tow thickness s a = axial tow spacing s b = biased tow spacing V f = volume fraction 1 Ph.D. Student, Department of Aerospace Engineering, 330 Walker Engineering Building. 2 Ph.D. Student, Department of Mechanical and Aerospace Engineering. 3 Associate Professor, Department of Aerospace Engineering, 330 Walker Engineering Building. 4 Professor, Department of Mechanical and Aerospace Engineering. 5 Materials Research Engineer, Mechanics and Life Prediction Branch, 21000 Brookpark Rd. 51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference<BR> 18th 12 - 15 April 2010, Orlando, Florida AIAA 2010-2520 Copyright © 2010 by John W. Hutchins. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.