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CONTENTS
Volume 4, Number 1, March 2022
 


Abstract
This paper presents a novel hierarchical micromechanics model to simulate Sheet Molding Compound (SMC) composites with wavy fibers. The three-step homogenizations are integrated to calculate the effective properties of SMC chips, layers, and composites, respectively. During homogenization, it has a unique capability of modeling the wavy fibers within fiber chips through a rotational transformation. The orientation and overlapping of the fiber chips caused by the manufacturing process are considered through the proposed multi-site (MS) micromechanics model. Furthermore, J2 plasticity and Lemaitre-Chaboche ductile damage models are adopted to estimate the nonlinear behavior of SMC composites. The nonlinear behavior of SMC composites is predicted based on the concurrent simulations at each homogenization. The comparison with results from experiments and the literature validates the proposed hierarchical model. Finally, a parametric study investigates the effects of fiber waviness and chip orientation on the effective behavior of SMC composites.

Key Words
fiber waviness; Mori-Tanaka; multiscale modeling; random distribution; sheet molding compound

Address
Fei-Yan Zhu: Department of Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul, 08826, Korea
Hyoung Jun Lim: Department of Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul, 08826, Korea
Hoil Choi: Department of Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul, 08826, Korea
Gun Jin Yun: Department of Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul, 08826, Korea; Institute of Advanced Aerospace Technology, Seoul National University, Gwanak-gu, Seoul, 08826, Korea

Abstract
In the present work, several studies related to the failure of laminated composite material plates are discussed. To carry out those studies, two models were developed: an analytical one, implemented in a symbolic computation system, MAPLE(R) and a numerical one implemented in ANSYS(R). The main objective is the calculation of the load that originates the first ply failure in the plates studied, considering the criteria of Maximum stress and Tsai-Wu. Five case studies were considered, with different stacking sequences, different lamina thicknesses, and different arrangements and materials. Symmetrical and non-symmetrical layups were considered. The load cases comprise uniaxial and biaxial in-plane forces. The expected tension-extension and tension-bending coupling effects were also discussed.

Key Words
composite material; failure criteria; failure index; laminated plates

Address
Samuel N. Mula: CIMOSM, Centro de Investigação em Modelação e Otimização de Sistemas Multifuncionais, ISEL, IPL, Instituto Superior de Engenharia de Lisboa, Av. Conselheiro Emídio Navarro 1, 1959-007 Lisboa, Portugal
Afonso M.S. Leite: CIMOSM, Centro de Investigação em Modelação e Otimização de Sistemas Multifuncionais, ISEL, IPL, Instituto Superior de Engenharia de Lisboa, Av. Conselheiro Emídio Navarro 1, 1959-007 Lisboa, Portugal
Maria A.R. Loja: CIMOSM, Centro de Investigação em Modelação e Otimização de Sistemas Multifuncionais, ISEL, IPL, Instituto Superior de Engenharia de Lisboa, Av. Conselheiro Emídio Navarro 1, 1959-007 Lisboa, Portugal; IDMEC, IST-Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal

Abstract
Macro periodic composite structures are often represented by large-scale finite element (FE) models, so conventional FE methods and component mode synthesis (CMS) techniques are inadequate for assessing the dynamics of these structures in a reasonable amount of time. This study proposes the improved reduction system (IRS) combined with a substructuring scheme for modal analysis of periodic composite structures; and compares it with the homogenization method. Model reduction and homogenization are performed utilizing in-house code and ANSYS(R), respectively. In IRS-based substructuring, the macrostructure is subdivided into identical substructures, then a single representative volume element (RVE) is taken and reduced. The reduced substructures are assembled into a macrostructure with fewer degrees of freedom (DOFs), resulting in an accurate and efficient result with a small memory footprint. According to our findings, the proposed method provides accurate results independent of the number of substructures contained within the macrostructure, whereas the homogenization method relies on the number of substructures present.

Key Words
homogenization; IRS; periodic composite structures; RVE; substructuring

Address
Robel Weldebrhan Hagos: Department of Mechanical Engineering, Kumoh National Institute of Technology, Daehak-ro 61, Gumi, Gyeongbuk 39177, Korea
Geomji Choi: Department of Mechanical Engineering, Kumoh National Institute of Technology, Daehak-ro 61, Gumi, Gyeongbuk 39177, Korea
Heejun Sung: Multiscale Mechanical Design Division, School of Mechanical and Aerospace Engineering, Seoul National University, 1 Gwanak-ro, Seoul 08826, Korea
Seongmin Chang: Department of Mechanical Engineering, Kumoh National Institute of Technology,Daehak-ro 61, Gumi, Gyeongbuk 39177, Korea; Department of Mechanical Design Engineering, Kumoh National Institute of Technology,
Daehak-ro 61, Gumi, Gyeongbuk 39177, Korea

Abstract
Understanding and characterizing the tensile behavior of short fiber reinforced polymer composites (SFRPCs) under high temperature environments and dynamic loadings is of great significance for their wide application. In this work, a temperature and strain rate dependent tensile strength model is developed, based on the modified rule of mixture and the Force-Heat Equivalence Energy Density Principle. The combined effects of component properties, fiber length, fiber orientation, residual thermal stress, temperature and strain rate are taken into account. The proposed model is proved to be efficient in predicting the tensile strength of SFRPCs under a wide range of temperatures and strain rates, through the comparison between the experimental data and model predictions. Furthermore, based on the present model, the influencing factors analysis of tensile strength of SFRPCs and its evolution with temperature and strain rate is investigated and discussed. This work provides a solid theoretical basis for the design, optimization and tensile property prediction of SFRPCs under extreme conditions.

Key Words
analytical modeling; short fiber reinforced polymer composites; strain rate; temperature; tensile strength

Address
Yong Deng: School of Civil Aviation, Northwestern Polytechnical University, Xi'an 710072, China; Collaborative Innovation Center of NPU, Shanghai 201100, China; Yangtze River Delta Research Institute of NPU, Taicang 215400, China
Yi Hao: School of Civil Aviation, Northwestern Polytechnical University, Xi'an 710072, China
Chao Zhang: School of Civil Aviation, Northwestern Polytechnical University, Xi'an 710072, China
Yangming Cao: Silicon Content Technology Co., Itd, Beijing 100095, China
Weiguo Li: College of Aerospace Engineering, Chongqing University, Chongqing 400044, China

Abstract
This paper investigates vibration response of functionally graded multilayer polymer composite beams reinforced by graphene platelets and subjected to uniform temperature rise. Different distribution patterns of graphene platelets (GPLs) accounting for uniform and non-uniform in the polymer matrix are considered. The effective Young's modulus, mass density and Poisson's ratio are evaluated through the modified Halpin-Tsai approach which takes into account the size effects of the graphene reinforcements. Within the framework of the classical beam theory, the governing equations are derived by applying the Hamilton's principle and then solved by using an analytical method based on Fourier series. Obtained outcomes indicate that with a low amount of the GPLs reinforcement can dramatically improve the stiffness of the beams, and GPLs rich at the bottom and the top of the beam can be considered as the best reinforcing effect. A comprehensive parametric study is conducted to examine the effects of distribution pattern, weight fraction, and geometry of GPL, temperature change, as well as total number of layers on the maximum frequency of functionally graded multilayer GPLRC beams.

Key Words
composite beam; dynamic analysis; graphene nanoplatelets; Halpin-Tsai law; nanocomposite; thermal load

Address
Ismail Bensaid, Ahmed Saimi and Ihab Eddine Houalef: Mechanical engineering Department, Faculty of Technology, IS2M Laboratory, University of Abou Beckr Belkaid (UABT), Tlemcen, Algeria

Abstract
This paper investigates the effects of constituents' properties (i.e., stiffness ratio, volume fraction, and interfacial stiffness) on the viscoelastic behavior through the mean-field-based micromechanics model. The stress prediction of the proposed micromechanics model for the viscoelastic composites is verified through the direct numerical simulation (DNS) using a finite element model with different volume fractions, materials properties, and interphase layers. The stress prediction accuracy is studied under cyclic loading conditions. The stress prediction accuracy is better when the volume fraction is lower and the interphase layer is modeled. Finally, the effects of the constituent's properties, volume fraction, and interfacial imperfection on the tangent delta and relaxation behavior of the composites are examined.

Key Words
homogenization; Mori-Tanaka method; micromechanics; particulate composites; viscoelastic behavior

Address
Hangil You: Department of Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul, 08826, Korea
Gun Jin Yun: Department of Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul, 08826, Korea; Institute of Advanced Aerospace Technology, Seoul National University, 08826, Seoul, Korea


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