Finite element analysis of composite structures

Finite element analysis of composite structures with smart constrained layer damping

Four methods for global sensitivity analysis are studied with respect to their applicability in the finite element analysis of composite structures: (1) sensitivities based on the variance conditional expectation involving experimental design, (2) Morris' elementary effects method (including recent improvements to effective trajectory selection), (3) Sobol's main and total sensitivity indices, and (4) the root mean square of approximate derivatives at sampled points. The sensitivities of the first ten natural frequencies to the composite material properties as well as to the ply stack are determined. The methods are compared and an assessment of their applicability is made in the case of a fairly large number (d > 25) of uncertain parameters.

Stochastic finite element analysis of composite structures based on material microstructure

A mechanics-based modeling approach is developed to rapidly predict damage in polymer matrix composites resulting from a low velocity impact event. The approach is incorporated into a computer code that provides an efficient means to assess the damage resistance for a range of material systems, layup configurations, and impact scenarios. It is envisioned that the developed approach will aid in early design and analysis of composite structures where sizing and layup decisions must be made, and evaluating the feasibility of a large number of laminate configurations using numerical approaches such as finite element analysis (FEA) is prohibitively expensive. Therefore, the goal of the modeling approach is to predict the impact damage size given the laminate configuration and impact scenario. This information can then be used to determine the residual strength of the material. To be useful in such a context, the tool is designed to run quickly (<2 minutes) to allow a large number of design cases to be investigated. The results presented demonstrate that the model is capable of efficiently predicting low velocity impact damage size, shape, and location within an acceptable accuracy suitable for preliminary design and analysis of composite structures.

1R16. Analysis of Composite Structures. - C Decolon (Dept of Mech, Conservatoire Natl des Arts et Metiers, France). Hermes Sci Publ, Paris. Distributed in USA by Taylor &amp; Francis Publ, New York NY. 2002. 336 pp. ISBN 1-56032-982-3. $135.00.Reviewed by E Armanios (Sch of Aerospace Eng, Georgia Inst of Tech, Atlanta GA 30332-0150).This book, comprising three parts and four appendices, provides a mathematical presentation of the governing equations for laminated composite plates and beams. The first part is devoted to the anisotropic constitutive relationships with emphasis on orthotropic materials. Hygrothermal effects are covered. Maximum stress and strain failure criteria are presented as well as Tsai-Hill, Tsai-Wu, and Hoffman polynomial based criteria. The second part treats laminated plates. The governing equations for thin plates based on the Kischhoff-Love assumptions are presented first. Symmetric orthotropic plates are studied for the cases of bending, vibration, and buckling. The stiffness coefficients for asymmetrical cases are presented as well. Bending, vibration, and buckling is presented for thin plates with asymmetric cross-ply as well as asymmetric balanced stacking sequences. Thermo-elastic behavior is considered through the derivation of the 3D and plane stress constitutive relationships for orthotropic off-axes layups. Applications to balanced and symmetric laminates are presented. Moderately thick orthotropic symmetric plates are analyzed using Reissner-Mindlin assumptions. Cylindrical bending of thin and moderately thick laminated plates is presented for the cases of bending, vibration, and buckling. The third part considers symmetrical beams starting with axial loading and followed by bending, including transverse shear strain effects. Applications to bending, vibration, and buckling are provided. Four appendices are devoted to the derivation of the governing equations for laminated plates. In the first two appendices, the governing equations of small and large transverse displacements of plates are derived by integrating the equations of motion. The third and fourth appendices use a variational formulation to obtain the governing equations for laminated plates based on Kirchoff-Love and Reissner-Mindlin assumptions, respectively. The book aims at presenting the basis for the analysis of composites structures. As such, minimum derivation of equations is provided mainly in appendices. The focus is on the mathematical presentation of governing equations and closed-form solutions. The book is suited as a reference for graduate students and practitioners of mechanics of laminated composites. Its appealing feature is the systematic and compact presentation of the governing equations of beams and laminated composite thin and moderately thick plates including small and large transverse displacements, into a single reference. The figures adequately illustrate the boundary and loading conditions associated with the development of the governing equations. None of the equations are numbered making it difficult at times to follow the mathematical presentation sequence across sections and chapters. The inclusion of references to specific works by some investigators would enhance the author’s presentation and comments within the text of the book. Analysis of Composite Structures should be a good reference for purchase by graduate students and practicing scientists and engineers.

State of the art of composite structures in non-deterministic framework: A review

This paper deals with a modeling of the composite timber-concrete ceiling structure. In the analysis of the composite structure, there is the slip using the contact elements and volume finite elements considered. Numerical modeling is complemented by an analytical calculation. This article aims to determine the stiffness of a particular type of glued strip. Totally eight models of the composite timber-concrete structure have been studied.

This paper proposes a new approach for the FE analysis of composite structures by means of 1D refined models that have been derived in the framework of the Carrera Unified Formulation (CUF). CUF provides hierarchical higher-order structural models with arbitrary expansion orders. Taylorand Lagrange-type polynomials were used to interpolate the displacement field over the element cross-section. The proposed new approach, referred to as Composite-Wise (CW), is able to provide stress and strain fields with solid-like accuracy and very low computational cost. Within the CW approach, different scale components (fiber, matrix, laminae and laminates) can be simultaneously considered in the same structural model. Failure analyses are conducted by implementing well-known failure criteria. Furthermore, an integral evaluation of failure parameters is introduced to determine critical portion of the structure where failure could take place. Results are provided to show the enhaced capability of the present formulation in the failure analysis of fiber-reinforced composite structures by the detection of detailed displacement/stress fields with reduced computational cost.

The article presents a finite element based study of linear and geometrically non-linear progressive failure analysis of thin walled composite aerospace structures subjected to combined in-plane and out-of-plane loading which are typically encountered in thin walled aerospace structures. Different ply and constituent based failure criteria and material property degradation schemes have been coded into a PCL code in Nastran. As case studies, progressive failure analyses of sample composite laminates with cut-outs under combined loading are executed to study the effect of geometric non-linearity on the first ply failure and progression of failure. Different ply and constituent based failure criteria and different material property degradation schemes are also compared in terms of predicting the first ply failure and failure progression. For mode independent failure criteria, a method is proposed for the determination of separate degradation factors for fiber and matrix failures which are assumed to occur simultaneously. The results of the present study, show that under combined out-of-plane and in-plane loading, depending on the load case linear analysis can significantly underestimate or overestimate the failure progression compared to geometrically non-linear analysis even at low levels of out-of-plane loading.

The characteristics of composite materials are of high importance to engineering applications; therefore the increasing use as a substitute for conventional materials, especially in the field of aircraft and space industries. It is a known fact that researchers use finite element programs for the design and analysis of composite structures, use of symmetrical conditions especially in complicated structures, in the modeling and analysis phase of the design, to reduce processing time, memory size required, and simplifying complicated calculations, as well as considering the response of composite structures to different loading conditions to be identical to that of metallic structures. Finite element methods are a popular method used to analyze composite laminate structures. The design of laminated composite structures includes phases that do not exist in the design of traditional metallic structures, for instance, the choice of possible material combinations is huge and the mechanical properties of a composite structure, which are anisotropic by nature, are created in the design phase with the choice of the appropriate fiber orientations and stacking sequence. The use of finite element programs (conventional analysis usually applied in the case of orthotropic materials) to analysis composite structures especially those manufactured using angle ply laminate techniques or a combination of cross and angle ply techniques, as well considering the loading response of the composite structure to be identical to that of structures made of traditional materials, has made the use of, and the results obtained by using such analysis techniques and conditions questionable. Hence, the main objective of this paper is to highlight and present the results obtained when analyzing and modeling symmetrical conditions as applied to commercial materials and that applied to composite laminates. A comparison case study is carried out using cross-ply and angle-ply laminates which concluded that, if the composition of laminate structure is pure cross-ply, the FEA is well suited for predicting the mechanical response of composite structure using principle of symmetry condition. On the other hand that is not the case for angle-ply or mixed-ply laminate structure.

Composite structure often shows undesirably significant uncertainty in its mechanical properties, which may consequently result into large stochastic variation of its natural frequency. This study provides stochastic natural frequency analysis of typical composite structures based on micro-scale (constituent-scale) and meso-scale (ply-scale) uncertainty. Uncertainty propagation across micro-scale and meso-scale is investigated. Response surface method (RSM) based on finite element modeling is employed to obtain approximate natural frequency of structures with complex shape or boundary conditions, and mean value and standard deviation of natural frequency of composite plate and cylindrical shell are derived. Differences in natural frequency statistics of composite plates and cylindrical shells derived by considering uncertainty at different scales are quantified and discussed. Significant statistical correlation between ply elastic properties and ply density is observed, and the statistical correlation is demonstrated to lay great influence on the statistics of structure natural frequency.

High performance 3D-analysis of thermo-mechanically loaded composite structures

Extended multiscale finite element method for large deflection analysis of thin-walled composite structures with complicated microstructure characteristics

Locking-free curved elements with refined kinematics for the analysis of composite structures

Dynamic loading of composite structures with fluid–structure interaction