Design and Analysis of Composite Structures

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.

Development of concurrent engineering system for design of composite structures

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.

Dynamic loading of composite structures with fluid–structure interaction

Polymers and polymer composites in construction: Edited by L.C. Holloway Published by Thomas Telford, 1990

PurposeThe purpose of this paper is to investigate the mechanical properties’ behaviors of woven composite cut-out structures with specific parameters. Because of the complexity of micro-scale and meso-scale structure, it is difficult to accurately predict the mechanical material behavior of woven composites. Numerical simulations are increasingly necessary for the design and optimization of test procedures for composite structures made by the woven composite. The results of the proposed method are well satisfied with the results obtained from the experiment and other studies. Moreover, parametric studies on different plates based on the stacking sequences are investigated.Design/methodology/approachA multi-scale modeling approach is suggested. Back-propagation neural networks (BPNN), radial basis function (RBF) and least square support vector regression are integrated with efficient global optimization (EGO) to reduce the weight of assigned structure. Optimization results are verified by finite element analysis.FindingsCompared with other similar studies, the advantage of the suggested strategy uses homogenized properties behaviors with more complex analysis of woven composite structures. According to investigation results, it can be found that 450/−450 ply-orientation is the best buckling load value for all the cut-out shape requirements. According to the optimal results, the BPNN-EGO is the best candidate for the EGO to optimize the woven composite structures.Originality/valueA multi-scale approach is used to investigate the mechanical properties of a complex woven composite material architecture. Buckling of different cut-out shapes with the same area is surveyed. According to investigation, 45°/−45° ply-orientation is the best for all cut-out shapes. Different surrogate models are integrated in EGO for optimization. The BPNN surrogate model is the best choice for EGO to optimization difficult problems of woven composite materials.

An advanced strength and life prediction tool, MAE, was developed for the analysis and design of composite structures and components. The MAE integrates three theories and methods: micromechanics of failure (MMF), an accelerated testing method (ATM) and an evolution of damage (EOD). The MAE can serve as a useful tool to predict damage initiation, progression and life under various durability loading and environmental conditions. It can handle the inhomogeneous complex geometries and structural components such as open-hole, filled-hole, bonded/bolted joint, stiffened panel, textile, etc. Therefore, it can help select not only the material and laminates but also optimal geometrical configurations. The MAE modules were implemented and integrated with a commercial finite element software, Abaqus, for better reliability and maintainability. Several examples of strength and life predictions of open-hole and double-edge notched specimens demonstrated the capability of the MAE as an advanced tool for the composite durability design. Nomenclature i t = time at the i-th step i t ∆ = subtime segment f E = stiffness of fiber constituent m E = stiffness of matrix constituent f v = volume fraction of fiber T ∆ = difference between operation and cure temperatures c = moisture content f t = time to failure ) (e f t = time to failure for an element (e) i D = damage fraction at time i t ) ( ) ( i e t D = partial damage fractions at time for an element (e) i t 1 I = first invariant of microstress vM σ = von Mises microstress σ

Multilayer composite structures have the characteristics of high strength, high stiffness, and good corrosion resistance, and are increasingly used in underwater equipment. The stability analysis of multilayer composite structures is one of the key issues in engineering design. As an important analysis method, the analytical calculation method can achieve rapid design of structural parameters. This paper proposes an analytical method for stability calculation of multilayer composite structures based on residual pressure recursion. Through numerical experiments, the effectiveness of the method is verified, providing an option for stability analysis and engineering design of multilayer composite structures.

Lightweight design and crash analysis of composite frontal impact energy absorbing structures

The performances of low-velocity impact (LVI) and compression after impact (CAI) of honeycomb sandwich composite panels are investigated experimentally and numerically. Honeycomb sandwich panels with different facesheet thicknesses are impacted by drop-weight machine under gradually increasing impact energies. The visible surface damage is recorded and ultrasonic C-scan technology is used to inspect the internal damage of sandwich plates. Numerical simulation is conducted using finite element method, taking into account both facesheet damage and honeycomb damage. The facesheet damage model is based on the continuum damage mechanics and cohesive zone model to simulate intralaminar and interlaminar damage respectively. The honeycomb damage model, which takes into account of both compressive damage and shear damage, is addressed and verified by three-point bending experimental tests. The numerical results show good agreements on LVI and CAI with the experiments, thus verifying the validity of the presented numerical model. Then we use the numerical model to simulate the LVI properties of sandwich plates under compressive and tensile preloading. We conclude that the interlaminar delamination damage of facesheet easily evolves under compressive preloading while intralaminar fiber fracture damage could expand under tensile preloading. The conclusion in our article could be useful to the design and analysis of composite sandwich structures.

Artificial hail ice impact damage of laminated composite T-joint with stitching reinforcement

13 - Design and testing of crashworthy aerospace composite components

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.

The paper presents a theoretical and experimental study of the influence of damage accumulation in composite material on the elastic fourth-rank tensor and on the strength under quasi-static, cyclic and dynamic loads. Layered polymer composites (glass or carbon fiber-reinforced plastic) are considered. This work aims to develop a mathematical model that accounts for the impact of damage in the composite material on the fourth-rank tensor of elastic properties. The constitutive relations for an orthotropic composite material are proposed, taking into account the accumulation of damage during tensile or shear loading. A numerical simulation using the finite element method is done for a periodicity cell for composite variants (unidirectional, layered, etc.) to determine the effective elastic properties. Quasi-static loading experiments were conducted on composite samples (carbon plastic) to validate the model and the degradation of elastic properties was determined by measuring the longitudinal sound speed. The full-scale experiments confirmed that damage accumulation in carbon fiber-reinforced plastic leads to the degradation of its effective elastic properties. In this connection, a technique was developed to take into account irreversible damage in an orthotropic composite material through the components of the ductility tensor, which may be helpful for the design and analysis of composite structures. The findings of the study could help with the creation of new materials with enhanced mechanical characteristics, as well as with raising the quality of already-existing materials. The developed mathematical model of orthotropic composite material can be used to enhance the structural strength properties and boost the application safety in a variety of industry.

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