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A transient dynamic finite element procedure is presented for failure analysis of centrally‐impacted laminated composite pretwisted rotating plates. A nine‐noded, three‐dimensional degenerated composite shell element is developed and used for the present finite element formulation. Effects of transverse shear deformation and rotary inertia are included. The strength‐of‐material type failure criteria are adopted and the “total ply discount” approach is used as the stiffness reduction model. The dynamic equilibrium equation is derived by applying Lagrange’s equation of motion and the investigation is carried out for moderate rotational speeds for which the Coriolis effect is negligible. The modified Hertzian contact law is utilized to compute the contact force between the impactor and the laminated plate. Impact failure analyses of pretwisted rotating plates are performed to investigate the effects of angle of twist, rotational speed and laminate configuration.

Delamination is a common and crucial damage mode which occurs during manufacturing of layered composites or their service life. Its existence leads to degradation in mechanical properties or even structural failure of composites. Hence, the purpose of this article is to study the effect of induced delamination on flexural performance of CFRP composites.

In this article, the flexural behaviors of intact and delaminated carbon/epoxy laminates were investigated under pure bending. A circular PTFE film was introduced during fabrication to create artificial delamination. Moreover, finite element models were developed for intact and delaminated composites using ANSYS. The created models were discretized using 3D structural eight node solid elements.

The delamination influenced considerably flexural properties of composite. The composite exhibited a linear elastic nature prior to the damage of top ply on the compression side. The flexural strength and stiffness of the composite reduced to 44.5% and 18.2% respectively due to the existence of artificial delamination. The results of four point bending experiments and finite element analysis agreed for both intact and delaminated composites within acceptable error. Finally for same composites, first ply failure analysis was carried out using Tsai-Hill, Tsai-Wu and Hashin failure criteria.

In pure bending, beam section of the middle portion is free from shear. It is not so in case of three-point bending. Hence, the effect of embedded artificial defect on bending performance of CFRP composite due to pure bending has been investigated.

Many studies only take into account the ply stacking sequence as the design variable to determine the optimal ply drop-off location; however, it is necessary to optimize other parameters that have a direct influence on the ply drop-off site such as which plies should be dropped and in which longitudinal direction. That way, the purpose of this study is to find the most significant design variables relative to the drop-off location considering the transversal and longitudinal positions, seeking to achieve the optimal combination of ply drop-off locations that provides excellent performance for the laminate plate.

This study aims to determine the optimal drop-off location in a laminate plate using the finite element method and an approach statistical with design of experiments (DOE).

The optimization strategy using DOE revealed to be satisfactory for analyzing laminate structures with ply drop-offs, demonstrating that not all design factors influence the response variability. The failure criterion response variable revealed a poor fit, with an adjusted coefficient of determination lower than 60%, thus demonstrating that the response did not vary with the ply drop-off location. Already the strain and natural frequency response variables presented high significance. Finally, the optimization strategy revealed that the optimal drop-off location that minimizes the strain and maximizes the natural frequency is the ply drop-off located of the end plate.

It was also noted that many researchers prefer evolutionary algorithms for optimizing composite structures with ply drop-offs, being scarce to the literature studies involving optimization strategies using response surface methodology. In addition, many studies only take into account the ply stacking sequence as the design variable to determine the optimal ply drop-off location; however, in this study, the authors investigated other important parameters that have direct influence on the ply drop-off site such as which plies should be dropped and in which longitudinal direction.

This paper presents a novel approach to the design of composite flywheels. Specifically, the paper determines the optimal orientation of fibers in a stacked ply composite disk arrangement. The equations of equilibrium represent the state equations for the system. Classical lamination theory is used to develop the constitutive relations for the composite disk. This allows the orientation of the fibers in the reinforcement ply to be treated as the control variable for the problem. The Tsai‐Wu criterion, which is used to predict failure of the flywheel, is taken as the performance index. Solutions to the optimal control problem yield disk designs that provide energy densities that are 13 percent greater than a benchmark design.

The objective of the present work is to present the design optimization of composite cylindrical shell subjected to an axial compressive load and lateral pressure.

A novel optimization method is developed to predict the optimal fiber orientation in composite cylindrical shell. The optimization is carried out by coupling analytical and finite element (FE) results with a genetic algorithm (GA)-based optimization scheme developed in MATLAB. Linear eigenvalue were performed to evaluate the buckling behaviour of composite cylinders. In analytical part, besides the buckling analysis, Tsai-Wu failure criteria are employed to analyse the failure of the composite structure.

The optimal result obtained through this study is compared with traditionally used laminates with 0, 90, ±45 orientation. The results suggest that the application of this novel optimization algorithm leads to an increase of 94% in buckling strength.

The proposed optimal fiber orientation can provide a practical and efficient way for the designers to evaluate the buckling pressure of the composite shells in the design stage.

The purpose of this study is to check the reliability of a multi-pin joint to be a fail-safe joint by considering different geometric and material parameters. The pin joints are made of uni-directional fiberglass that has been impregnated with epoxy composites incorporating 3% nano-clay.

This study incorporates the analysis of multi-pin joints experimentally, numerically and statistically using the Weibull approach. During analyses, geometrical parameters edge to diameter (E:D), longitudinal pitch to diameter (F:D), side edge to diameter (S:D) and transverse pitch to diameter (P:D) were analyzed using the Taguchi method with a higher-the-better L16 orthogonal array.

This study aims to develop multi-pin laminated joints to attain higher reliability, which have been designated as fail-safe joints for the intended application and which have higher joint strength. The study reveals that to achieve 99% reliability or 1% probability of failure using the Weibull approach, 24.4% load decrement from the experimental result recorded for three-pin joint configuration at E:D = 4, F:D = 5, S:D = 4 and P:D = 5. Similarly, for the four-pin configuration at E:D = 4, F:D = 4, S:D = 4 and P:D = 5, 23.07% of load decrement observed from the experimental result implies that the expected load with a 99% reliability offers a safe load.

A reliability analysis on multi-pin joints was not conducted in structural application. Composite materials are used because of high reliability and high strength-to-weight ratio. So, in the present work, reliability of the multi-pin joint is analyzed using Weibull distribution.

The purpose of the paper is to improve the calculability of a continuum damage failure model of composite laminates based on Tsai-Wu criteria.

A technique based on viscous regularization, a characteristic element length and fracture energies of fiber and matrix are used in the model.

The calculability of the material model is improved. The modified model can predict the behavior of composite structure better.

The convergence problem and the mesh softening problem are main concern in the calculability of numerical model. In order to improve the convergence, a technique based on viscous regularization of damage variable is used. Meanwhile, characteristic element length and fracture energies of fiber and matrix are added into the damage constitutive equation to reduce the mesh sensitivity of numerical results. Finally, a laminated structure with damages is implemented using a User Material Subroutine in ABAQUS/Standard. Mesh sensitivity and value of viscosity are discussed.

This study aims to address a deep statistical analysis on transtibial prostheses made of composite isogrid carbon/epoxy structure.

For the methodological procedure, an experimental arrangement was created using design of experiments, and the response surface methodology (RSM) was used. The RSM was obtained from the decision variables of the isogrid model, which consists of angle, circular width and helical width. All modeling was performed numerically using the finite element method.

Results obtained through analysis of variance (ANOVA) indicated the sensitivity of each decision variable (manufacture) in the mechanical responses. The results obtained in this study provide a starting point in formulating optimization problems for researchers and engineers.

A noteworthy thing about structural analysis and structural optimization is that some parameters and decision variables are more significant than others in certain responses (Major et al., 2011). Knowing the sensitivity of these parameters is essential for the correct formulation of an optimization problem. To handle these obstacles, design of experiments and ANOVA are used to solve and obtain the main effects on the structural performance. Nevertheless, to the best of the authors’ knowledge, very few efforts have been devoted to the development to show the factors that influence the various responses of a lower limb prosthesis isogrid tube.

This paper aims to focus on calculating the number of layers of composite laminates required to take the applied load made up of graphite/epoxy (AS4/3501-6) which can be used in many industrial applications. Optimization for minimization of weight by variation in the mechanical properties is possible by using different combinations of fiber angle, number of plies and their stacking sequence.

Lots of research studies have been put forth by aerospace industry experts to improve the performance of aircraft wings with weight constraints. The orthotropic nature of the laminated composites and their ability to characterize as per various performance requirements of aerospace industry make them the most suitable material. This leads to necessity of implementing most appropriate optimization technique for selecting appropriate parameter sets and material configurations.

In this work, exhaustive enumeration algorithm has been applied for weight minimization of fiber laminated composite beam subjected to two different loading conditions by computing overall possible stacking sequences and material properties using classical laminate theory. This combinatorial type optimization technique enumerates all possible solutions with an assurance of getting global optimum solution. Stacking sequences are filtered through Tsai-Wu failure criteria.

Finally, through the outcome of this optimization framework, eight different combinations of stacking sequences and 24-ply symmetric layup have been obtained. Furthermore, this 24-ply layup weighing 0.468 kg has been validated using finite element solver for given boundary conditions. Interlaminar stresses at top and bottom of the optimized ply layup were validated with Autodesk’s Helius composites solver.

Wind turbines are one of the best candidates to solve the problem of increasing energy demand in the world. The aim of this paper is to apply a multi-objective structural optimization study to a Phase II wind turbine blade produced by the National Renewable Energy Laboratory to obtain a more efficient small-scale wind turbine.

To solve this structural optimization problem, a new Non-Dominated Sorting Genetic Algorithm (NSGA-II) was performed. In the optimization study, the objective function was on minimization of mass and cost of the blade, and design parameters were composite material type and spar cap layer number. Design constraints were deformation, strain, stress, natural frequency and failure criteria. ANSYS Composite PrepPost (ACP) module was used to model the composite materials of the blade. Moreover, fluid–structure interaction (FSI) model in ANSYS was used to carry out flow and structural analysis on the blade.

As a result, a new original blade was designed using the multi-objective structural optimization study which has been adapted for aerodynamic optimization, the NSGA-II algorithm and FSI. The mass of three selected optimized blades using carbon composite decreased as much as 6.6%, 11.9% and 14.3%, respectively, while their costs increased by 23.1%, 29.9% and 38.3%. This multi-objective structural optimization-based study indicates that the composite configuration of the blade could be altered to reach the desired weight and cost for production.

ACP module is a novel and advanced composite modeling technique. This study is a novel study to present the NSGA-II algorithm, which has been adapted for aerodynamic optimization, together with the FSI. Unlike other studies, complex composite layup, fiber directions and layer orientations were defined by using the ACP module, and the composite blade analyzed both aerodynamic pressure and structural design using ACP and FSI modules together.