Bending capacity of multi-layered FRP pipelines during offshore installation

The Fiber Reinforced Polymeric (FRP) pipelines have higher strength than steel, and excellent fatigue behavior and corrosion resistance. Because of their superior performance in mechanical loads and corrosive environment, they are a good choice for offshore applications. Since FRP materials are anisotropic and the pipelines are multilayered, the calculation of stresses is difficult. Stress analysis can be performed numerically with the aid of commercial software packages. However, the numerical solutions are approximate and the parametric study is problematic. In the present work, an analytical solution for bending stress calculation of multilayered FRP pipelines during offshore installation is presented. Typical examples are solved and bending capacity of multilayered FRP pipelines versus the fiber orientation angle and number of layers is provided and discussed.

IMPACT RESPONSE ANALYSIS OF COMPOSITE PLATE WITH DIFFERENT FIBER ORIENTATION ANGLES

In this study, we established an analytical model of rectangular plate as a carbon fiber reinforced plastic (CFRP) fan blade, and simulated propagation of strain due to a foreign object collision such as a bird strike. The effect of fiber orientation angles was investigated as one method to reduce the propagating strain. In this model, large deflection caused by bird-striking is considered and nonlinear vibration equation derived from Rayleigh-Ritz method was integrated using Newmark-β method. It was shown that the strain propagates to the spanwise tip of the fan blade and causes detrimental damage there. It was also suggested that changing the fiber orientation angle of CFRP can reduce the strain transmitted to the tip of fan blade.

Parametric Study of a Composite Skin for a Twist-Morphing Wing

Although the benefits of morphing wings have been proven in many studies in the last few decades, the wing skin design remains one of the challenges to advancing and implementing the morphing technology. This is due to the conflicting design requirements of high out-of-plane stiffness to withstand aerodynamic loads and low in-plane stiffness to allow morphing with the available actuation forces. Advancements in the design of hybrid and flexible composites might allow for design solutions that feature this balance in stiffness required for this application. These composites offer new design parameters, such as the number of plies, the fiber-orientation angle of each ply in the skin laminate, and the spatial distribution of the plies on the skin surface. This paper presents a parametric study of a composite skin for a twist-morphing wing. The skin is made of periodic laminated composite sections, called “Twistkins”, integrated in an elastomeric outer skin. The twisting deformation is localized in the elastomeric sections between the Twistkins. The design parameters considered are the number of plies in the composite Twistkins, the fiber-orientation angle of the plies, the torsional rigidity of the elastomer, the width ratio, and the number of elastomeric sections. The computational analysis results showed that the torsional compliance can be increased by increasing the width ratio, decreasing the number of elastomeric sections, number of composite plies and the elastomer’s torsional rigidity. However, this would also lead to a decrease in the out-of-plane stiffness. The nonlinearity and rates at which these parameters affect the skin’s behavior are highlighted, including the effect of the fiber-orientation angle of the laminate plies. Hence, the study guides the design process of this twist-morphing skin.

Modal Characterization of Sandwich Skew Plates

The current work focuses on the experimental and finite element free vibration studies of laminated composite sandwich skew plates. The comparison was made between the experimental values obtained by the Fast Fourier transform (FFT) analyzer and a finite element solution obtained from CQUAD8 finite element of The MacNeal-Schwendler Corporation (MSC) / NASA STRucture Analysis (NASTRAN) software. The influence of parameters such as aspect ratio (AR) (a/b), skew angle (α), edge condition, laminate stacking sequence, and fiber orientation angle (θ°) on the natural frequencies of sandwich skew plates was studied. The values obtained by both the finite element and experiment approaches are in good agreement. The natural frequencies increase with an increase in the skew angle for all given ARs.

Parametric Optimization of Isotropic and Composite Axially Symmetric Shells Subjected to External Pressure and Twisting

The present paper is devoted to the problem of the optimal design of thin-walled composite axially symmetric shells with respect to buckling resistance. The optimization problem is formulated with the following constraints: namely, all analyzed shells have identical capacity and volume of material. The optimization procedure consists of four steps. In the first step, the initial calculations are made for cylindrical shells with non-optimal orientation of layers and these results are used as the reference for optimization. Next, the optimal orientations of layers for cylindrical shapes are determined. In the third step, the optimal geometrical shape of a middle surface with a constant thickness is determined for isotropic material. Finally, for the assumed shape of the middle surface, the optimal fiber orientation angle θ of the composite shell is appointed. Such studies were carried for three cases: pure external pressure, pure twisting, and combined external pressure with twisting. In the case of shells made of isotropic material the obtained results are compared with the optimal structure of uniform stability, where the analytical Shirshov’s local stability condition is utilized. In the case of structures made of composite materials, the computations are carried out for two different materials, where the ratio of E1/E2 is equal to 17.573 and 3.415. The obtained benefit from optimization, measured as the ratio of critical load multiplier computed for reference shell and optimal structure, is significant. Finally, the optimal geometrical shapes and orientations of the layers for the assumed loadings is proposed.

Buckling characteristics of cut-out borne composite stiffened hyperbolic paraboloid shell panel

The present study investigates buckling characteristics of cut-out borne stiffened hyperbolic paraboloid shell panel made of laminated composites using finite element analysis to evaluate the governing differential equations of global buckling of the structure. The finite element code is validated by solving benchmark problems from literature. Different parametric variations are studied to find the optimum panel buckling load. Laminations, boundary conditions, depth of stiffener and arrangement of stiffeners are found to influence the panel buckling load. Effect of different parameters like cut-out size, shell width to thickness ratio, degree of orthotropy and fiber orientation angle of the composite layers on buckling load are also studied. Parametric and comparative studies are conducted to analyze the buckling strength of composite hyperbolic paraboloid shell panel with cut-out.

Effect of fiber orientation angle on patch repaired composite plates

Stress intensity factors numerically investigated the Mode I loading of composite plates with an edge crack and repaired with a patch on a single side. The effect of the fiber orientation angle for both composite plate and the patch were analyzed with regard to crack length, adhesive properties, and plate thickness. The stress intensity factors were calculated by using the quarter point element that can be applied to 3D crack problems of homogeneous anisotropic materials.It was observed in this study that the fiber orientation angle affects the stress intensity factors significantly.

Flutter analysis of a sandwich composite beam using an analytical method

In this paper, the aeroelastic behavior of a composite wing is investigated in the compressible flow using the analytical method. The composite wing is simulated as a thin-walled single-cell closed cross-section beam with circumferentially asymmetric stiffness (CAS) configuration. The best layup configuration for the maximum flutter speed is determined by analyzing four layups configuration where the fiber orientation angle varies within the range of 0–90 degrees. Moreover, an included foam layer between composite layers resulted in higher bending stiffness and improved stability characteristics of the wing. It was shown that there is a significant improvement in the flutter speed for [Formula: see text] layup. Numerical results demonstrate the advantages of foam filled model over the model without foam in terms of the flutter speed to the weight ratio.

Structural Design and Dynamic Analysis of Carbon Fiber Reinforced Plastic Shaft with Metal Parts

It is important to improve dynamic performance of rotating machinery by reducing the mass of shaft and increasing the natural frequency. Many studies have focused on dynamic characteristics of shaft in rotating machinery with the utilization of composite material. This paper mainly investigates the structural design and dynamic analysis of a CFRP/Metal hybrid shaft. The finite element method (FEM) has been used to determine the selection of design variables include fiber orientation angle, layers stacking sequence and layers thickness. Also, experimental test was carried out using a FFT analyzer with impact hammers. The differences between the FEM analysis result and the experiment test result were respectively less than 4.5% and 6.3% for the first two natural frequencies; therefore, the results of FEM analysis are acceptable. The results reveal that the fiber orientation angle is the most significant factor affecting the dynamic characteristics of CFRP/Metal hybrid shaft. In addition, there have some effect of the layer stacking sequence on natural frequency.