Analysis Of Composite Structures Research Articles

Viscoelastic modeling and creep behavior analysis of composite bistable column-shell structures based on model validation technology

Anti-symmetric composite bistable structures have both efficient storage capacity and high mechanical properties, gaining widespread attention in engineering fields. In this paper, the effect of the viscoelastic behavior on the second stable-state curvature of the composite bistable column-shell structure is investigated. First, a method to determine viscoelastic parameters is proposed by model validation technology. Digital image correlation (DIC) technology is adopted to test the creep behavior of bistable composite structures and provide effective experimental data for model validation. Finally, the viscoelastic parameter identification results are used to establish a finite element model of the composite bistable structure for studying the creep behavior of the structure. Several simulation and experiment examples show that the theoretical and finite element model of the composite bistable column-shell structure established by the proposed method can accurately obtain the structural creep behavior.

Seismic Response Analysis of Composite Isolation Structures with Non-classical Damping

Seismic Response Analysis of Composite Isolation Structures with Non-classical Damping

Geometrically nonlinear topology and fiber orientation optimization of composite structures using membrane-embedded model

The membrane-embedded model can be efficiently used in the finite element analysis of composite structures considering geometrical nonlinearity because of its practicability. This paper extends this model to the topology and fiber orientation optimization considering geometrical nonlinearity. The discrete design variables of topology and fiber orientation are continuous by the solid isotropic material with penalization method and bi-value coding parameterization method. An optimized interpolation scheme for the membrane-embedded model is constructed for geometrical nonlinearity. The filtering function is added to improve the convergence of the fiber orientation. To reduce the computational complexity, topology and fiber orientation are independently updated at each iteration during the optimization process. Numerical examples demonstrate the effectiveness of the proposed method for membrane-embedded composite considering geometrical nonlinearity.

Dimension reduction and homogenization of composite plate with matrix pre-strain

This paper focuses on the simultaneous homogenization and dimension reduction of periodic composite plates within the framework of non-linear elasticity. The composite plate in its reference (undeformed) configuration consists of a periodic perforated plate made of stiff material with holes filled by a soft matrix material. The structure is clamped on a cylindrical part. Two cases of asymptotic analysis are considered: one without pre-strain and the other with matrix pre-strain. In both cases, the total elastic energy is in the von-Kármán (vK) regime ( ε 5 ). A new splitting of the displacements is introduced to analyze the asymptotic behavior. The displacements are decomposed using the Kirchhoff–Love (KL) plate displacement decomposition. The use of a re-scaling unfolding operator allows for deriving the asymptotic behavior of the Green St. Venant’s strain tensor in terms of displacements. The limit homogenized energy is shown to be of vK type with linear elastic cell problems, established using the Γ-convergence. Additionally, it is shown that for isotropic homogenized material, our limit vK plate is orthotropic. The derived results have practical applications in the design and analysis of composite structures.

Analysis of structural composition and antioxidant activity of traditional fermented sour meat peptides

Chinese traditional fermented sour meat has a unique flavor and nutritional value. The antioxidant activity of sour meat peptides is related to their molecular weights, amino acid compositions, and structural characteristics. Therefore, this study explores the relationships between them. The results indicate that sour meat peptides with molecular weights <1 kDa exhibit significant antioxidant properties both in vitro and in vivo. The smaller the molecular weights, the higher the content of typical amino acids with antioxidant activity (p <0.05), and the characteristic peaks of ultraviolet absorption decrease. The absorption peak at 284.5 nm blue-shifted, and the polarity of the microenvironment increased. The peak intensity and peak area of the Raman characteristic peaks of tyrosine residues and aliphatic amino acids were enhanced. In the secondary structure, there is a high content of β-turns and a low content of α-helix, which are closely related to the enhancement of antioxidant activity.

Incomplete dissolved behavior and mechanical analysis of SnAgCu-SnBi composite solder structures for high-reliable package-on-package techniques

Due to the development of advanced packaging technology such as Package on Package (POP), traditional Sn-Ag-Cu (SAC) solder can no longer meet the demand. Utilizing the differences in temperature and performance of various solder materials to create composite structures for soldering is an effective method to achieve PoP interconnection. In this research, the microstructure of the interface between SAC305 and liquid in the incomplete dissolved solider ball was observed, and the grain orientation after solidification was analyzed. In addition, the effect of SnBi ratios on the microstructure and mechanical properties of SAC305-SnBi composite solder balls, and the fracture mechanism was analyzed according to the fracture morphology. The results show that according to Electron Backscatter Diffraction (EBSD) analysis, the grain size of Sn-Ag-Cu-Bi is small, and the orientation tends to be the same. With the rise in SnBi content, the eutectic structure in the solder ball exhibited a progressive increase and the IMC at the interface gradually changed from uneven rod-like structure to more uniform scallop-like structure. When the weight fraction of SnBi is 66.7%, the shear strength researches a maximum value of 62.2 MPa. As the SnBi content increases, there is an observable shift in the fracture location from the IMC to the solder.

Analytical and numerical analysis of composite sandwich structures with additively manufactured lattice cores

In this study, an analytical and numerical analysis of a hybrid sandwich structure with a lattice core produced by additive manufacturing with composite facesheets is carried out. This paper aims to analytically calculate the mechanical behavior of the hybrid sandwich structure under three-point bending and to verify the results by the finite element method. The analytical method used in this article for the analysis of the composite sandwich structure is the First-Order Shear Deformation Theory (FSDT). The numerical analysis of the hybrid sandwich structure was performed in ANSYS. In the analyses, homogenized models of lattice structures, which had been previously validated, were employed to reduce the number of elements and thereby save time during the solution process. As a result of the study, an extensive investigation into the deformation, shear, and normal stress values of sandwich structures with lattice cores of varying aspect ratios has been carried out. The findings suggest a potential for optimization in lightweight structures, which could lead to innovative advancements in design and manufacturing processes within the aerospace and automotive sectors.

Підхід до визначення напружено-деформованого стану стрижнів з композиційних матеріалів з урахуванням внутрішнього самоврівноваженого напруженого стану

The subject of this research is methods of stress-strain state analysis of composite structures. The goal is to develop a mechanism to explain the phenomenon of warping of thin-walled composite sections with a non-uniform cross-section under thermal loading and to synthesize a model to determine the forces in the section elements. The objectives of this study are to predict the deformed states of composite sections at the manufacturing stage and to determine the temperature stresses that occur at the manufacturing stage, as well as after the assembly of the structure. The methods used are related to the mechanics of materials and structures. The following results were obtained. The possible deformation forms of composite plates with an asymmetric structure are analyzed and the rationale for the appearance of such deformations is given. A model of the force interaction of elements in a folded section is proposed. The proposed model can be extended to most sections of load-carrying aircraft structures. Based on the analysis of the mechanics of thin-walled folded sections, the mechanism of the occurrence of complex bending-torsional deformation of long-dimensional sections made of composites with a non-uniform cross-section under the action of an internal self-equilibrium stress state caused by a change in temperature or shrinkage of the binder or both is explained. The analysis of this mechanism makes it possible to design composite sections with minimal warping and to propose engineering methods to compensate for unwanted spatial movements in the case of arbitrary loading of section elements. Conclusions. The scientific novelty of the obtained results can be summarized as follows. A mechanism for the deformation of rods made of dissimilar composite materials when the temperature changes (after extraction from the tool or during operation) is proposed considering the difference in Poisson's coefficients. A model for determining the forces acting on the perimeter of section elements was synthesized, and the corresponding formulas were obtained, which form the basis for the theory of off-center compression of rods. The direction of further research in this field is currently being planned.

A geometrically nonlinear Hellinger–Reissner shell element for the postbuckling analysis of variable stiffness composite laminate structures

A geometrically nonlinear Hellinger–Reissner shell element for the postbuckling analysis of variable stiffness composite laminate structures

Connection strength analysis for composite fuselage gate structures of civil aircraft

Civil aircraft boarding gate is an important channel for passengers to enter and exit the aircraft, and is also an important part of the aircraft structure, with the function of maintaining cockpit pressure. Traditional boarding doors are made of metal, and with the large number of composite materials used in the bearing structure of civil aircraft, composite boarding doors are also used in new civil aircraft. The strength of the connection inside the new composite boarding gate is related to the safety of passengers and crew. This paper focuses on the connection problem of the internal structure of composite boarding gate, aiming to analyze its connection strength under working conditions. This paper establishes a real finite element model of the boarding gate according to the loading condition and force transmission characteristics of the civil aircraft door and analyzes the connection strength of the structure such as the skin and the transverse and longitudinal beams, the skin and the side frame, the transverse and longitudinal beams connection, and the stop block in turn. The study shows that the strength of the connecting structures of the boarding gate designed by using composite materials is reasonable and can meet the service requirements of the boarding gate, thus demonstrating the rationality of the boarding gate structure designed with composite materials.

The Different Properties of Geopolymer Composites Reinforced with Flax Fibers and Carbon Fibers.

The main motivation for this research was to improve the properties of geopolymers by reinforcement using synthetic and natural fibers, and to gain new knowledge regarding how the nature and/or the quantity of reinforcement fibers influences the properties of the final geopolymers. The main objective was to investigate the effects of different types of reinforcement fibers on the properties of the geopolymers. These reinforcement fibers were mainly environmentally friendly materials that can be used as alternatives to ordinary Portland cement. The authors used fly ash and river sand as the raw materials for the matrix, and added carbon fibers (CF), flax fibers (FF), or a hybrid of both (CFM) as reinforcements. The samples were prepared by mixing, casting, and curing, and then subjected to various tests. The main research methods used were compressive strength (CS), flexural strength (FS), water absorption (WA), abrasion resistance (Böhme's disk method), microstructure analysis (SEM), chemical composition (XRF), and crystal structure analysis (XRD). The results showed that the addition of fibers partially improved the mechanical properties of the geopolymers, as well as reducing microcracks. The CF-reinforced geopolymers exhibited the highest compressive strength, while the FF-reinforced geopolymers showed the lowest water absorption. The authors, based on previous research, also discussed the factors that influence fiber-matrix adhesion, and the optimal fiber content for geopolymers.

Модель накопления повреждений в ортотропном композиционном материале

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.

Buckling Failure Analysis of Slender Composite Structure with Telescopic Boom and Truss

Buckling Failure Analysis of Slender Composite Structure with Telescopic Boom and Truss

The effect of the stress equilibrium factor on the composite case of the solid rocket motor

In this paper, based on the composite structure design and analysis software ANSYS ACP, the layup design for the composite cases of the equal pole hole solid rocket motor with different stress equilibrium factors is carried out. The finite element software ANSYS Workbench is used to study in detail the effects of stress equilibrium factor on the stress level, failure degree, and burst pressure prediction of the case under a certain internal pressure. The results show that reducing the value of the stress equilibrium factor can reduce the stress level of each winding layer along the main direction of the material in the motor case and gradually transfer the maximum stress of the case along the fiber direction from the weak stress zone to the cylinder section. This is beneficial for improving the burst pressure of the case and making the burst point located in the cylinder section. However, whether the case failure is related to the selected failure theory and strength criterion, the failure results and burst pressure obtained using different failure theories and strength criteria may be different, which indicates that each failure criterion has its scope of application and limitations. Under the Tsai-Wu criterion, using the stress equilibrium equation to calculate the stress equilibrium factor can just ensure that each winding layer of the motor case does not fail under the working pressure. In summary, when designing a composite case and predicting its failure, in addition to considering whether the stress equilibrium factor taken is conducive to meeting the design requirements for the strength of the case, it is also necessary to consider the use of multiple failure criteria to study the failure of the case. Obviously, arbitrarily selecting the stress equilibrium factor is not appropriate in the above process. By analyzing the influence of the stress equilibrium factor on the strength and failure condition of the motor case, it can provide an effective reference for the design of a composite case for SRM.

Non-geodesic winding design method for the composite shell of unequal-pole-hole solid rocket motor

Advanced composite materials have the advantages of high specific strength, high specific modulus, good fatigue resistance, good shock absorption performance, and strong designability. They are widely used in the fields of national defense science and technology and civil engineering. To make a more accurate winding design of the composite shell of the non-equidistant solid rocket motor, based on the ANSYS ACP composite structure design and analysis software, this paper uses the cubic spline function method to design the fiber winding thickness of the shell head section for a solid rocket motor. The Runge-Kutta method is used to calculate the changing winding angle of the non-geodesic line, and the changing winding angle and winding thickness on the head are simulated based on the look-up table interpolation table module in ACP. Finally, the mechanical properties of the designed shell under certain internal pressure are simulated and analyzed. Through the simulation analysis of the designed engine model, it is found that the connection between the front head and the barrel section is a weak profit, and the follow-up study should reinforce this area.

Vibration analysis of active composite structures embedded with long and short shape memory alloy (SMA) fibers

The shape memory effect (SME) is a source of internal compressive stresses that modify the vibration behavior of shape memory alloy (SMA) embedded composite structures. Generally, long fibers are used due to their suitability for activating SMA using resistive heating. Longer SMA fibers embedded in composite structures have their limitations in design and manufacturing. Minimal research work has been done on tuning the vibration behavior of composite structures embedded with short SMA fibers. In this research paper, an analytical model for evaluating the natural frequencies of an SMA embedded composite beam has been proposed. Effects of various design parameters for long (continuous) and short (discontinuous) SMA fibers embedded in composites have been investigated. It was observed that short SMA fibers with a higher aspect ratio can tune their frequencies similarly to long SMA fiber composites and are more effective in thicker beams. Matrix material with negative coefficient thermal expansion is more suitable for embedding SMA for modifying natural frequency in active mode.

Continuous tow shearing for the automated manufacture of defect-free complex 3D geometry composite parts

It has always been challenging to manufacture a composite structure with complex geometry using automated fibre placement (AFP) process. The tool surface is difficult to be tessellated using fibre tapes with a finite width, without producing gaps and overlaps, and fibre steering along non-geodesic fibre paths produces various defects such as tape buckling and pull-up. In this work, a defect-free fibre-steering process on a complex surface was demonstrated by realising the continuous tow shearing (CTS) process in three dimensions. A new head control algorithm was developed, which defines the head orientations and trajectories based on the pin-jointed net model to manipulate the fibre tow using both in-plane shear and out-of-plane twisting deformations. Fibre steering process utilising this new algorithm was tested on a doubly-curved surface, using an industrial robot arm equipped with a CTS prototype head, and its layup quality and accuracy were assessed by using a three-dimensional laser profile scanner. An experimental comparison with the conventional AFP process showed that the new control algorithm enables defect-free fibre steering on complex 3D surfaces allowing for simplifying the design and analysis of novel composite structures.

A Constitutive Model for Stud Connection in Composite Structures

The complexity of finite element analysis for composite structures can be significantly reduced by representing the connector and adjacent concrete as a macroscopic element. Nevertheless, the prevailing macroscopic models for shear connections predominantly employ nonlinear elastic theory. This approach introduces inaccuracies in estimating structural stiffness and load-bearing capabilities, primarily due to its inability to precisely capture the cumulative effects of plastic damage. In response, this study introduces a novel macroscopic elastoplastic model grounded in plasticity theory, aimed at accurately characterizing the nonlinear behavior of stud connections subjected to concurrent shear and tensile forces. This paper meticulously delineates the implementation of the elastoplastic constitutive model using the backward Euler method for numerical integration. It further articulates the derivation of the consistent tangent stiffness, which aligns with the convergence efficiency of the Newton–Raphson iterative approach. The computation of the element stiffness matrix for a two-node element is executed via the governing equation inherent to the finite element method. An exemplar macroelement test conducted in ABAQUS affirms the implicit backward Euler scheme’s stability and consistency across varying tolerances. Validation of the elastoplastic model against empirical test outcomes corroborates its efficacy, demonstrating the model’s precision in predicting the load–displacement behavior of stud connections under the influence of shear and tensile forces.

Modeling and analysis of Double-Double composite structures integrating piezoelectric materials

Multifunctional materials and structures are increasingly important for innovative structural solutions. This work aims to model such structures constituted by Double-Double composites and piezoelectric materials. Besides the homogenization trend of these laminates as the number of the replicating sub-laminates grows, other features include simple ply drop placement, and card sliding to potentially save weight. To control the mechanical response, piezoelectrics along with several types of stacking were considered. The first-order shear deformation theory implemented via the finite element method was used to assess the model, and a set of verification and parametric studies was developed, resulting in a good performance confirmation.

An efficient model for 3D analysis of steel frames exposed to fire

The paper presents a nonlinear concentrated plasticity frame element for advanced analysis of steel frames exposed to elevated temperatures. The element extends the formulation based on the generalized plasticity material model that was successfully applied to the analysis of steel and composite structures. It considers the material's nonlinear behavior, temperature-induced loading, strength and stiffness degradation typical for structures under fire conditions. The nonlinear geometry is taken into account with the corotational formulation. Because of the generalized plasticity relations adoption, the element can describe the gradual yielding of cross sections. At the same time, the implemented return mapping algorithm ensures the element's high computational efficiency. The governing element equations, selection of parameters and computer implementation are discussed in the paper, followed by element validation through the number of experimental data examples and other numerical models. The comparative analysis demonstrated the element's versatility and capability to accurately predict the structural response of steel frame structures exposed to fire.