This paper, firstly, investigates the behavior of a pressure vessel designed based on the netting analysis method. Then, the strain measurement result performed to examine the behavior of the vessel ...is presented. It has been observed that the reverse strain is occurred at the joint of the vessel cylindrical area and its head. To inspect the experimental data, the ABAQUS software (finite-element) was deployed. The simulation results turned out to be in good consistency with the experimental data. Later, to design the vessel, Von Mises and Tsai Wu criterion were used for liner and composite layers, respectively. The design results showed that the netting analysis method is not optimal and leads to increase in the cost and weight of the vessel. In addition, investigating the vessel behavior indicated that using softer liner results in more exploit of the composite properties which in turn, can bring better performance in special applications. The good consistency between the experimental and simulation results proved that the complexity involved in the design of pressure metal-composite vessels can be greatly reduced through employing finite-element simulation methods.
•The different values of the coefficient F12 under different stress states were determined by using the basic strength values.•The improved Tsai–Wu criterion can distinguish the failure modes of ...composite materials.•The improved Tsai–Wu criterion has better prediction ability than the original, especially under the triaxial stress state.
Different failure modes are not explicitly accounted for in the Tsai–Wu failure criterion for composite materials, and the factor F12 in the expression cannot be determined by the basic strength values of the materials. In view of these two shortcomings of the Tsai–Wu criterion, an improved criterion was proposed based on the reasonable assumption that composites exhibit infinite strength under pure hydrostatic pressure. Some coefficients in the quadratic tensor expression of the Tsai–Wu failure criterion are redetermined using the basic strength value of the material, including the coefficient F12, under four different stress states (fiber tension and compression, matrix tension and compression). The reconstructed Tsai–Wu failure criterion can distinguish the failure modes based on different coefficient values under different stress states. In the progressive damage analysis of composite materials, the stiffness can be reduced in different manners based on each failure mode. Experimental verification for different kinds of unidirectional composites under various stress states was conducted, demonstrating that the improved Tsai–Wu failure criterion has a better prediction ability and accuracy than the original criterion.
This paper is to rationalise the empirical aspect of the Tsai-Wu failure criterion in the context of UD composites associated with the determination of the interactive strength property F12 based on ...the analytic geometry. It reveals that the condition of closed failure envelope cannot be satisfied by all UD composites and hence the restriction should be abandoned. Depending on the way the failure envelope opens, UD composites can be classified into two categories. (a) F12 can be determined uniquely using the conventional strength properties with an additional assumption that the material exhibits very high or infinite strength under triaxial compression at a specific stress ratio; or (b) The Tsai-Wu criterion leads to one of the two scenarios: either allowing infinite strength for an in-plane stress state or allowing infinite strength under triaxial stresses involving tension along fibres.
Several sectors have increased the use of lattice structures due its great capacity to reduce the structural mass with reasonable rigidity loss. However, these structures can present complex ...mechanical behaviors, impossible to be determined analytically. Surrogate models obtained from design of experiments have been shown to be promising but insufficient. Numerical models using finite elements are computationally expensive when optimization model updating is considered. In order to solve these problems, in this paper a deep learning model is trained in order to predict 16 different structural responses (static, dynamic and stability) of a complex composite isogrid structure tube. All input data were generated from a numerical finite element model. The results demonstrated substantial capacity of the deep learning model to fit the isogrid physical behavior and also predict the structural responses. In addition, it was also to predict the design parameters of the isogrid structure from the desired results, also demonstrating the good performance (R2 > 90 %) of the artificial intelligence model to perform this prediction.
Fiber-reinforced materials offer high stiffness- and strength-to-mass ratios to lightweight composite structures. To design stiff, strong, and lightweight fiber-reinforced composite structures, we ...propose a multimaterial anisotropic stress-constrained topology optimization framework that simultaneously optimizes geometry, distribution of anisotropic (i.e., orthotropic) and isotropic material phases, and local orientations of fiber reinforcements in the anisotropic phase. To achieve high performance in both stiffness and strength, we discover that both isotropic and anisotropic materials are needed: anisotropic materials are preferred in uniaxial members to increase stiffness, while isotropic materials are crucial at multi-axially stressed joints to enhance strength. We introduce multimaterial interpolation schemes to characterize both the stiffness and strength of composites made up of anisotropic and isotropic materials. The characterization of strength is enabled by a novel load factor-based yield function interpolation that consistently integrates anisotropic Tsai–Wu and isotropic von Mises yield criteria. We optimize stress-sensitive domains considering materials with various levels of stiffness and strength anisotropy as well as multiple load cases. The anisotropic stress constraints in the proposed framework effectively inform geometries to reduce stress concentration in fiber composites. The proposed framework provides a rational design paradigm for composite structures, capitalizing on dissimilar stiffness and strength properties of anisotropic and isotropic materials, to potentially benefit various engineering applications.
•Fiber composite topology optimization with anisotropic and isotropic yield criteria.•Stiff, strong, and lightweight composite design considering multiple load cases.•Consistent interpolation of Tsai–Wu and von Mises criteria using load factor.•Anisotropic stress constraints prevent yield failure in fiber-reinforced material.•Isotropic material strengthens multi-axially loaded fiber composite joints.
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•Strength of 370 MPa was obtained by tilting the beams from the lay-up configuration.•Tilted beams gave valid strength values even with a span-to-thickness ratio of 10.•Failure onset ...of 280 MPa was obtained through the maximum proportional limit stress.•Elastic constants and Tsai-Wu failure indices were predicted using material genome•UHTC enrichment did not affect strength and strain to failure (1%) of the well-developed SICARBON™.
Research efforts on Ceramic Matrix Composites (CMCs) are aimed to increase the operating temperature in oxidizing environments by adding Ultra-High Temperature Ceramic (UHTC) phases to the matrix. The structural performances of UHTC-enriched CMCs are generally investigated through bending test because it requires simple fixture and specimen geometry with small quantity of plate material. However, there are hardly any scientific studies which bring out what bending test conditions are required to determine reliable flexural strength of these composites. In this study, the effect of span length and specimen orientation on the flexural strength of UHTC-enriched SICARBON™ material, produced by Airbus, was comprehensively evaluated and reported. Transition of the failure mode was obtained by tilting the specimens with horizontal build direction instead of lay-up configuration (vertical build direction). The tilted configuration allowed to get a valid flexural strength of 370 MPa even with small specimens of about 30 mm. To assess failure mode in different test configurations, virtual microstructure was generated on the base of cumulative distribution functions of observed microstructural features. Tsai-Wu failure criterion was extended in order to evaluate direction dependent failure indices for different lay-up configurations.
Chopped carbon fiber sheet molding compound has a great potential in lightweight automotive, marine, and aerospace applications. One of the most challenging tasks is to predict the failure strength ...of the material due to its anisotropy and heterogeneity, as well as complex stress states in real-world working conditions. In this work, a novel constitutive model of carbon fiber chip is proposed to capture the pre- and post-failure behaviors under different loading modes. On this basis, we propose a new computational micromechanics model, which is calibrated and validated by uniaxial tensile, compressive, and in-plane shear experiments. Furthermore, a set of microstructures representative volume element (RVE) models under complex loading conditions are reconstructed to understand the relationship between the microstructure characteristics and the failure envelopes. Finally, several modified versions of classical failure criteria are proposed for anisotropic materials with consideration of the fiber orientation tensor. The modified Tsai-Wu failure criterion, which shows the best accuracy among all failure criteria, is highlighted in the comparative study.
The paper presents a numerical approach for the optimal design of any unidirectional fiber-reinforcement to improve the structural performance of existing structural elements. A problem of topology ...optimization is formulated, simultaneously searching for the regions to be strengthened and the optimal pointwise inclination of the reinforcement. Aim of the formulation is the minimization of the maximum equivalent stress in the underlying material, for a prescribed amount of fiber-reinforcement. The Tsai–Wu failure criterion is implemented to detect highly tensile-stressed regions in the existing structural components, both in case of isotropic material (e.g. concrete) and orthotropic media (e.g. brickwork or reinforced concrete). A suitable set of relaxed stress constraints is dealt with, calling for a no-compression stress state in the fiber-reinforcement. The resulting multi-constrained min–max problem is solved by mathematical programming. Numerical examples are presented to discuss the features of the achieved optimal layouts, along with their possible application as preliminary design for structural retrofitting. Performances of the adopted computational procedure are investigated as well.
In laminated composite materials design, optimization mainly targets the stacking sequence configuration, which is defined by the lamina thickness and fiber orientations within each layer. Recent ...studies emphasize the increasing role of Machine Learning in promoting innovative composite designs by facilitating the accurate modeling of essential properties such as strength and stiffness. This study introduces two metamodels that utilize feed-forward artificial neural networks, taking laminate thickness and fiber steering angles as input parameters. The output variables, including strain energy density and the Tsai-Wu failure index, enable the prediction of stacking sequence configurations for laminated materials, a capability confirmed in a case study. The results showcase neural network models with the ability to predict these variables, achieving coefficients of determination above 0.90 for testing data. Consequently, this modeling approach has the potential to be a tool for designers, aiding in decision-making processes for the subsequent optimization of stiffness and strength in structural components made of laminated composite materials.
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