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This paper experimentally and numerically investigates the failure behavior of plain woven composite-metal connection structures (T-joints) under loads in different directions. According to the direction of load application, it can be divided into TX specimens and TZ specimens. Wherein, TX and TZ are subjected to the tensile load parallel and perpendicular to the composite panel, respectively. Test results show significant differences in the ultimate load, failure modes and strain distribution among different specimens. Increasing the contact area between the lower block and the composite panel and adding round to the contact part between the metal part and the composite panel can improve the load-carrying capacity of the T-joints. The multiscale simulation is conducted to study the failure process of T-joints. Micro-scale and meso-scale models are established to obtain the mechanical properties of the plain woven composite, and the error between the simulated results and the experimental data is less than 10%. Progressive damage analysis is then done by using the macro-scale model. The simulated failure load and damage process of T-joints are consistent with the test results. The information and proposed multiscale analysis method on the failure behavior of T-joints are useful for the optimal design of similar structures. [ABSTRACT FROM AUTHOR]

To improve the simulation accuracy and evaluate the potential failure regions, this study proposes two finite element model correction methods based on surface manufacturing error: the direct numerical correction method and the deformation coordination correction method. Their methods aim to accurately describe the profile state of the composite antenna panel. The initial finite element model of prototype panel (Model IN) is respectively corrected by the direct numerical correction method (Model DN) and the deformation coordination correction method (Model DC). The prototype panel is then subjected to temperature difference testing. A comparison between the simulations and the test results reveals that Model DN and Model DC can predict the surface error distribution (SED) that Model IN lacks. The simulation results from Model DN and Model DC are overall consistent with the actual measurements obtained from the prototype panel tests. The average deviation of the simulated surface accuracy root mean square (rms) by Model DC from the test rms is only 1.66%, whereas that by Model DN is 19.44%. This demonstrates that the deformation coordination correction method effectively maintains simulation reliability in predicting antenna panel surface accuracy. Consequently, finite element model corrected by this method can provide valuable data support for evaluating the influence of potential failure regions and mitigating the impact on antenna surface accuracy. [ABSTRACT FROM AUTHOR]

To meet the strict new feature requirements for no-throwing parts and self-closing under bursting condition, a new composite cover is designed and analyzed experimentally and numerically. Test results show that the cover can be broken into 4 split subparts from the center to the flange by the warhead bursting, and the split subparts can be tied to the flange and automatic rebound and close after the missile is out of the launch container. Static finite element model under the pressure-bearing condition and dynamic finite element model under the warhead bursting condition are established. Numerical results, including processes of failure and self-close, are in good agreement with the experimental data. The influence of structural parameters such as the thickness of the main part of the cover and the number and the width of reinforcement layers, on the maximum deformation and the bursting failure load are investigated. The failure mechanism in the weak area and the automatic rebound and reset of the split subparts are also analyzed. [ABSTRACT FROM AUTHOR]

The general two-dimensional (2D) woven laminated composite (GWLC) is widely used in aviation, aerospace and high speed railways, and its superior specific stiffness and strength substantially reduce the weight of the structural components. However, when the GWLC is damaged by flexural, shear and impact loads, the layers are prone to delamination. To improve the interlayer properties of the GWLC, a loop warp yarn is added to the plain fabric by means of three-dimensional (3D) weaving technology, resulting in a double-side-loop fabric with Z-directional fibers. This paper investigates the double-notched shear (DNS) properties, in-plane shear properties, and flexural properties of GWLC and a new double-side-loop 2D woven laminated composite (DWLC). The test results verify that adding the loop warp yarns can greatly improve the interlayer properties of the general 2D woven laminated composites. The DWLC increases the interlaminar shear strength by 81.5%, the in-plane shear strength by 49.4%, and the flexural strength and modulus by 90.2% and 61.4%, respectively. The excellent mechanical properties of the DWLC lay a foundation for loop fabrics in engineering applications. [ABSTRACT FROM AUTHOR]

A new circular plate frangible composite cover was designed. The cover had a weak zone with embedded bonding structure to achieve the required one-way locking function. Eleven types of frangible covers with different structural parameters were fabricated by vacuum-assisted hand lay-up process. Experiments under bursting and external pressure loads were carried out. Both static and dynamic analyses were performed. The results showed that the frangible cover could achieve a high ratio of external to internal load-bearing limit under the premise of compact structure and small occupation. The ratio rose from 2.51 to 3.61 when the layer number of the separation part increased from 6 to 14. The ratio was 49.5% and 73.84% higher than the one of two types of cover reported in literature. Numerical results, including failure process, were in good agreement with the experimental ones. The influence of the parameters of embedded flange structures on the bursting failure load was also investigated. [ABSTRACT FROM AUTHOR]

Mapping an irregular domain into a square one is a common technique in analyzing problems of plates and shells with irregular shapes. For the irregular shape without four corners such as the elliptical shape, the difficulty arises that the Jacobian determinant is zero at the corner points. An efficient quadrature method is presented to analyze the transverse vibration of thin plates with an elliptical shape. To circumvent the above-mentioned difficulty, Gauss quadrature is used in numerical integration. Besides, derivative degrees of freedom are not used, and a boundary point is modeled by two nodes separated by a very small distance. Since the nodes are not coinciding with integration points, a way indirectly using the differential quadrature law is employed to derive the explicit formulas to ease the programming. A convergence study is performed. Free vibration of elliptical plates with continuous and discontinuous edge conditions is analyzed to demonstrate the efficiency of the developed rotation-free weak-form quadrature method. [ABSTRACT FROM AUTHOR]

We propose a modified Laurent series for investigating the elastic field around holes/inclusions under plane deformation by dividing the classical Laurent series over the first derivative of the conformal mapping, which is justified from a mathematical point of view. Through a group of numerical examples concerning the stress concentration around holes of common shapes, the accuracy of the modified Laurent series is verified. It is also demonstrated that the use of the modified Laurent series as compared with the classical one generally leads to significantly more accurate results with even much fewer terms of the series. Utilizing the modified Laurent series, we revisit the stress field around an irregularly shaped elastic inclusion embedded in an infinite matrix and effectively eliminate the severe interfacial stress fluctuation reported earlier in the literature. More importantly, the modified Laurent series may be very useful for a highly accurate prediction of the physical field in particulate composites with densely packed inclusions. [ABSTRACT FROM AUTHOR]

Transverse mechanical properties play an important role in the study of fiber reinforced composite materials. An experimental and numerical study on mechanical properties and damage behavior of unidirectional fiber reinforced composites under transverse load is presented. The quasi-static tensile and compressive tests were carried out to obtain mechanical properties of unidirectional fiber reinforced composites under transverse tension and compression. The fracture morphologies of the specimens were observed by scanning electron microscopy (SEM) to reveal their distinct damage mechanism. Considering the effects of interface, a new interfacial model is proposed. Two representative volume elements (RVEs) of basic and interfacial models are established for comparison analysis. The predicted results agree well with the experimental data. The introduction of interfacial layer has little effect on the prediction of transverse modulus, but can improve the accuracy of the predicted transverse strength. The fiber volume fraction has a great influence on the transverse mechanical properties of unidirectional fiber reinforced composites. As the fiber volume fraction increases, its transverse modulus increases, but both the transverse strength and the ultimate strain decrease. [ABSTRACT FROM AUTHOR]

Tensile properties and failure mechanism of 3D woven hollow integrated sandwich composites are investigated experimentally, theoretically and numerically in this paper. Firstly, the tensile properties are obtained by quasi-static tensile tests on the specimens in two principal directions of the sandwich panels, called warp and weft. The experimental results shows that the tensile performances of the warp are better than that of the weft. By observing the broken specimens, it is found that the touch parts between yarns are the main failure regions under tension. Then, a theoretical method is developed to predict the tensile properties. By comparing with the experimental data, the accuracy of the theoretical method is verified. Simultaneously, a finite element model is established to predict the tensile behavior of the composites. The numerical results agree well with the experimental data. Moreover, the simulated progressive damages show that the contact regions in the warp and weft tension are both the initial failure areas. [ABSTRACT FROM AUTHOR]

The structural behavior and damage propagation of 3D woven composite stiffened panels with different woven patterns under axial-compression are here investigated. The panel is 2.5D interlock woven composites (2.5DIWC), while the straight-stiffeners are 3D woven orthogonal composites (3DWOC). They are coupled together with the Z-fibers from the stiffener passing straight thought the thickness of the panel. A 'T-shape' model, in which the fiber bundle structure and resin matrix are drawn out to simulate the real situation of the connection area, is established to predict elastic constants and strength of the connection region. Based on Hashin failure criterion, a progressive damage model is carried out to simulate the compressive behavior of the stiffened panel. The 3D woven composite stiffened panels are manufactured using RTM process and then tested. A good agreement between experimental results and numerical predicted values for the compressive failure load is obtained. From initial damage to final collapse, the panel and stiffeners will not separate each other in the connection region. The main failure mode of 3D woven composite stiffened panels is compressive failure of fiber near the loading end corner. [ABSTRACT FROM AUTHOR]

An experimental, theoretical and numerical investigation on the shear behavior of 3D woven hollow integrated sandwich composites was presented in this paper. The microstructure of the composites was studied, then the shear modulus and load-deflection curves were obtained by double lap shear tests on the specimens in two principal directions of the sandwich panels, called warp and weft. The experimental results showed that the shear modulus of the warp was higher than that of the weft and the failure occurred in the roots of piles. A finite element model was established to predict the shear behavior of the composites. The simulated results agreed well with the experimental data. Simultaneously, a theoretical method was developed to predict the shear modulus. By comparing with the experimental data, the accuracy of the theoretical method was verified. The influence of structural parameters on shear modulus was also discussed. The higher yarn number, yarn density and dip angle of the piles could all improve the shear modulus of 3D woven hollow integrated sandwich composites at different levels, while the increasing height would decrease the shear modulus. [ABSTRACT FROM AUTHOR]

Tensile properties and failure mechanism of a newly developed three-dimensional (3D) woven composite material named 3D nonorthogonal woven composite are investigated in this paper. The microstructure of the composite is studied and the tensile properties are obtained by quasi-static tensile tests. The failure mechanism of specimen is discussed based on observation of the fracture surfaces via electron microscope. It is found that the specimens always split along the oblique yarns and produce typical v-shaped fracture surfaces. The representative volume cell (RVC) is established based on the microstructure. A finite element analysis is conducted with periodical boundary conditions. The finite element simulation results agree well with the experimental data. By analyzing deformation and stress distribution under different loading conditions, it is demonstrated that finite element model based on RVC is valid in predicting tensile properties of 3D nonorthogonal woven composites. Stress distribution shows that the oblique yarns and warp yarns oriented along the x direction carry primary load under x tension and that warp yarns bear primary load under y tension. [ABSTRACT FROM AUTHOR]

A lightweight and auto-separated canister cover is required for quick launching in some specific missile launchers. In this paper, a new frangible composite canister cover with the function of specified direction separation is proposed and studied via both experimental and numerical approaches. The frangible canister cover with local non-split weak zone structure, which is manufactured by traditional hand lay-up process with vacuum assisted resin infusion (VARI) method, is designed to fail and separate in a predetermined and specified direction in comparison with the cover with full split weak zone structure. This design is innovative and also necessary for reduction of potential risk to peripheral equipment around the missile launcher. The failure pressure of the cover is determined on the basis of the failure criteria used in finite element (FE) model. In experimental pressurized testing, a number of frangible canister covers subjected to pressure loadings in six cases are studied. Close agreements between the experimental and numerical results have been examined. The frangible canister covers with local non-split weak zone structure which have been studied can be separated and fly out to the specified direction. [ABSTRACT FROM AUTHOR]