Search

• The low-restraint GLARE is taken as a research object and its deformation characteristics and failure mode are studied using uniaxial tensile, bending experiments and numerical simulation in this paper. • Based on experimental observations, it is found that the low-restraint GLARE produces the phenomenon of interlayer slip, and the interlaminar residual stress is much smaller than the cured laminate, whereas the deformation limit and performance are improved. • The results of bending experiments revealed that the load variation of low-restraint laminate is significantly different from the cured laminate during bending. • The low-restraint GLARE does not obviously delaminate and fracture during bending due to the low interlayer residual stress and a certain degree of interlayer slipping, exhibiting a significant improvement in the bending forming limit. • This paper provides theoretical bases for the in-depth analysis of deformation properties and forming laws of low-restraint GLARE, guiding further applications of laminates. Fiber metal laminates (FMLs) possess a better weight reduction effect than traditional metal materials due to the coupling properties of heterogeneous materials, showing promise in the areas of aviation and aerospace. At present, the research on FMLs mainly focuses on the deformation properties after curing while the mechanical properties in the low-restraint state, i.e. the laminates are temporarily not cured and are formed under lower constraint stresses, are not studied in detail. Herein, the low-restraint GLARE is taken as a research object and its deformation characteristics and failure mode are studied using uniaxial tensile, bending experiments and numerical simulation in this paper. Moreover, the influence of key parameters, such as temperature, laminate structure and span length, is investigated, as well as the tensile and bending deformation behavior of GLARE in a low-restraint state is obtained. In addition, based on experimental observations, it is found that the low-restraint GLARE produces the phenomenon of interlayer slip, and the interlaminar residual stress is much smaller than the cured laminate, whereas the deformation limit and performance are improved. This paper provides theoretical bases for the in-depth analysis of deformation properties and forming laws of low-restraint GLARE, guiding further applications of laminates. [ABSTRACT FROM AUTHOR]

• A novel non-linear numerical model for thin-walled members is presented. • Four classes of H-section members are selected to study the hysteretic behaviour. • The comparison of test results and those of the proposed model is accomplished. • The deformation mode, buckling effects, and material nonlinearity are considered. Based on Gonçalves's geometrically exact beam theory considering cross-section deformation, the warping and distortional deformation of thin-walled members are described in this paper by means of a combination of section deformation modes. By integrating with the J2 elastic‒plasticity theory for the steel, a numerical model is established for the hysteretic behaviour of thin-walled steel members. Four classes of H-section members are selected on account of the design codes, and the influence of section warping and distortion deformation modes on the calculation of the hysteretic behaviour of components with different section types is analysed. The crucial aspect lies in the bending hysteresis behaviour around the strong and weak axes of the cross-section for H-beam steel members subjected to typical thin-walled members with relatively large widths and thicknesses. Test results on the hysteretic behaviour of H-section steel members are compared with those calculated from the proposed model in terms of the hysteric behaviour of components, strength degradation, energy-dissipating capacity, etc. These findings validate the correctness and feasibility of the established non-linear analysis model for thin-walled members. [ABSTRACT FROM AUTHOR]

• The rapid maximum dynamic stress (S max) prediction method of Miura-ori core sandwich panels with impact defects is proposed, which could directly predict S max with few simulations by establishing the relationship with impact deformation in advance. • S max of sandwich panels will increase by 2.635 times with the impact deformation below 32.1 % of Miura cell projection area. • The impact deformation is predicted by the geometric relationship of Miura creases and material properties, and the prediction errors are below 12.5 %. Miura-ori core sandwich panels have great application potential in aviation aircraft. Subject to the impact and vibration loads, the small impact defect will increase the dynamic stress, resulting in fatigue failure. Moreover, the Miura creases complicate the impact deformation, which is extremely time-consuming to analysis the dynamic stress only through simulation. Therefore, a rapid dynamic stress prediction method for Miura-ori core sandwich panels is first proposed based on the predicted impact deformation by arbitrary defects in this paper. The dynamic stress of sandwich panels could be directly calculated with few numerical results by establishing the relationship with impact deformation in advance. The vibration mechanism of sandwich panels with defects is revealed. Although the deformation area is below 32.1 % of Miura cell projection area, the dynamic stress will increase by 1.984–2.635 times with different defects. The impact deformation is predicted by the geometric relationship of Miura creases and material properties, and the prediction errors of hemispherical and drilling defects with arbitrary defect positions are below 12.5 % and 10.6 %, respectively. Taking two types of defects (hemispherical and drilling defects), different defect depths and positions into consideration, the prediction errors of maximum dynamic stress are from -7.9 % to 16.8 % compared to simulation. [ABSTRACT FROM AUTHOR]

• The bi-modular FGMs UMAT is developed for the first time and successfully conducted to validate the perturbation solution. • The rise-to-thickness ratio and corresponding critical load are two factors influencing the snap-through buckling. • The rotation constraint and radial constraint at the shell edge have opposite effects on the snap-through buckling. • The bi-modular FGM effect may speed up or slow down the snap-through buckling. Functionally graded materials (FGMs) enable structures to achieve a smooth transition between different material properties, providing an optimized combination of functions to meet the diversity of engineering needs. However, the presence of bi-modular effect in FGMs is often neglected due to the complexity in the analysis. In this paper, the curvature correction equivalent method based on the von Kármán theory will be applied to the theoretical study for the large deformation problem and the resulting snap-through buckling of functionally graded revolutionary shallow thin shells with bi-modular effect under different boundary constraints. Furthermore, a bi-modular FGMs user material subroutine (UMAT) is developed for the first time to simulate the real material model, thus validating the theoretical solution. The results show that except for the bi-modular effect of materials, boundary constraints of shells also have important influences on the relationship of load vs. central deflection and snap-through buckling. The research of boundary constraints brings new conclusions to snap-through buckling: the rotation constraint and radial constraint at the shell edge have opposite effects on snap-through buckling. This work will contribute to the analysis of the snap-through buckling of functionally graded revolutionary shallow thin shells with an obvious bi-modular effect and under various boundary constraints. [ABSTRACT FROM AUTHOR]