Three-Dimensional Bending Analysis of Multi-Layered Orthotropic Plates by Two-Dimensional Numerical Model

The paper presents effective numerical modelling of multi-layered plates with orthotropic properties. The method called the FEM23 is employed to construct the numerical model. The approach enables a full 3D analysis to be performed while using a 2D finite element mesh. The numerical model for a multi-layered plate is constructed by an assembling procedure, where each layer with orthotropic properties is added to the global numerical model. The paper demonstrates that the FEM23 method is very flexible in defining the multilayered plate, where the thickness of each layer as well as its mechanical orthotropic properties can be defined independently. Several examples of three-layered or nine-layered plates are analyzed in this paper. The results obtained by the FEM23 method coincide with the ones taken from the published papers or calculated with the standard 3D FEM approach. The orthotropic version of the FEM23 can be quite easily applied for other kinds of problems including thermo-mechanics, free vibrations, buckling analysis, or delamination.

An approach to adhesive bond characterisation using guided acoustic waves in multi-layered plates

An approach for the non-destructive characterisation of adhesive bonds using guided ultrasonic waves is presented. Pulsed laser radiation is used to thermoacoustically excite broadband ultrasonic waves in a multi-layered sample, consisting of a metal plate adhesively joined to a polymeric layer using synthetic resin. The resulting signals are received by a purpose-built piezoelectric transducer. Varying the distance between excitation and detection yields spatio-temporal measurement data, from which the dispersive properties of the propagating waves can be inferred using a two-dimensional Fourier transform, assuming the plates to act as coupled waveguides. Coupled multi-layered waveguides show an effect referred to as mode repulsion, where the distance between certain modes in the frequency-wavenumber domain is assumed to be a measure of coupling strength. Measurements at different stages of curing of the adhesive layer are performed and evaluated. A comparison of the results shows changes in the dispersive properties, namely an increased modal bandwidth for the fully cured sample as well as an increased modal distance.

Maximum permissible inelastic deformations of hybrid rectangular plates during intense explosions

Для гибридных прямоугольных слоистых пластин из произвольных наборов изотропных конструкционных материалов с симметричной структурой расположения слоев относительно отчетной (нейтральной) поверхности получены аналитические формулы оценок допустимой остаточной повреждаемости при воздействии интенсивных нагрузок взрывного типа. Закрепления контура предусматривают любую комбинацию из жестких или шарнирных условий отдельных сторон прямоугольного контура. В основе рассмотренной модели использованы традиционные кинематические гипотезы Кирхгофа, деформационная теория А.А. Ильюшина, принцип слабейшего звена для используемых материалов и деформационный критерий предразрушения для всех используемых фазовых материалов. Использован наиболее распространенный в практике закон изменения во времени давления на фронте взрывной волны. For hybrid rectangular layered plates from arbitrary sets of isotropic structural materials with a symmetric structure of the arrangement of layers relative to the reporting (neutral) surface, analytical formulas for assessing the permissible residual damage under the action of intense explosive loads are obtained. Contour anchors provide for any combination of rigid or hinge conditions of individual sides of a rectangular contour. The considered model is based on the traditional kinematic hypotheses of Kirchhoff, the deformation theory A.A. Ilyushin, the principle of the weakest link for the materials used and the deformation criterion for pre-fracture for all used phase materials. The most widespread law of time variation of pressure at the front of a blast wave is used.