Instytut Podstawowych Problemów Techniki

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A continuum model of a moving transition layer separating two different solid phases of a certain micro-damaged material is proposed. An application of this model to the analysis of the propagation of this layer in a micro-cracked solid is shown.

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The aim of the contribution is to formulate an engineering theory describing the dynamic behaviour of periodically waved shell-like elements, called wavy plates. On the basis of the proposed theory, the effect of coupling between free macro- and micro-vibrations of a wavy plate is investigated. It is also shown that the homogenized model of wavy plates (obtained by scaling down the wavelength parameters) cannot be applied in the analysis of dynamic problems.

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In this contribution an averaged refined model of a rigid heat conductor with micro-periodic structure is formulated. The proposed model describes the effect of a microstructure length dimension on the time-dependent heat transfer processes. It is shown that this effect plays a crucial role in the analysis of nonstationary problems and hence the known effective modulus theories of heat conduction (where the microstructure is scaled down), have the range of applicability restricted to steady-state problems.

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The subject of the contribution is an investigation of elastic composite plates with a microperiodic structure along the plate's midsurface. The computational models of the plates are largely based on the homogenization procedures leading to equations with constant coefficients. However, the homogenization theories neglect the microstructure length-scale effect on the plate's dynamic behaviour. The objective of this research is to formulate and investigate a refined theory of the composite plates under consideration, which would describe the microdynamic plate behaviour caused by the microstructure. The possible applications of the proposed theory are shown by an example.

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The objective of the paper is to propose a simple method of formulation of 2D-theories for composite thin plates made of an arbitrary inhomogeneous linear-elastic material. The effect of inhomogeneity on the plate stiffness will be described by means of extra unknowns, called correctors, which have to satisfy a system of linear algebraic equations. The elimination of correctors can be performed in explicit form and leads to the formulas for effective stiffnesses of the plates under consideration.

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The effect of interlaminar bonding imperfections on behaviour of shells, investigated in [1], is elaborated here for a special case of laminated plates. The problem is stated for linear elastic materials, within the small displacement gradient theory. The obtained results are ilustrated by an example.

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In this contribution the effect of interlaminar initial imperfections on a composite shell behavior is investigated. The constitutive equations for shells with initial interlaminar bonding imperfections are obtained.

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The chaotic distributions of delaminated surface elements in laminates are described by a macrodelamination density function. Using this concept a phenomenological discrete mathematical model of the interlaminar debonding processes is proposed. For multilayered periodic composites the discrete model is approximated by a certain continuum model of delamination processes.

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In the paper it is shown how to formulate certain homogenized models of thermoelastic-unelastic periodic composites under large strains and large temperature gradients. The models obtained describe local stresses and heat fluxes in every material component in term of averaged displacement and temperature fields and certain extra unknowns called microlocal parameters.

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