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This paper is focused on description of the mechanical response of the aluminum box-beams subjected to 3 point bending (3-PB). The main aim of this paper is to determine the effect of spacing between rivets on the equivalent stiffness and strength of the analised profile. The considered beams are composed of two sections: one of them is an aluminum omega profile and another is a composite flat sheet. Experimental tests were carried out for various spacing between rivets. Moreover, the corresponding numerical analyses by Finite Element Analysis (FEA) with application of the Abaqus software were done for estimate of the mechanical response of the box beams. The results show relationship between spacing of the rivets and values of carrying forces.

While the plane is maneuvering before start or landing, some solid particles (e.g. sand, dust, soil) can be sucked into an engine with the air. Their vast majority is stopped on the compressor blades, but the smaller ones are able to get into a hot part of the engine and cause erosion. Erosion is widely recognized as the second mechanism, after corrosion that reduces the TBC coating thickness. In many cases, erosion can completely remove it. Furthermore, TBC coatings are more susceptible to erosion due to their porous structure than full dense ceramic materials. In order to investigate the phenomenon of particles impact with diameter of 4mm, the pneumatic driven laboratory work station was built. The work station has an adjustable pressure, so that the foreign object may possess different kinetic energies. The pressure can be read on a digital pressure gauge and the shot release is done electrically. In addition, the work station has a universal cross table that provides precise positioning of the sample so as to be able to perform a dozen or so impacts in predetermined distance intervals. However, the most important component is the velocity measurement system which is used to determine the impact energy. The paper presents the results of 11 impacts made with different energies. The effect of complete destruction of the ceramic layer as well as indents without visible damage was achieved. Numerical simulations allowed to define the zones of stress influence of the individual indents. The brittle cracking model in Abaqus allowed the virtual representation of damage due to impact load.

This paper presents the results of Mode I fracture toughness tests of concrete with fly ash (FA) loaded in Mode I. Concrete composites with the addition of 0%, 20% and 30% siliceous FA were analysed. Fracture toughness tests were performed on a MTS 810 testing machine. The studies examined the effect of FA additive on the quasi-static fracture toughness KIcS. The analysis of the results revealed that a 20% FA additive causes an increase of KIcS value, while a 30% FA additive causes a decrease on fracture toughness. Additionally, the results demonstrate the possibilities of practical application of ARAMIS system for analysing the development of defects in the micro-structure of concretes containing FA additives. This system can be useful for macroscopic estimation of crack propagation.

In the jet engine the temperature of exhaust gases should be as high as possible, from the point of view of its efficiency. The value of this temperature is limited by toughness of the turbine blades material. Superalloy Inconel 625, which is commonly used in aerospace industry, indicates 13% less yield point in 800OC than in 25OC. The temperature of exhaust gases can reach 1500OC. The blade material has to be protected due to this fact. The one possibility of turbine blade protection is using of thermal barriers coatings (TBC). The coating has a very low thermal conductivity and therefore it protects against the thermal shock failure of the substrate material. The TBC can be manufactured as: 1) monocrystalline, 2) layered structures (e.g. [1-3]) or 3) as a functionally graded material (e.g. [4-7]). The differences between the properties of blade material and TBC can lead to significant increase of the high shear stresses in the substrate-TBC interface.In this paper numerical analyses of cooled turbine blade with various kinds of functionally graded thermal coatings were performed. The main aim was to find the optimal material properties distribution of the functionally graded TBC to avoid damage initiation and growth between TBC and substrate. In the calculations the effect of temperature on material properties both mechanical and thermal was taken into consideration.

A description of processes of formation and propagation of cracks in material requires the knowledge of all fracture mechanics parameters, i.e.: KIc, KIIc and KIIIc. In this study a new testing method and estimation of the fracture toughness in Mode III (antiplane shear) of concretes containing: 0, 20 and 30% volume content of the class F fly ash (FA) was proposed. Fracture toughness tests were performed on axial torsion machine MTS 809 Axial/Torsional Test System. The studies examined effect of FA additive on the parameter KIIIc. In order to determine the fracture toughness KIIIc a special device was made. Experimental investigation under third mode fracture was carried out both in young and mature concrete composites (after: 3, 7, 28, 90, 180 and 365 days). 20% addition of FA as well as a 30% addition of FA causes a reduction in fracture toughness of young concrete. After 28 days of couring a significant increase of the KIIIc was noticed in composites with a 20% additive of FA while concrete mixtures with a higher additive of FA still had lower analyzed fracture mechanics parameter.

Indentation in brittle solids involves many complex phenomena related to cleavage and contact, as well as intrinsic stress singularities, which are almost impossible to capture with traditional continuum approach and FEA at mesoscale. In case of a two-phase ceramic composite [1–3] the number of unknown material and interfacial constants, that have to be calibrated experimentally, increases rapidly [4, 5]. In this paper, nanoindentation in zirconia-toughened alumina (ZTA) is modelled using discrete (peridynamical) approach

Different types of techniques are used in joining of aircraft structures. The classical solutions are mechanical or bonding joining. A prospective alternative to the currently used connections (e.g. mechanical, adhesive and hybrid ones) is a socket - pin connection type. Generally, they are purely mechanical joints. Depending on the shape, they have different commercial names such as: Interlock, Snaplock, Snapfit Gridlock. The idea of these connections relies on the fact, that between the socket and the pin we need a suitable interference fit or specially formed clip to carry the load. The advantages of this type of connection of different structural parts is very fast assembly after pressing joined parts together. The use of socket - pin connection eliminates the presence of the human error and reduces production costs as an individual connection is made by CNC machine tools.The paper presents an analysis of the influence of a several technological problems concerning the socket and the pin manufacturing, on the value of force required for the joint connection and disconnection. A number of numerical simulations was made in ABAQUS program to examine the effect of such parameters as: the presence of interference fit, the use of spherical latches, the use of different rigidity in the shaft by making cuts with variable width and length, the use of different angles of inclination of the working part of the slot.

The heat transfer problem in the 2-phase composite material containing metallic and elastic phases, subjected to quick temperature variations, is the aim of theoretical analysis. The full description of the composite behaviour starts from the formulation of governing equations at 2-scale levels: micro-and macro-, passes through specification of the internal structure of the composite and finishes by numerical solution of the heat transfer problem through the considered material sample. The most important in the analysis are thermo-mechanical properties of the composite components creating the material. The big difference of the both phases properties (mismatch) can create additional difficulty in the exact thermal description of the composite. It is necessary also to specify by scanning electron microscopy (SEM) observations a real material internal structure, which includes: grain shapes and matrix, to create of the proper size of the Representative Volume Element (RVE) for numerical calculations.In the numerical example we analyse cermet, i.e. the composite build up of metallic matrix (cobalt) and tungsten carbide elastic grains, which exhibits high brittleness. Heat transfer across this very complex material causes heat flux concentrations in the metallic phase and further stress concentrations. These concentrations act as sources of damage initiators at the binder/carbide grains interfaces. The obtained results lead to the conclusion that the spatial distribution and content of the metallic phase first of all influence the heat transfer across the 2-phase composites.

Waste tires create big problem in the world as for their utilization. One domain in which this material is able to found promising application is civil engineering. The waste tires additive in the concrete manufacturing leads to change of mechanical properties such as: Young modulus, compressive strength, fracture toughness, energy absorption, brittleness, water absorption etc. It was partly reported in the literature only for the plain concrete. There is no investigations for a lean concrete - the material which has potential applications as a subgrade of roads. The aim of this paper is to investigate the importance of the rubber particles addition in the lean concrete production as for modification of the basic mechanical properties and further degradation of the material due to mechanical loading. The new technology of compaction of the concrete was elaborated to perform basic test: cyclic uniaxial compression and cyclic bending. In order to describe gradual degradation of the rubberized lean concrete a scalar damage parameter D related to loading history was proposed. The current value of the elastic modulus was expressed as E=Eo(1-D), where Eo denotes the initial value of the Young’s modulus. The paper includes also a numerical model of the beam made of the rubberized lean concrete, which is subjected to 3-point bending deformation. The stress distribution in this beam is highly non-homogeneous with visible stress concentrations around the rubber particles.

Thermal Barrier Coatings (TBCs) have been extensively used in aircraft engines to improve durability and performance. They protect critical engine parts such as blades and combustion chambers, which are exposed to high temperatures and corrosive environment.Testing of coated metallic alloys, subjected to ageing process, allows determination of the TBCs properties. In this paper we performed 2 tests: uniaxial tension and bending. The aging of samples was carried out in 1000°C for times: 48h, 89h, 185h and 353h. Thermally Grown Oxide (TGO) layer thickness (SEM observations) and the strain level corresponding to damage of the TBCs were determined experimentally.The experimental results were used to build numerical model in Abaqus program. Brittle cracking damage model was applied to describe of the TBC layer degradation. Surface based cohesive behavior was used to model delamination of the interface between a bond coat (BC) and a top coat (TC).The proposed numerical model describes with high accuracy experimental results.

Cellular materials represent a new class of materials; main parameters that characterize the cellular structure are relative density, shape of the cell (open or closed), wall thickness and cell diameter. The purpose of this paper is to investigate the microstructure of foams materials and also to determine the flexural properties of this rigid PUR foams using Digital Image Correlation (DIC). The rigid PUR foams cells morphology and pore distribution for three densities (100, 145 and 300 kg/m3) were studied before testing through scanning electron microscopy. Determination of flexural properties was carried out on rectangular beam samples using ARAMIS 2D system. This method provides a substantial increase in accuracy for measuring strain and is based on the calculation of surface deformation using a set of digital images from undeformed stage to different deformed stages. The specimens were subjected to static three points bending tests with loading rate of 2 mm/min, at room temperature and loading was applied in rise direction of the foam. Experimental results show that main mechanical properties such as flexural modulus and flexural strength values increases with increasing of density.

Adhesive bonding of two different materials appears in many modern engineering applications, e.g.: airplanes, boats, cars etc. In many practical problems the adhesive bonding is subjected to shear loading. Therefore this is important to investigate the whole deformation process of the considered type of joints under monotonic loading, to get information about the shear strength and strain concentrations. Such concentrations lead to microdefects initiation and their further coalescence to create a main crack. The unstable crack propagation leads to final failure of the adhesive joint. The Digital Image Correlation (DIC) System - ARAMIS allows for constant monitoring of the deformation state up to the final failure. The tests were performed for bi-material specimens made of adhesively bonded PMMA and aluminum strips (Fig.1) and for pure PMMA and pure aluminum specimens. Additionally, two strain gauges on each homogeneous specimen and four on the bimaterial ones are used for strains estimations. The four point bending Iosipescu tests were performed using MTS machine with constant speed. In the first method (DIC) the ARAMIS system recorded a displacement distribution in samples with frequency 1Hz. In the second method the strains were recorded by the strain gauges - using analog output channels of the HOTTINGER data Acquisition System - MGCPlus, the current value of the load using analog output channel of the MTS machine was recorded too. The load-displacement curves were obtained for the whole deformation process and the shear strength of the joints was estimated. The energy absorption of the joints was calculated.

This paper presents the size effect on fracture toughness of polyurethane foams (PUR 40), with nominal density 40 kg/m3, closed-cell rigid foams widely used for sandwich cores. Determination of the fracture toughness was carried out by three-point bending tests (TPB), on notched specimens, at room temperature (20±2ºC). To determine the size effect in Mode I fracture toughness, specimens geometrically similar in two dimensions with length-to-width ratio 5:2 were selected. The specimens were subjected to a quasi-static loading with a speed of 2 mm/min, which was applied exactly on the notch direction. A strong size effect in the closed-cell PUR foam is experimentally demonstrated, by considering a smooth transition between strength of materials approach (with no size effect) and asymptotic case of linear elastic fracture mechanics.

Mode II fracture analysis is especially important. This mode is vital in relation to concrete, due to its relatively low shearing strength and high sensitivity to such type of stress. Nowadays, the structural concretes containing an additives of fly-ash are quite commonly used in the construction industry. Initial cracks origin and development research was carried out using samples for three concrete mixtures: concrete without silica fly-ash (FA), concrete with 20% and concrete with 30% FA additive. 150x150x150 concrete cube with two initial cracks was used as a test sample. Experimental investigation under Mode II fracture was carried out in concrete composites at early age (after 3, 7, 14 and 21 days). X-FEM method enables observation of defect initiation and development, there is no need to input the original conditions. Calculations used peak principal stress criterion. Most calculations coincide with results of experimental research. There was a convergence of: cracks shapes, FQ critical force values, force - displacement graphs.