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World War I proved air forces to be a critical driver for warfare outcomes. Mastery of the latest technology appeared to be crucial to the battle’s success. The combat capabilities of airplanes improved manifold due to the increased power of aircraft engines, thus initiating a new era in aeronautics. By July 1917, the aviation of the Russian Empire included 91 air squadrons and 5 units of heavy multi-engine aircraft known as Ilya Muromets. Several enterprises, including the town of Aleksandrovsk, were manufacturing engines for these planes. The origin of engine production in Aleksandrovsk was associated with the establishment of a branch of Petrograd Joint Stock Company of Electromechanical Structures called Deka. The article aims at analyzing the prerequisites and conditions for the foundation of an aircraft engine enterprise in Ukraine. While drafting the article, the authors relied on chronological, historiographical, and other historical methods of research, which have been widely used both in considering the contribution and influence of certain individuals and reviewing the stages of creation and development of separate enterprises, as well as specific industries. Based on the retrospective analysis, the prerequisites and conditions of the foundation of the aircraft engine enterprise in Aleksandrovsk, Ukraine, were considered. There was a severe gap between the Russian Empire and European countries in the development pace of the aviation industry during World War I. This prompted the Russian Empire to raise foreign capital, as well as attract technologies and specialists to develop aircraft engineering and other industries. By 1917, the plant had gained the status of Russia’s largest engine-building enterprise in terms of building area and one of the best in equipment. It is evident that the beginning of aircraft engine production in Aleksandrovsk relates to the establishment of a branch of Petrograd Joint Stock Company of Electromechanical Structures and the plant’s purchase from the Moznaim brothers.

An obligatory condition for creating a competitive aircraft (AC) is to ensure low operating costs by reducing downtime and rational organization of maintenance and repair through continuous monitoring, diagnosis, and prediction of the AC condition. For monitoring, diagnosing, and predicting aircraft condition in recent decades the list of parameters recorded on board is continuously expanding. Great prospects in this direction are associated with the creation and implementation of so-called smart materials that can monitor their condition and even actively resist damage. This article presents results of research showing the fundamental possibility of constructing a strain curve for structural metal based on hardness measurement by ultrasonic contact impedance. During performance of experiments on aluminium alloy AMg6 samples a correlation relationship is established for strength properties obtained on the basis of a stress-strain curve with hardness values during tests that make it possible to evaluate material condition with a complex stress-strained state. Implementation of this approach demonstrates the expediency of predicting the current mechanical condition and residual life of metal structures based on analysis of dynamics of the change in structural material hardness parameters. [ABSTRACT FROM AUTHOR]

Trajectory similarity-based prediction (TSBP) is an emerging real-time remaining useful life (RUL) prediction method that has drawn considerable attention in the field of data-driven prognostics. TSBP is fast, and the corresponding model is easy to train. However, TBSP only provides a point estimation of RUL, which is insufficient for some specific prognostic applications. Hence, this study introduces an improved TSBP method to handle the issue of prognostic uncertainty. On the basis of an adaptive kernel density estimation technique and β-criterion, the improved TSBP method not only provides an accurate and precise point prediction of RUL but also specifies the confidence interval of RUL prediction. The capability of obtaining the confidence interval of RUL can enhance the TSBP method for uncertainty management. The effectiveness of the proposed method is validated through two cases studies, which are related to turbofan engine prognostics. [ABSTRACT FROM AUTHOR]

The aim of this work is the experimental investigation of fatigue failure in Refill Friction Stir Spot Welding joints. The specimens for the fatigue analysis were made of 0.8-mm-thick and 1.6-mm-thick 7075-T6 aluminium alloy which is used to fabricate aircraft fuselages consisting of a plate skin with a stiffening stringer. The load capacity of joints was determined by tensile/shear tests. Fatigue tests were carried out on an Instron E10000 testing machine at room temperature. High-cycle fatigue tests were carried out under the following conditions: a limited number of cycles equal to 2 × 106, a frequency of 50 (Hz), and a coefficient of stress cycle R = 0.1. Microstructural features of fatigue fractures for different levels of variable load were examined using Scanning Electron Microscopy micrographs. The analysis of the fatigue fractures reveals that the Alclad layer at the bottom of the weld is a kind of structural notch and in this situation can be the location of the initiation of fatigue cracking. It was found that fracture mechanism depends on the value of load amplitude. Analysis of the SEM micrographs of fatigue fractures shown that the thermo-mechanically affected zone and heat affected zone are sources of fatigue failure. [ABSTRACT FROM AUTHOR]

Formulation of the problem. The Civil Aviation of Ukraine plays a significant role in the Ukrainian society and in the international arena. It performs multifaceted functions - passenger and cargo transportation, conducting aviation works in agrarian and forestry farms, providing medical aid, performing search and rescue operations, fire fighting, construction works, cultural and sporting events, scientific research, etc. Currently, an objective study of the aviation industry is relevant, especially since there are some problems that create a negative impression of Ukrainian aviation and the perception of its decline in modern conditions. Goal. To analyze the activity of civil aviation of Ukraine from the beginning of the 21st century to the present and, using the problem-chronological method, to comprehensively investigate the processes of transformation in the aviation industry by its main functional directions and to identify their characteristic features, focusing on the integration of Ukrainian aviation into the European and world aviation space, air traffic trends, innovations in the development of airports and airlines, problems of aircraft construction of different types of aircraft and unmanned aerial vehicles, training aircraft specialists in modern conditions. Results: The new 21st century was also a new stage in the development of civil aviation in Ukraine, which, thanks to the transformations, was characterized by a positive dynamics of its growth. Basically there was a consistent process of integration of domestic aviation into international aviation organizations, the standards and recommended practices of ICAO were being more actively implemented, and air transportation was growing. Innovations in aviation and industrial infrastructure were applied, attention was focused on the problems of aviation safety and flight safety, scientific and technical developments; measures were taken to solve global problems, such as improving the level of environmental friendliness of aviation transport, the quality of training of aviation specialists and the like. However, the strong potential in all areas of the aviation industry is not suffiently used for a variety of external and internal reasons, and solving existing problems will contribute to the sustainable development of both the aviation industry, the economy of Ukraine and international cooperation. [ABSTRACT FROM AUTHOR]

The dynamics and prospects of development of innovative branches of machine building of Ukrain, which the aircraft industry belongs to is researched. Ukraine is one of the few countries in the world with a full cycle (macro technology) in the creation of aviation technology, and has a leading place in the world market in the transport and regional passenger aircraft sector. By the level of development of aircraft industry, Ukraine belongs to the most developed states. The industry accounts for more than 60 enterprises, accounting for about 25% of the employed in engineering in Ukraine. The basis of the industry consists of five large enterprises, in which two thirds of industry employees are concentrated; therefore the research of the prospects of development of the innovative branch of mechanical engineering using the tools of economic-mathematical modeling based on the theory of Markov chains is relevant. Also, on the basis of the correlation-regression analysis of the extent of the influence of the average monthly nominal wage of workers in the mechanical engineering industry on the number of employed workers in the mechanical engineering industry is investigated. [ABSTRACT FROM AUTHOR]

Supersonic particle deposition (SPD) is an additive manufacturing technology with demonstrated potential for the repair of corrosion damage in metallic aircraft components. Repairs via SPD are applied with the aim of restoring damaged components to at least the equivalent structural properties of their original design. A successful SPD repair must have sufficient cohesive strength to prevent further cracking under fatigue loading, and the quality of the repair must be able to be monitored nondestructively on a periodic basis during ongoing operation of the repaired aircraft. In this study, we demonstrate the capability of two nondestructive inspection (NDI) techniques, thermoelastic stress analysis and angle-beam ultrasonic inspection, to both assess the health of an SPD coating and to detect and characterise representative fatigue crack growth beneath it. The results obtained via NDI are explained with reference to the microstructural features of the SPD coating and the substrate, as analysed via optical microscopy. [ABSTRACT FROM AUTHOR]

In laboratories most fatigue testing is uniaxial as many aeronautical components such as wing spars are uniaxially loaded. However important components, such as aero engine disks, operate under multiaxial loading conditions. Hence multiaxial data is desirable to safely design them. This paper describes biaxial fatigue tests carried out under a range of loading conditions with cruciform specimens made of Waspaloy, a nickel based superalloy widely used in the fabrication of aero engine disks. Finite Element modeling of the specimen was performed to set the test conditions and to predict stress-strain fields and failure location. In order to investigate the effect of strain biaxiality, different biaxiality ratios with the same maximum principal stress were considered. Results demonstrate a variation in total life to failure and failure location, confirming the FE predictions. Then the experimental results obtained were used with three groups of multiaxial criteria. Initially, von Mises and elastic strain energy density yield theories were extended to the multiaxial fatigue context. Secondly, the stress invariant based criterion proposed by Crossland was considered, where the maximum shear stress amplitude was calculated through the Minimum Circumscribed Circle and the Maximum Prismatic Hull methods. Lastly, the critical plane approach was investigated by considering the propositions made by Findley and Matake. In general all the criteria probed here gave good predictions. As for the first group, better correlation was obtained with the energy parameter. For the last two groups, Crosslands formulation performed the best, with close agreement with experimental observations. The critical plane criteria gave conservative predictions for uniaxial stress cases and non-conservative for the other assessed conditions. In addition, both criteria misbehaved outside their calibration region, i.e. outside the tension-torsion region, and were unable to properly describe equi-biaxial conditions. [ABSTRACT FROM AUTHOR]

• Interference fit fasteners under load may separate from the hole that they are inserted into. • Separation causes a non-linear stress effect in the vicinity of the hole. • Accelerating crack growth for high stress cyclic loading. • This effect can be discerned using quantitative fractography. • Ignoring this effect in life predictions may result in unconservative crack growth estimations. Interference fit fasteners are a ubiquitous part of modern airframes, incorporated to increase the fatigue life at critical locations. When inserted into a structure, they have a compound effect of inducing residual stresses and changing the stress concentration. Evidence suggests that this stress state may become non-linear under high tensile loading, as the fastener and hole surface may separate. This paper illustrates the importance of including this separation in fatigue analysis of structures containing interference fit fasteners by showing that separation results in an otherwise unexplained acceleration in crack growth. Test specimens with and without fasteners are subjected to a specifically designed test spectrum, and crack growth rates are measured using quantitative fractography. This investigation reveals a statistically significant acceleration in fatigue crack growth only found in the specimens containing interference fit fasteners. Simulations that model the separation effect predict an acceleration, but classic crack growth equations fall short. Ignoring these separation effects is shown to underpredict the growth of cracks under certain conditions by a factor of two or more. [ABSTRACT FROM AUTHOR]

Results of comparative load transfer measurements and fatigue tests on riveted lap joints from Alclad sheets of a configuration representative of the aircraft fuselage are presented. Two different rivet squeeze force values were accounted for and in either case riveted specimens with the interfaying Teflon foil between the sheets to minimize friction, in addition to standard riveted joints without such a layer, were considered. The goal of the investigation was to recognize implications of friction between the mating sheets for the fatigue behaviour of riveted lap joints in order to derive riveting process dependent coefficients to be included in a fatigue life prediction model for this type of connections. [ABSTRACT FROM AUTHOR]

The phenomenon of secondary bending in riveted lap joints of the configuration representative of connections of the aircraft fuselage sheets in the longitudinal direction is investigated experimentally and analytically. The experiments involved strain gauge measurements of secondary bending stresses carried out in close proximity to the fatigue critical section of the riveted lap joint and fatigue tests performed to study the effect of secondary bending on the riveted joint fatigue life. The strain gauge measurement results allowed validation of a simple analytical model proposed by Schijve to estimate secondary bending moments induced in mechanically fastened joints with eccentricities. Variables considered in the fatigue tests were several joint geometry related parameters known to influence the magnitude of secondary bending in the fatigue critical location. It was shown that the fatigue test data for joints of various geometries, which were considerably scattered if the fatigue lives were presented against the applied stress amplitude, could become consolidated within common scatter bands when the lives were plotted in terms of the combined tensile stress amplitude including the bending stress computed from the model by Schijve. [ABSTRACT FROM AUTHOR]

The paper presents a theoretical study of three approaches to identifying the material stress-strain behaviour under the elastomer constrained bending. The relationships for determining the required tool pressure have been revealed. The results of an experimental study of constrained bending for the operating pressure of an elastic medium have proved to be the most close ones to the analytical studies for the plane stress behaviour of the workpiece material. [ABSTRACT FROM AUTHOR]

Fiber metal laminate (FML) is an extremely strong and light material that is widely applied in the structural components of aircraft for weight reduction and improving mechanical properties. However, the effective integration of excellent structural failure tolerance property and superior stress dissipation capacity into one FML material remains a huge challenge. Herein, inspired by the non-linear helical structure of lobster and the linear helical structure of mantis shrimp, a novel bioinspired FML with Janus helical structure was designed and manufactured through the method of hot press forming. Afterwards, low velocity impact tests were carried out to evaluate the impact resistant property. Remarkably, the peak impact force of the bioinspired Janus FML (BJFML) at the impact energy of 40 J was 8216.36 N, which increased by 10.22% compared with the 7454.52 N of traditional cross-ply FML (CPFML). Moreover, the dent depth of the BJFML (5.95 mm) decreased by 28.23% compared with that of CPFML (8.29 mm). Finally, the finite element simulation was conducted systematically. In fact, the non-linear helical arrangement greatly hindered crack propagation and the periodic linear structure improved its load homogenizing ability for impact forces, thus improving structural failure tolerance, strengthening stress dissipation, and synergistically enhancing the impact resistance. [ABSTRACT FROM AUTHOR]

Development trends in aeronautics involve a better employment of electric motors also in safety critical hazardous applications until now covered by mechanical systems. The electromechanical actuators (EMAs) are gaining a growing interest owing to their force and power density capability and the high dynamical performance by electronic control. Hence, very compact and high-efficiency drives can be designed, with satisfactory characteristics from the reliability point of view. This paper refers to a rotor damper system for helicopter application, using specifically designed permanent-magnet motors as EMAs. Design criteria and details will be presented focused on the integration of the electrical machine inside such specific application. Reports of analyses and tests carried out on the motor prototypes are included to confirm the capabilities and the performances of the proposed solution. [ABSTRACT FROM PUBLISHER]

Abstract: Effects of variables related to design and production of riveted lap joints representative of longitudinal sheet connections for a pressurized transport aircraft fuselage were experimentally investigated. Specimens from an aircraft Al alloy D16Cz Alclad sheets of three different thicknesses (1.9, 1.2 and 0.8mm) were assembled under load control using round head rivets and rivets with the compensator from a P24 Al alloy. For the joints from 1.9mm thick sheets fatigue tests indicated a dependency of the crack initiation site and crack path on the squeeze force level and on the rivet type. At the same time, increasing the squeeze force led to improved fatigue properties of the joints, specimens assembled using the rivets with the compensator showing fatigue lives longer than joints with the round head rivets. All observed trends have been explained based on hole expansion and load transfer measurements. For thin sheets connected using the round head rivets, local deformations under the rivet driven head arising during the rivet installation promoted crack initiation and failure in the adjacent sheet. Fatigue test results indicated that the detrimental effect of this type imperfections could outweigh the benefits associated with a decrease in secondary bending due to thinning the sheets. The rivets with the compensator were observed to cause significant local imperfections beneath the manufactured head, which adversely affected the fatigue performance of the joints from thin sheets. [Copyright &y& Elsevier]

Purpose - The Embedded GPS/INS System (EGI) has been used more widely as central navigation equipment of aircraft. For certain cases needing high attitude accuracy, star sensor can be integrated with EGI to improve attitude performance. Since the filtering-correction loop has already built in finished EGI product, centralized or federated Kalman filter is not applicable for integrating EGI with star sensor; it is a challenge to design multi-sensor information fusion algorithm suitable for this situation. The purpose of this paper is to present a double-layer fusion scheme and algorithms to meet the practical need of constructing integrated multi-sensor navigation system by star sensor assisting finished EGI unit. Design/methodology/approach - The alternate fusion algorithms for asynchronous measurements and the sequential fusion algorithms for synchronous measurements are presented. By combining alternate filtering and sequential filtering algorithms, a kind of double-layer fusion algorithms for multi-sensors is proposed and validated by semi-physical test in this paper. Findings - The double-layer fusion algorithms represent a filtering strategy for multiple non-identical parallel sensors to assist INS, while the independent estimation-correction loop in EGI is still maintained. It has significant benefits in updating original navigation system by integrating new sensors. Practical implications - The approach described in this paper can be used in designing similar multi-sensor information fusion navigation system composed by EGI and various kinds of sensors, so as to improve the navigation performance. Originality/value - Compared with conventional approach, in the situation that centralized and federated Kalman filter are not applicable, the double-layer fusion scheme and algorithms give an external filtering strategy for measurements of finished EGI unit and star sensors. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to investigate the effect of spanwise shape of the leading edge on unsteady aerodynamic characteristics of wings during forward flapping and gliding flight. Design/methodology/approach - A computational fluid dynamics approach was conducted to analyze the flow around airfoils with sinusoidal-like protuberances at a Reynolds number of 10[sup 4]. Three-dimensional time-dependent incompressible Navier-Stokes equations are numerically solved by using finite volume method. A multigrid mesh method, which was applied to the situation of fluid across the heaving models is used to simulate this type of flow. The simulations are performed for the wavelength between neighbouring peaks of 0.25c and 0.5c. For each wavelength, two heights of the tubercles which are 5 per cent and 10 per cent of the chordwise length of wing, are employed on the leading edge of wings. The aerodynamic forces and flow structure around airfoils are presented and compared in detail. Special attention is paid to investigate the effect of leading-edge shape on the fluid dynamic forces. Findings - Present results reveal that the wings with leading-edge tubercles have an aerodynamic advantage during gliding flight and also have the potential advantages during flapping forward flight. Originality/value - On the basis of computational study, an improved scenario for flapping wing microaviation vehicle has been originally proposed. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to present the procedure and results from instrumented flight test performed on the flapping MAVs being developed by the authors. A test is performed using a test measurement system to obtain the real characteristics of the flapping vehicles during their flight. Design/methodology/approach - The test is performed in an indoor flight test facility, equipped with a motion capture system and tracking cameras. Spatial position data are obtained from the vehicles with retro-reflective tracking markers attached. A quantitative analysis is carried out through the investigation and interpretation of the test data for the flight performance assessment of the vehicles. Findings - The finding of the analysis addresses that the test enabled the numerical measurement of vehicles' flying performance and shows the present vehicles have combined characteristics of both birds and insects. Practical implications - The test metrics attempted in the present study are applicable to the test and evaluation of general flapping micro air vehicles. Thus, this testing method will be useful for the development of future micro air vehicle system. Originality/value - Full-scale instrumented flight test and measurement of performance parameters of flapping micro air vehicles other than visual observation are unprecedented and expected to present the guideline of systematic test and evaluation of flapping micro air vehicles. [ABSTRACT FROM AUTHOR]

Purpose - This is the second of two companion papers presenting the results of research into a contra-rotating propeller designed to drive a super manoeuvrable micro air vehicle (MAV) and is devoted to the experimental results. The first paper presented the design process and numerical analyses. Design/methodology/approach - Most of experiments were conducted in the wind tunnel. Both contra-rotating and conventional propellers were tested. The test procedures and equipment are described first. The attention is focused on the design of an aerodynamic balance used in the experiment. Then, the measurement error is discussed, followed by presentation of the wind tunnel results. Finally, an initial flight test of the MAV equipped with contra-rotating propeller is briefly described. Findings - Wind tunnel experiment results fall between theoretical results presented in the first part of the paper. The application of contra-rotating propeller allowed to develop the propulsion system with zero torque. Moreover, the efficiency achieved appeared to be a few percent greater than that for a standard conventional propulsion system. The concept was finally proved during the first test flight of the new MAV. Research limitations/implications - The propeller was designed for a fixed wing aeroplane, not for helicopter rotor. Therefore, only conditions characteristic for fixed wing aeroplane flight are tested. Practical implications - The designed contra-rotating propeller can be used in fixed wing aeroplane if torque equal to zero is required. Originality/value - Original design of the balance is described for the first time, as well as test procedures applied in this experiment. Most of wind tunnel test results are also new and never published before. [ABSTRACT FROM AUTHOR]

Purpose - This is the first of two companion papers presenting the results of research into a contra-rotating propeller designed to drive a super manoeuvrable micro air vehicle (MAV). The purpose of this first paper is to describe the design process and numerical analyses. The second paper is devoted to the experimental results verifying the computations. Design/methodology/approach - Software based on the analytical formulas derived by Theodore Theodorsen was used in the design procedure. Three-dimensional finite-volume simulation, performed with the use of commercial software verified the results. Finally, two-dimensional simulation was conducted to explore the effect of the propeller-wing interaction. The meshes applied in these analyses are described. Findings - Propeller geometry received as a result of the design procedure is presented. The computation results for different turbulence models applied are discussed. Time dependent characteristics of contra-rotating propeller are presented as well as conclusions regarding propeller-wing interaction. Research limitations/implications - Propeller was designed for a fixed wing aeroplane, not for helicopter rotor. Therefore, conditions characteristic for fixed wing aeroplane flight are analysed only. Reynolds numbers below 50000 are considered. Practical implications - Designed contra-rotating propeller can be used in fixed wing aeroplane if torque equal to zero is required. Software based on the formulas derived by T. Theodorsen can be used to design the propellers. Originality/value - Software applied in the design procedure was originally developed by one of authors although it is based on the formulas derived by T. Theodorsen. Contra-rotating propeller simulation results for different turbulence models are discussed for the first time. Moreover, unique time dependent characteristics of contra-rotating propeller are presented. [ABSTRACT FROM AUTHOR]

Abstract: Results of an experimental research on the influence of several production related factors on the fatigue behaviour of simple riveted lap joint specimens under constant amplitude loading conditions are presented. The specimen geometry is representative for the longitudinal joints of the aircraft fuselage. The variables considered are the rivet type and material, the sheet material and the squeeze force. Some comparisons are made between results for Russian and Western aluminium alloys used in the aircraft industry for sheets and rivets. The measurements of the driven head dimensions for a range of squeeze force levels and fatigue test results for rivets installed with various squeeze forces indicate that the squeeze stress rather than the rivet driven head dimensions is a safe standard for the quality of the rivet installation. The superior fatigue performance of a rivet with the so-called compensator compared to the round head and universal rivet is noted. The underlying reason is the better hole filling achieved due to the presence of the compensator. Observations on crack growth indicate that crack initiation covers the major part of the joint fatigue life. [Copyright &y& Elsevier]

Abstract: This paper presents an example of the fractographic analysis of a typical riveted joint after fatigue testing. The loading used in the tests was derived from a load spectrum representing the real operational conditions of the PZL I-22 Iryda aircraft. The fatigue crack-growth rates derived from macroscopic and microscopic analyses of the fatigue fracture surfaces have been compared. It seems that for practical purposes, like the fracture analysis of parts or components, results of the macroscopic method are closer to the observed crack-growth rates. The presented results refer to the propagation of cracks in the wing skin under stable crack-growth conditions. [Copyright &y& Elsevier]

Abstract: A methodology for the computational modeling of the fatigue crack growth in pressurized shell structures, based on the finite element method and concepts of Linear Elastic Fracture Mechanics, is presented. This methodology is based on that developed by Potyondy [Potyondy D, Wawrzynek PA, Ingraffea, AR. Discrete crack growth analysis methodology for through crack in pressurized fuselage structures. Int J Numer Methods Eng 1995;38:1633–1644], which consists of using four stress intensity factors, computed from the modified crack integral method, to predict the fatigue propagation life as well as the crack trajectory, which is computed as part of the numerical simulation. Some issues not presented in the study of Potyondy are investigated herein such as the influence of the crack increment size and the number of nodes per element (4 or 9 nodes) on the simulation results by means of a fatigue crack propagation simulation of a Boeing 737 airplane fuselage. The results of this simulation are compared with experimental results and those obtained by Potyondy . [Copyright &y& Elsevier]

Iterative life cycle models have become popular in software engineering, e.g. in agile development. In contrast, the waterfall model appears to prevail in manufacturing engineering disciplines. This includes aircraft engineering and Boeing's project for developing its most recent passenger aircraft, the 777. The paper walks through the phases of the 777's development and compares this process to iterative development. The comparison suggests two observations: Firstly, the over-all waterfall approach in the 777 project appears to be well-motivated by the physical, manufactured nature of aircraft components such as wings, in addition to safety concerns. Secondly, several iterative elements in the development of the 777 can also be identified. A major source of these is digitalization of development, in particular the use of CAD tools for a process called digital preassembly. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to evaluate the statistical fatigue properties of a thin sheet of a stainless steel for use as an abrasion strip on helicopter rotor blades made of glass fiber/epoxy composite materials. The sheet was an AISI 301 1/4-hard stainless steel. Tensile fatigue tests were conducted up to 107 cycles on unnotched specimens under constant amplitude loading in the large-strain regions for stress ratios (=minimum stress/maximum stress) R=0 and 0.3. The test results provided S–N relationships for R=0 and 0.3, the standard deviation of fatigue life and fatigue strength in the inclined part and the mean and standard deviation of fatigue strength in the horizontal part of the S–N curve for R=0. Strain measurements during fatigue tests clarified the change of true stress in specimens and estimated the fatigue crack propagation period. SEM revealed the details of the fatigue-fracture surfaces formed by the repetition of large strains. The applicability of this material as an abrasion strip is discussed on the basis of the test results. [Copyright &y& Elsevier]

The paper presents research on the interlayer adhesion of fibre metal laminate composites in a 3/2 configuration made of 0.4 mm thick 2024-T3 ALCLAD aluminium sheets. A polymer-fibrous layer is used to make a prepreg based on glass fibres with a thermosetting epoxy matrix. Experimental research presented in this paper was aimed at determining the impact of thermal shocks on the mechanism of composite destruction in the three-point-bending test. The samples were subjected to 100 °C temperature gradient thermal shocks in the form of cyclic temperature changes in the range of −40 °C and +60 °C. The number of cycles was 500 and 1000, according to the specific variant. The damage characteristics were observed by Scanning Electron Microscopy to assess failure modes. Samples subjected to thermal shocks are characterised by lower stiffness in relation to samples not exposed to repeated thermal shocks. It was found that both the failure mode and interlaminar shear strength depend on the number of thermal shock cycles. Under the influence of cyclic temperature changes in the test samples, metallic layers undergo cyclic expansion and shrinkage while the layer of fibre-reinforced composite with relatively low thermal expansion does not undergo large deformations. [ABSTRACT FROM AUTHOR]