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The impact behavior of a carbon-Kevlar hybrid composite, widely used in sport car manufacturing, was evaluated. To highlight the hybridization effect, comparative analyses were performed with the basic CFRP laminate having the same lay-up. Tensile, bending and low velocity impact tests, followed by nondestructive inspections, highlighted that Kevlar first lamina hybridization leads to an increment in specific impact strength, up to 55%. To assess the most reliable technique to detect the impact damage, nondestructive evaluation was performed by pulsed thermography, phased array ultrasonic technique, computed tomography and digital radiography. Phased array ultrasonic technique can be considered the most appropriate technique.

The complexity of the damage behavior of composite materials due to the simultaneous evolution of different mechanisms involving matrixes, reinforcements and interfaces is a topic which, despite decades of knowledge, still requires specific insights and is the subject of a multitude of researches. Recently, with the attention increasingly directed towards biobased raw materials, these aspects have shown a renewed interest, prompting the need for further contributions. In this context, this experimental research work aims to investigate the damage behavior of laminate structures based on a commercial polyamide obtained from castor oil, reinforced with woven basalt fibers. The focus was on samples obtained by hot compaction using two different pressure profiles and subjected to low velocity impacts with different impact energies. Damage analysis was performed on impacted specimens using ultrasonic phased array inspections and pulsed thermography. The non-destructive analysis supported low velocity impact test results, confirming the different contribution of the damage mechanisms involved, as expected from the different level of compaction of the materials, in turn due to diverse manufacturing conditions. This research has emphasized the complementarity and effectiveness of these two non-destructive characterization techniques, providing potentially useable results for the optimal design and manufacturing of biocomposite systems.

Integration of lightweight and sustainable solutions in marine structures design is essential to achieve weight reduction goals and improve structural response. A key step to assess the reliability of innovative structural solutions is represented by large-scale experimental investigation. The current paper deals with the analysis of a lightweight ship balcony overhang, which includes an aluminium honeycomb sandwich structure and bimetallic welded joints. The design of the ship balcony overhang was previously performed, as an illustrative example, with the aim of suggesting the replacement of common marine structures with more green and lightweight alternatives. In order to validate the design procedure and to assess the feasibility of the suggested solution, an experimental investigation on a large-scale structure was performed. The ship balcony overhang was tested under bending with a configuration representative of severe loading conditions for ships balconies. The experimental analysis allowed the evaluation of the structure’s strength, stiffness and failure modes, which are useful data to improve the design methodology of such structures and to calibrate numerical models. Comparison with similar structures reported in literature were performed in order to assess the benefits and drawbacks of the suggested lightweight structure.

The lumbar intervertebral devices are widely used in the surgical treatment of lumbar diseases. The subsidence represents a serious clinical issue during the healing process, mainly when the interfaces between the implant and the vertebral bodies are not well designed. The aim of this study is the evaluation of subsidence risk for two different devices. The devices have the same shape, but one of them includes a filling micro lattice structure. The effect of the micro lattice structure on the subsidence behavior of the implant was evaluated by means of both experimental tests and finite element analyses. Compressive tests were carried out by using blocks made of grade 15 polyurethane, which simulate the vertebral bone. Non-linear, quasi-static finite element analyses were performed to simulate experimental and physiologic conditions. The experimental tests and the FE analyses showed that the subsidence risk is higher for the device without micro lattice structure, due to the smaller contact surface. Moreover, an overload in the central zone of the contact surface was detected in the same device and it could cause the implant failure. Thus, the micro lattice structure allows a homogenous pressure distribution at the implant-bone interface.

The progress in additive manufacturing has remarkably increased the application of lattice materials in the biomedical field for the fabrication of scaffolds used as bone substitutes. Ti6Al4V alloy is widely adopted for bone implant application as it combines both biological and mechanical properties. Recent breakthroughs in biomaterials and tissue engineering have allowed the regeneration of massive bone defects, which require external intervention to be bridged. However, the repair of such critical bone defects remains a challenge. The present review collected the most significant findings in the literature of the last ten years on Ti6Al4V porous scaffolds to provide a comprehensive summary of the mechanical and morphological requirements for the osteointegration process. Particular attention was given on the effects of pore size, surface roughness and the elastic modulus on bone scaffold performances. The application of the Gibson–Ashby model allowed for a comparison of the mechanical performance of the lattice materials with that of human bone. This allows for an evaluation of the suitability of different lattice materials for biomedical applications.

Experimental tests were carried out to assess the fatigue strength of four types of welded joints, made of AH36 steel and used for ship structures. The joints differ for the presence of weld defects and for the thickness value. Fatigue tests were carried out applying axial cyclic loads at a frequency of 20 Hz and at a stress ratio R = 0.5. The temperature e increment of the specimen surface was detected during the load application by means of an infrared camera. The analysis of the thermographic images allowed the assessment of both the fatigue strength of the welded joints, applying the rapid thermographic method, and the S-N curve by the energy approach. Moreover, 3D computed tomography was used for the analysis of the defective welded joints.

In the railway field, the safety of passengers and the service life of train components are a crucial issue. For this reason, continuous periodic inspections by non-destructive techniques are required. Among these, ultrasonic tests are widely used in this field, even though the conventional ultrasound techniques have the disadvantage of requiring the disassembly of the wheels and of putting the train out of service. This procedure is expensive and time-consuming and can be neglected if non-contact ultrasonic techniques are used. In this work, the authors present an experimental research on some defects, artificially obtained on a railway wheel supplied by Trenitalia Spa, by adopting three different experimental setups and comparing the results. The proposed method uses laser equipment in generation and reception of the ultrasonic waves. The receiving unit combines a continuous wave laser and an interferometer in order to detect the surface displacements. In addition, when used in service conditions, the receiving by the interferometer is facilitated, because the tread of the wheel is very reflective (thanks to wheel – rail contact). The research aims at optimizing the experimental setup through a number of measurements carried out by varying some experimental parameters to evaluate the robustness and reliability of the technique.

One of the most important design strategies for increasing the speed and/or efficiency of marine vehicles is that of weight reduction. This can be achieved by optimising structural design via judicious distribution of the most apt materials and via the application of innovative lightweight structures. Sandwich structures are ideal candidates for structural lightening since they provide excellent mechanical properties at low densities, and a wide range of properties via intelligent selection of face-sheet and core materials, and configurations. Further, sandwich structures selection for marine vehicles needs to consider manufacturing feasibility for large structures, sustainability issues and materials compatibility with the aggressive marine environment. As a possible alternative to the ubiquitous glass reinforced plastic (GRP) fibre composite sandwich materials used for marine vehicles, all-aluminium sandwich structures have several attractive properties such as light weight, high mechanical properties, sustainability, and corrosion resistance. Common architectures for metallic cores include: honeycomb, foam, corrugated and lattice. This work aims to evaluate the effectiveness of aluminium honeycomb sandwich structures in marine applications by providing a comparison with other lightweight solutions. Bending stiffness was used as the criterion to select honeycomb sandwich panels allowing valid comparisons with typical marine GFRP sandwich panels. A case study based on a possible replacement of a GFRP ship balcony with an equivalent aluminium honeycomb sandwich structure was introduced. The proposed balcony was analysed with a simplified numerical model, which gives useful information for the design of the proposed structure and the experimental set up of full scale tests. The acquired information can be applied to support the design of lightweight honeycomb sandwich panels to be used for balconies, decks, floors, ceilings and other structural elements of marine vehicles.

Ballast impacts can initiate surface defects that cause abrupt failure of the axle and derailment of the railway vehicle. According to the Federal Railroad Administration the axle and bearing failure costs around 89 million dollars and causes 46 derailments in the US per year (2005–2010). In this study, the authors have suggested a novel protective mechanism (Metallic Foam Shell – MFS) by using a lightweight sandwich panel. At the first step, a preliminary study is conducted, followed up by the numerical simulations to determine the applicable materials. At the next step, experimental tests were performed to assess the efficiency of the suggested device against flying ballast impacts. An extended non-destructive (NDT) evaluation has been performed in order to find the most suitable technique for damage detection of the proposed device when on-service. The studied cases were GFRP and Aluminium sandwich panels, having an aluminium foam core with different densities and thicknesses. The results showed that the MFS can absorb up to 90% of the initial impact energy and significantly decrease the chance of rebounding impact to the other components. Moreover, the results were also analysed in order to propose the most reliable NDT method for this specific application.

The widespread additive manufacturing technology for producing components having complex geometries has increased the attention towards new reinforced materials, whose internal structure can be designed ad hoc on the required mechanical performance. Moreover, fused deposition modelling (FDM) technology allows the building of continuous fibre-reinforced thermoplastic composites. Due to this innovative technology, there is a lack of knowledge mainly about the impact behaviour of these materials, also considering that the main demand comes from the transportation field (automotive, aircraft, etc.), where the impact event is always possible. Thus, the aim of this research is the investigation of the impact behaviour of specimens obtained by continuous fiber fabrication technique, where Onyx and nylon white filaments were used as matrices and glass fibres for reinforcement. Onyx is a nylon mixed with short carbon fibres. An extensive non-destructive evaluation was performed on the specimens subjected to impact tests to assess the impact damage tolerance of these materials and to measure the damage extension as well. Nevertheless, considering that different non-destructive techniques were employed, the research aims also to suggest the most suitable and reliable technique to detect damage, mainly by on-site inspection.

One of the main focuses in transportation engineering is the application of sandwich materials in order to create safer and efficient vehicles. The main focus of this study was the application of 3D computed tomography for analyzing the responses of sandwich panels with micro lattice core subjected to impact loading. Micro lattice specimens were manufactured using Ti-6Al-4V powder by means of a direct metal laser sintering system. A theoretical model was applied for predicting the failure initiation loads under impact loading. The predictions presented good consistency with the experimental measurements. The 3D computed tomography system was used for the analysis of the collapse modes of the micro lattice sandwich panels after low-velocity impact tests. Experimental and theoretical results proved that lightweight sandwich panels with micro lattice cores are excellent energy absorbers and, therefore, they could have significant applications in the transportation industry. © 2018, © IMechE 2018.

Titanium alloys are increasingly used for structural applications in transportation engineering (aerospace, automotive, railway, marine industry) because of their interesting properties (high mechanical properties to weight ratios, excellent corrosion resistance). In the present research work, the very high cycle fatigue behaviour of Ti–6Al–4V alloy of both bimodal and basketweave microstructures were investigated and compared. Fatigue tests at a very high number of cycles with R = −1 were carried out on titanium alloy - grade 5 specimens, cut from a forged flange used on a commercial aircraft. The experimental tests showed that this alloy has an always decreasing S-N curve, even for a number of cycles greater than 10 9 . It is the typical behavior of some alloys used in the aircraft industry, such as aluminum, titanium, nickel and high-strength steels. Moreover the very high cycle fatigue tests demonstrated that the Ti–6Al–4V alloy with bimodal microstructure has fatigue strength higher than the Ti–6Al–4V alloy with basketweave microstructure. The effect of microstructure on fatigue mechanism focused on internal crack initiation has been discussed through SEM observation of sub-cracks underneath the fracture surface. The temperature evolution during the tests was detected by means of IR cameras to study the temperature effect on the material response.

The aim of this study was the analysis of the mechanical behaviour of a partially porous lumbar custom-made cage by means of a subject-specific finite element analysis (FEA). The cage, made of Ti6Al4V ELI alloy, was produced via electron beam melting (EBM) process and surgically implanted in a female subject, 50 years old. The novelty of this study was the customized design of the cage and of its internal structure, which is impossible to obtain with the traditional production techniques. The 3D model of the spine was obtained from the computed tomography (CT) of the patient. Moreover, high-resolution industrial CT was also used to reconstruct a 3D model of the cage, with its real (as-produced) features, such as superficial roughness, morphology of the bulk and of the porous structure. The workflow was divided in several steps: the main finite element analyses were non-linear and quasi-static regarding: the rhombic dodecahedron (RD) unit cell of the porous structure; the device; the whole L4-L5 motion segment with the implanted cage. Stress distribution was calculated under compression load for all models. For the RD unit cell, the maximum stress appeared at the connected cross nodes, where notch effect was present. For the cage subjected to a load of 1 kN, the porous structure did not present any functional failure. For the whole biomechanical system subjected to a physiological load of 360 N, the calculated stress in the bone was smaller than its yield strength value. On the axial view, a zone with higher compressive stresses was present on the L5 vertebral body. This was due to the contact stress between the cage and the vertebra. From the comparison between FE results and the CT images of the spine, bone remodelling was supposed, with the formation of new bone. Graphical abstract Workflow showing the phases of the research.

The present study deals with the wear behaviour and failure analysis of cylinder blocks belonging to an axial pistons pump. An anti-friction coating made of high-lead bronze was joined on the blocks by a casting process. The production parameters, in terms of cooling rate and casting temperature, were changed to optimize the performance of the coating by obtaining different microstructures. The blocks were subjected to full-scale wear tests by simulating the worst operative conditions in a test-bench. During the tests, the coating of some cylinder blocks failed after few hours. In order to obtain a correlation among such behaviour, wear performance and microstructure, failure analysis was carried out by means of optical and scanning electron microscopy with energy dispersive spectrometry (SEM/EDS). Confocal topography has been carried out to analyse wear tracks after the tests and to evaluate wear mechanism. The experimental tests showed that the failure of the coating was mainly due to the inhomogeneity in the distribution of lead segregations depending to the cooling rate of the casting process.

Additive manufactured titanium alloy microlattice structures are attracting the attention of numerous industrial fields, since they allow a customised and optimised design of components and structures. In the current work, Electron Beam Melting (EBM) technique was used to produce Ti6Al4V ELI rhombic dodecahedron (RD) microlattice structures. Preliminary tests on bulk specimens highlighted the effect of surface roughness on mechanical response. A confocal microscope was used to characterise surface topography and to obtain a precise evaluation of surface roughness, which is a critical point in EBM technique. Three different unit cell sizes were selected in order to investigate the effect of cell dimensions on microlattice mechanical properties. Morphological evaluations were performed through Computed Tomography (CT) technique, which allowed the comparison of the real models to the designed one. Discrepancies between actual and CAD geometries were observed, with increasing importance for lower cell sizes. Quasi-static compression tests and low velocity impact tests were performed on RD lattices, highlighting a decrease in mechanical properties with the increase of cell size, except for the specific energy absorption, which depends also on lattice density. A heat treatment was performed on lattice structures, but its effect on mechanical properties was negligible, mainly for the higher cell size lattice, proving the lack of significant residual stresses in lattices produced via EBM. Thermographic observations during compression tests allowed a clear identification of the failure instant and the deformation mode, which occurs along a 45° inclined plane.

The aim of this scientific work is the analysis of rhombic dodecahedron micro-lattice structures under quasi-static and dynamic loading. The effect of unit cell size and strut diameter on mechanical properties was also considered. The specimens were designed by means of Materialise Magics® software and produced using Ti6Al4V ELI metal powder by Arcam Q10 electron beam melting (EBM) 3D printer, with the scientific collaboration of Mt Ortho Srl. The microstructure effect on the mechanical properties was analysed by optical and electron microscopy and Computed Tomography was used to analyse the morphology of unit cells. The experimental results show that these porous structures are very suitable for building custom-made implants in the field of orthopaedics and reconstructive neurosurgery. Moreover, by means of EBM additive manufacturing complex geometries, which are difficult to produce by conventional technologies, can be designed and produced.

Passengers’ safety and in-service life of wheelset axles play an important role in railway vehicles. For this reason, periodic inspections are necessary. Among non-destructive techniques, ultrasonic ones are widely applied in this field. The main disadvantage of conventional ultrasonic techniques is that the overall inspection of wheels requires the train to be put out-of-service and disassembly each part, which is time-consuming and expensive. In this paper, a non-conventional non-contact laser ultrasonic inspection for train wheels is proposed. The proposed method uses a laser interferometer to receive the ultrasonic wave without contact. The receiving system allows choosing the distance between the surface to be inspected and the interferometer, overcoming any encumbrance issue. The experimental investigation is carried out on standard-reproduced defects in order to evaluate the reliability and the accuracy of the technique and to verify its applicability for railway components, as wheels, which have a complex geometry. The experimental setup consists of a pulsed laser for the ultrasonic wave generation. The receiving unit combines a continuous-wave laser and an interferometer in order to acquire the surface out-of-plane displacements. Surface and internal standard defects are detected by collecting all the A-scans in a B-scan map. The results are promising for the application of the laser technique to detect both surface and internal defects on in-service components.

Aluminium foam sandwich structures have excellent energy absorption capacity, combined with good mechanical properties and low density. Some of the authors of this paper proposed an innovative Metallic Foam Shell protective device against flying ballast impact damage in railway axles. A closed-cell aluminium foam was chosen for the Metallic Foam Shell device. The main goal of this study was the experimental investigation of the impact responses of aluminium foam panels. Low velocity impact tests were carried out at different energies on different types of aluminium foam panels in order to investigate the effects of some parameters, such as core thickness, skin material and layer. Tests were conducted at repeated impacts on aluminium foam panels without and with skins made of aluminium and glass fibre-reinforced polymer. The experimental results were compared and the impacted panels were investigated by means of the nondestructive techniques ultrasonic phased array and digital radiography.

Due to its good mechanical characteristics, low cost and high availability in the current market, sisal fiber is one of the most used for the manufacturing of biocomposites in various industrial fields (automotive, marine, civil construction etc.). The particular sub-fibrillar structure of the sisal fiber (similar to aramid fibers) and the corresponding anisotropic behavior detected by recent research activities, suggest that such biocomposites should exhibit also high impact strength, in such a way to permit their advantageously use also for the manufacturing of crashworthy components (bumpers, helmets, protection systems etc.), that are at the same time also eco-friendly, lightweight and cheap. Through a low-velocity impact tests campaign, integrated by computer tomography (CT) and carried out on various “green epoxy”/sisal laminates, by varying the main influence parameters such as reinforcement distribution, fiber volume fraction and lay-up, it has been detected that angle-ply laminates exhibits specific impact performances superior to those of biocomposites reinforced by other natural fibers (flax, hemp, jute, etc.), and comparable with those of the best composites specially reported in literature, so that they can be actually used to substitute the synthetic materials for the manufacture of interesting eco-friendly energy absorbing devices, that are also lighter and cheaper.

This scientific paper focuses on the application of an advanced non-destructive technique for an effective inspection of railway axles. The method pertains to ultrasonic techniques, which are widely used in the railway field. The experimental investigation was carried out on simulated defects tooled near the cross section reduction of the axle, in order to simulate fatigue cracks which, due to notch effect, can trigger crack propagation and axle failure. The aim of this research activity is to evaluate how efficiently the proposed technique detects defects and to verify its applicability to axles with a black coating for protection. In view of the experimental setup, comprising a pulsed laser for ultrasonic waves generation and a continuous beam laser plus an interferometer as the receiving unit to measure surface displacements, the presence of a black coating represents a major challenge in terms of signal detection. Nonetheless, defects were detected by collecting all the waves in a B-scan map and data were processed by cross-reading A-scans and B-Scans in correspondence of each defect analysed. Results of the analysis show how very promising and robust the application of the proposed laser ultrasonics technique is in defect detection on painted railway axles.

The aim of this research is the investigation of foam-filled honeycomb sandwich panels under in-plane impact loading and the analysis of their crashworthiness. This paper presents a finite element analysis of foam-filled honeycomb sandwiches under in-plane impact loading. Three different aluminium honeycombs filled with three different polyurethane foams were considered in the numerical simulation, and results were compared with those obtained for bare honeycomb panels. For what concerns the crashworthiness analysis, the response of the foam-filled honeycomb panels under out-of-plane impacts was compared with those of unfilled honeycomb panels and circular tubes.

Currently, the technological progress in the engineering fields requires that the design lifetime of many components exceeds 107 loading cycles. The ultrasonic testing machines allow loading the specimen with 20 kHz frequency, allowing reaching gigacycles within a relatively short time, but the high value of frequency produce a high heating of the specimen. A controversy is still opened in literature about the effect of the temperature increase on the fatigue response. This aspect was investigated in the present study. Very high cycle fatigue tests were carried out on AISI4140 steel at frequency f = 20 kHz and stress ratio R = −1 with and without cooling the specimen during the test. The temperature evolution was detected during the whole fatigue test by means of an infrared camera. The fracture mechanism of the investigated steels was evaluated by means of several experimental techniques (Thermography and Optical Microscopy).

Aluminium honeycomb sandwich panels are an interesting lightweight structural solution for several applications such as marine structures, aerospace, automotive and aeronautics. In many of these applications, in-service conditions produce fatigue loadings: as a result, safer use of aluminium honeycomb sandwich structures requires a deep knowledge of their fatigue response, which was seldom studied in previous literature. The aim of the current study is to evaluate the fatigue response of aluminium honeycomb sandwich panels subjected to three-point bending loading conditions. The experimental investigation was performed on a commercial aluminium honeycomb sandwich structure with an overall thickness of 11 mm. A preliminary static analysis was performed both under three and four point bending conditions. The static tests allowed the identification of the static bending strength and the absence of a significant strain rate influence. Crashworthiness parameters were evaluated and a slight better performance was found under four point bending. The combination of static tests with Computed Tomography analysis resulted in the observation of the phenomena involved in static bending response of aluminium honeycomb sandwich structures, which are mainly dependent on cell walls buckling. Fatigue tests were conducted under three-point bending conditions. The influence of boundary conditions on fatigue life and on collapse modes were investigated by considering different supports spans. For one condition the S-N curve was obtained and its equation was compared to literature results. Two different collapse mechanisms were observed depending on the supports span: for larger supports span a fracture of the tensioned skin was observed, whereas lower supports span produced core shear. The former mode differed significantly from static failure with the same boundary conditions. In both cases, failure occurred suddenly and this should be taken into consideration in industrial applications. An analytical model was applied to predict fatigue collapse modes and limit loads. A fatigue failure map describing the relationship between supports span, collapse modes and fatigue limit loads was obtained, in order to provide a quantitative tool for aluminium honeycomb sandwich structures design. The fatigue failure map was able to accurately predict the experimental results.

Honeycomb sandwich structures are increasingly used in the automotive, aerospace and shipbuilding industries where fuel savings, increase in load carrying capacity, vehicle safety and decrease in gas emissions are very important aspects. The aim of this study was to develop the theoretical methods, initially proposed by the authors and by other researchers for the prediction of low-velocity impact responses of sandwich structures. The developed methods were applied to sandwich structures with aluminium honeycomb cores and glass-epoxy facings for the assessment of impact parameters and for the prediction of limit loads. The values of model parameters were compared with data reported in literature and the predictions of the limit loads were validated by means of the experimental data. Good achievement was obtained between the results of the theoretical models and the experimental data. The failure mode and the internal damage of the sandwich panels have been investigated using 3D computed tomography, which allowed the evaluation of parameters of energy balance model, and infrared thermography, which allowed the detection of the temperature evolution of the specimens during the tests. The experimental and theoretical results demonstrated that the use of glass-epoxy reinforcement on aluminium honeycomb sandwiches enhances the energy absorption and load carrying capacities. © 2016, © The Author(s) 2016.

As a common type of energy absorbers, thin-walled structures have been extensively used in crashworthiness application in many industries. The goal of this research is the optimisation of the crushing parameters of corrugated tubes in terms of the number and shape of corrugations. Six different configurations were experimentally investigated; one refers to the straight tube without configurations and the others to corrugated tubes with different geometrical parameters. First, lateral compression tests were carried out and the experimental results were used to validate the finite element models. Other six different configurations of corrugated tubes were analysed by means of finite element simulations. The obtained results demonstrate the advantage of the corrugated tubes with respect to the straight tube in terms of the total absorbed energy and the crushing load. Moreover, the geometrical shape of corrugation (i.e. the ratio of corrugation base to its depth) plays an important role in enhancing the efficiency of the corrugated tubes. ? 2017, ? 2017 Informa UK Limited, trading as Taylor & Francis Group. Qatar National Research Fund (a member of Qatar Foundation) [grant number GSRA2-1-0611-14034]. Scopus

The design and the assembly of the vehicles subjected to the risk of crushing from falling objects have to consider such danger and provide the operators with suitable safety systems. Generally, falling object protective structures for earth moving machines consist of vertical elements, connected by transversal elements, covered by a roof. The latter has the aim to protect the operators from falling objects and it is usually made of a steel skeleton with a metal plate. In this study, sandwich panels were proposed as technical solution for the impact protection from falling objects in earth moving machines. A very light and cheap aluminum honeycomb core (AA3003 alloy and cell size = 19 mm) was considered as design solution and was subjected to static and dynamic full-scale tests. The results were analysed according to the performance requirements of ISO 3449 standard. The experimental results confirmed that the honeycomb structures are well suitable for designing absorber devices in vehicles protective structures in order to ensure occupant safety.

This paper reports the experimental tests, which have been carried out to assess the mechanical properties of Iroko wood laminates used for the construction of a large wooden sailing ship. Three-point bending tests have been carried out on different types of specimens: laminates with 3 layers @ 0° and without scarf joints, laminates with 3 layers @ 0° having the outer layers with scarf joints, and laminates with 4 layers @ 0°/±45°/0° and no scarf joints. The tests have been performed in compliance with the current EN Standards. The analyses of the experimental data allowed the assessment of the mechanical properties of the laminated Iroko wood as well as the influence of scarf joints. The experimental results demonstrated that the presence of scarf joints only affect the strength of the glued laminate, while the stiffness properties in terms of Young modulus in bending and shear modulus, obtained applying the “method of variable support span”, remain essentially the same. The investigated laminates have been also analysed using a 3D computed tomography and an ultrasonic phased array equipment in order to assess the dimensions of possible defects or voids in the adhesive and the dynamic modulus of elasticity. The tomographic measurements of the glue thickness explained the reason of the reduced strength of the scarf joints, due to the inhomogeneity of the glue bond-line. The value of the dynamic modulus of elasticity, obtained by the ultrasonic technique, is slightly higher than the value of the modulus of elasticity obtained by the bending tests. Finally, the experimental findings have been compared with those drawn from both Classical Lamination Theory and Dietz approach, obtaining a good agreement and confirming that the Dietz approach is a fast and easy way to assess the elastic properties of a laminated structure.

The traditional methods of fatigue assessment of metallic and composite materials are extremely time consuming. The thermographic measurements during static tests can be used to predict the fatigue limit. This procedure has been already applied to composite materials. The aim of this study is the application of this procedure for the fatigue assessment of steel welded joints. Static tensile and fatigue tests were carried out on butt welded specimens, made of S355 steel. Two full-field techniques were applied during the tests: digital image correlation and infrared thermography techniques. Fatigue tests at increasing loads were performed by a stepwise succession in order to apply the Thermographic Method. The value of the fatigue limit, obtained by the traditional procedure, was compared with the values predicted by means of the Thermographic Method during stepwise succession fatigue tests and by means of the infrared thermography technique during static tensile tests. The predicted values are in good agreement with the experimental values of fatigue life.

The aim of this scientific work was the analysis of the micro lattice structures under uniaxial quasi-static compression loading with regard to the effect of unit cell size and strut diameter. A wide range of cubic lattice blocks designed in a CAD software were fabricated using Ti6Al4V (Ti64) metal powder and two different production parameters in the direct metal laser sintering machine. The failure modes of the specimens were investigated and the 3D Computed Tomography system was used for the morphological analysis of the struts. An analytical model, developed by Gibson and Ashby, was adapted to the titanium body centered cubic lattices in order to predict their mechanical properties for compressive loading. Moreover, the compressive responses of the lattice structures were also studied using a numerical approach based on finite element analysis. Both experimental and theoretical results presented good agreement in terms of mechanical properties of the body centered cubic lattices and showed that such structures are great energy absorbers. Theoretical approaches gave significant results on the predictions of mechanical properties of these cellular structures, which are suitable for biomedical and transport engineering applications, in order to save manufacturing cost and time. Keywords: Micro lattice structures, Direct metal laser sintering, Lightweight structures, Computed Tomography, Finite element analysis

The paper deals with investigations about mechanical properties of Iroko, a hardwood species used for structures in shipbuilding as glued laminated timber. Experimental tests have been carried out to assess strength, stiffness and density of Iroko in accordance with current EN Standards. All the results obtained by tensile and three-point bending tests, along with the statistical analyses performed to define the characteristics values of some mechanical properties, are reported in the paper. These values allowed to assign the strength class, reported in EN 338 Standard, to the investigated Iroko wood population. The experiments have taken into account both solid timber strips and scarf-jointed strips, in order to evaluate the influence of such a type of joint, which is widely used in wooden shipbuilding on strength and stiffness. Eventually, peculiar investigations have been carried out to analyse the failure mode of some test pieces through special experimental techniques: three-dimensional computed tomography and infrared thermography.

The honeycomb sandwiches are widely used in the transportation engineering for the realization of lightweight and crashworthy structures. However their application requires a better understanding of their impact response. Aims of this paper are the numerical investigation of aluminium honeycomb sandwiches subjected to low-velocity impact tests and the validation of finite element (FE) results. Before and after the low-velocity impact tests at different velocities, three dimensional (3D) reconstructions of the honeycomb panels have been carried out by a computed tomographic system in order to acquire exactly the dimension and the shape of the damage and to obtain information about geometry and cells defects. The FE models have been computed from CT data of the undamaged panels. The direct comparison has been done by superimposing the deformed images obtained from FE analyses and from 3D CT space reconstructions. The numerical model was also validated comparing the FE results with experimental data.