Interlaminar shear strength study on CFRP/Al hybrid laminates with different properties

FML (Fibre Metal Laminate) is a hybrid material that presents outstanding structural properties, such as resistance to cyclic and dynamic loads, together with low specific weight. This material consists of metal sheets alternating to composite material layers. In the present work, the ILSS (Interlaminar Shear Strength) was evaluated for different types of carbon fibre/aluminium FML, produced varying the layer thickness and the bonding solution of layers. In fact, FMLs consisting of one or two metal sheets (a parameter strictly connected to the layer thickness, as the metal/composite volume fraction was kept at constant value) and bonded with structural adhesive or prepreg resin were considered for this study. The ILSS was determined according to the three-point bending method with short beam specimens. The experimental tests evidenced an effect of the adhesion methodology on the ILSS value, while the layer thickness did not influence the interlaminar strength. The mechanical behaviour after the maximum load point was investigated too, evaluating the trend of the shear stress as a function of the loading nose displacement

Experimental analysis of aluminium/carbon epoxy hybrid laminates under flexural load

Industry needs new materials that present very high structural characteristic, such as high strength, low weight and high damage tolerance. To obtain these characteristics a new class of materials has been introduced: Fibre Metal Laminate (FML); they consist in metal sheets alternated to composite material layers: in such manner, the good characteristics of each constituent material confer the utmost properties to the FMLs. However, the mechanical properties depend, among other factors, on the thickness and the numerousness of the layers constituting the FML, as well as the interface between metal and composite. Therefore, in this paper, the influence of the abovementioned factors on the material answer to flexural load was investigated. In particular, different kinds of laminates were produced varying the layers adhesion and the layers thickness, but maintaining unaltered the metal/composite volume ratio and the total laminate thickness. Then their structural behaviour was investigated through three-point bending test, and it was found that the flexural behaviour was affected by both the investigated factors; in fact, the maximum flexural load diminished incrementing the number of layers and inserting an adhesive layer at the metal/composite interface

Influence of structural characteristics on the interlaminar shear strength of CFRP/Al fibre metal laminates

Abstract High mechanical characteristics, such as impact and fatigue resistance, coupled with low weight can be obtained combining metal sheets and composite laminates; in this way a new hybrid material is obtained: the FML (Fibre Metal Laminate). In the present paper, an analysis of the influence of both composite/metal interface and layer thickness on ILSS (InterLaminar Shear Strength) of a carbon fibre composite and aluminium FML is presented. In particular, two different interfaces were studied: one obtained with a structural adhesive and the other with the prepreg resin; as concerns the layer thickness, both one and two aluminium sheets were considered in laminate stacking, maintaining constant the metal/composite volume ratio. The produced laminates were tested following the short beam three-point bending standard, in such a manner the ILSS properties can be highlighted. From the test carried out for this work it can be concluded that the most influencing factor was the presence of the structural adhesive, while the number of metal sheets was unaffecting

analysis of cfrp al hybrid laminates flexural strength

Abstract Very high mechanical properties, such as high strength, high damage tolerance and low weight, can be reached by coupling composite laminae and metal sheets: in such a manner a new material is obtained: the Fibre Metal Laminate (FML). The diversification of the thickness and the number of layers is suitable to change the structural properties. In order to analyse the influence of these factors on flexural strength, some types of CFRP/aluminium sheet FMLs were manufactured and their structural properties were investigated by means of three-point bending tests. It was discovered that both the studied elements affected the flexural strength of FML; in particular, this mechanical characteristic decreased with the existence of an adhesive film between the metal sheet and the composite plies, whereas it augmented if only one metal sheet was used instead of two ones

hydrogen embrittlement in a 2101 lean duplex stainless steel

Abstract Duplex Stainless Steels (DSSs) are an attractive class of materials characterized by a strong corrosion resistance in many aggressive environments. Thanks to the high mechanical performances, DSSs are widely used for many applications in petrochemical industry, chemical and nuclear plants, marine environment, desalination etc. Among the DSSs critical aspects concerning the embrittlement process, it is possible to remember the steel sensitization and the hydrogen embrittlement. The sensitization of the DSSs is due to the peculiar chemical composition of these grades which, at high temperature, are susceptible to carbide, nitrides and second phases precipitation processes mainly at grains boundary and in the ferritic grains. The hydrogen embrittlement process is strongly influenced by the duplex (austenitic-ferritic) microstructure and by the loading conditions. In this work a rolled lean ferritic-austenitic DSS (2101) has been investigated in order to analyze the hydrogen embrittlement mechanisms by means of slow strain rate tensile tests, considering the steel after different heat treatments. The damaging micromechanisms have been investigated by means of the scanning electron microscope observations on the fracture surfaces

Comparison between long and short beam flexure of a carbon fibre based FML

Abstract A Fibre metal laminate (FML) consists of a stack of metal sheets alternating to composite material layers: in such a manner, the best characteristics of both constituents are combined together. In this work, the flexural behaviour of different kinds of FMLs was investigated. In particular, both long beam and short beam specimens were produced and tested, since the length-to-thickness ratio influences the stress type arising in the material and, consequently, the failure mode. Moreover, the influence of both the composite/metal interface and the thickness of the layers was analysed. It was found that the structural adhesive was deleterious for the flexural strength of the long beam, while it improved the behaviour of the short one. As concerns the thickness and the distribution of the layers, this factor was unaffecting for the short beam specimen, while it was decisive for the long beam one. A micrographic analysis was carried out on the tested specimens, in order to characterize the failure mode. It was found a preponderance of fibre breakage in the long beam, while in the short one the failure of the metal/composite interface was prevailing

Fuzzy-Based Variable Speed Limits System Under Connected Vehicle Environment: A Simulation-Based Case Study in the City of Naples

This paper handles the problem of controlling speed limits on freeways in a connected traffic environment to reduce traffic congestion and improve both the operational and environmental performance of the road network. In order to achieve this objective, we present a Variable Speed Limit (VSL) system that utilizes fuzzy logic, which adjusts the speed limits that connected vehicles must comply with by leveraging traffic data such as vehicle flow, occupancy, and speed obtained from loop detectors installed along the road. To evaluate the effectiveness of the proposed Fuzzy-based VSL system and its potential benefits compared to the conventional rule-based VSL system in terms of traffic congestion and environmental impact, we conducted a simulation analysis using the microscopic traffic simulator, VISSIM. Specifically, three simulation scenarios are taken into account: i) no VSL, where the VSL system is not enabled; ii) Rule-based VSL system, where a typical a decision tree-based system is considered; iii) Fuzzy-based VSL system, where the herein proposed approach is appraised. The results demonstrate that the proposed approach enhances road efficiency by decreasing speed variation, increasing average speed and vehicle volume, and reducing fuel consumption

Integrating tools for an effective testing of connected and automated vehicles technologies

The development of connected and automated driving functions involves that the interaction of autonomous/ automated vehicles with the surrounding environment will increase. Accordingly, there is a necessity for an improvement in the usage of traditional tools of the automotive development process. This is a critical problem since the classic development process used in the automotive field uses a very simplified driver model and the traffic environment, while nowadays it should contemplate a realistic representation of these elements. To overcome this issue, the authors proposed an integrated simulation environment, based on the co-simulation of Matlab/Simulink environment with simulation of urban mobility, which allows for a realistic model of vehicle dynamic, control logics, driver behaviour and traffic conditions. Simulation tests have been performed to prove the reasoning for such a tool, and to show the capabilities of the instrument. By using the proposed platform, vehicles may be modelled with a higher level of details (with respect to microscopic simulators), while the autonomous/automated driving functions can be tested in realistic traffic scenarios where the features of the road traffic environment can be varied to verify in a realistic way the level of robustness of the on-board implemented functions

A microcapillary rheometer for microliter sized polymer characterization

Abstract We report the design of a microcapillary rheometer (μCR) that allows to perform experiments rapidly and in a broad range of shear rates (i.e., from 0.1 to 1000 s−1), using small amounts of material (i.e., just few milligrams). Additionally, multiple measurement parallelization makes it suitable for High-Throughput Rheological Experimentation of polymer melts (HT-Rheo-E). The novel rheometer consists of a set of three cylindrical microcapillaries in which the fluid flows driven by a controlled pressure. A camera, placed at the capillary exit, records the fluid motion to measure its flow rate, from which the fluid viscosity can be determined. The optimization of the setup allowed for reliable and fast viscosity measurements using ca. 10 mg of material. The current work reports the design of the rheometer and validation measurements on several model fluids. The microfabricated μCR is of potential interest for applications in quality control and research where rapid and repeated measurements using limited milligrams of polymer are required, as well as for High-Throughput-Experimentation of complex fluids (e.g., biological systems)