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In the preliminary stage of the industrial design, the structural analysis of the components made of composite materials is generally difficult to carry out for aircraft structures having complex three-dimensional geometry. More importantly, in the case of composite structures, the lay-up process creates a particular distribution of the material properties that is challenging to simulate in a virtual environment. This research work is, therefore, focused on the use of the finite element method for the numerical analysis and the structural redesign of the bulkhead and flap aircraft components. In particular, the numerical results obtained in this work are the stress and strain fields of these mechanical components. The redesign and the structural optimization of these two mechanical components are performed employing a simple numerical procedure. For this purpose, the quality of the stress and strain fields obtained by performing numerical experiments is evaluated considering failure criteria suitable for composite structures. Subsequently, the analysis developed in this study is used for determining the performance of the material as well as the number and orientation of the plies selected for the composite components. The verification process performed in this work, on the other hand, consisted of a comparative analysis with the same aerospace components made of isotropic and anisotropic materials. The numerical results found are compared with the experimental results available for the aerospace components that are geometrically and functionally similar to the bulkhead. In general, a good agreement is found in the comparison between the numerical and experimental results. [ABSTRACT FROM AUTHOR]

Laser ultrasonic non-destructive testing is widely used for the inspection of mechanical structures. This method uses the propagation of ultrasonic guided waves (UGW) in the media. It has been demonstrated that the addition of a thin composite layer between the laser source and the structure for inspection is necessary. Consequently, this composite is an optoacoustic transducer composed of an absorption material as carbon for inclusions and an expanding material as an elastomer for the matrix. Thus, optimal fabrication of this composite should enable the amplification of the signal for inspection. Indeed, experimental research has demonstrated that variation in the volume fraction of carbon inclusions, their shape and the nature of the matrix affect the amplification of the signal directly. The aim of this study is to analyse the wave propagation in particulate viscoelastic composites by a dynamic self-consistent approach. [ABSTRACT FROM AUTHOR]

• This research reports the fatigue behaviour of new composite materials produce by additive manufacturing. • The results showed that carbon fibre isotropic layers had the higher ultimate tensile stress with 165 MPa. • Fibre length and orientation, properties of the composite matrix, and interfacial properties have an important effect in the fatigue behaviour. • This research shows the potential of AM composite material for engineering applications. In additive manufacturing (AM), the thermoplastic parts made by FDM present lack of strength and low stiffness, as required for fully functional and load-bearing parts. Due to this restriction, a new technology to reinforce with fibres the thermoplastic filaments was developed over the last years. Continuous fibre reinforced thermoplastic composites (CFRTPC) printers are elevating this technology to a whole new level in terms of efficient production and mechanical properties. Static mechanical properties, as well as fatigue behaviour, were studied since in these types of loads a wide range of engineering dynamic applications can be envisaged. Tensile tests were performed to characterise the static mechanical properties. Fatigue tests were done to analyse the durability behaviour of the FDM composite materials, and the fracture surface was analysed by SEM microscopy. The results showed that carbon fibre isotropic layers had the higher ultimate tensile stress, with 165 MPa. From fatigue tests, stress vs. number of cycles curves (S vs N f) in the temporary life zone were obtained. It was observed from the results that specimens with nylon matrix, triangular filling pattern and matrix density of 20%, reinforced with carbon fibre at 0-degrees, showed better fatigue performance, increasing significantly the number of cycles before specimen rupture. The parameters for the Basquin's equation were found (S = A · N f b ), with A = 206 MPa, and b = −0,039. Accordingly, mechanical characterization of continuous fibre reinforced thermoplastic composites was investigated, which showed the potential use as a composite material for engineering applications. [ABSTRACT FROM AUTHOR]