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Fibre reinforced polymer composites (FRPs) are finding increasing usage in many industrial sectors. Adhesive bonding is often the most attractive joining technique for these materials in terms of structural efficiency and cost of manufacture. However, concerns regarding the lack of reliable design methods, the long term ageing behaviour and the difficulties in non‐destructive evaluation and repair of bonded joints has led to a reluctance to use adhesives in primary structures. DERA has been involved in the assessment of adhesive bonding for joining FRPs for many years. This paper focuses on investigations at DERA into the effects that environment and fatigue loading have on the performance of bonded composite joints, and briefly reviews current approaches to strength and lifetime prediction. It is seen that adhesively bonded composite joints can be significantly affected by the service environment, however, this is highly dependent on the joint type and materials involved.

Honeycombs enjoy wide use in various engineering applications. The emergence of additive manufacturing (AM) as a method of customisable of parts has enabled the reinvention of the honeycomb structure. However, research on in-plane compressive performance of both classical and new types of honeycombs fabricated via AM is still ongoing. Several important findings have emerged over the past years, with significance for the AM community and a review is considered necessary and timely. This paper aims to review the in-plane compressive performance of AM honeycomb structures.

This paper provides a state-of-the-art review focussing on the in-plane compressive performance of AM honeycomb structures, covering both polymers and metals. Recently published studies, over the past six years, have been reviewed under the specific theme of in-plane compression properties.

The key factors influencing the AM honeycombs' in-plane compressive performance are identified, namely the geometrical features, such as topology shape, cell wall thickness, cell size and manufacturing parameters. Moreover, the techniques and configurations commonly used for geometry optimisation toward improving mechanical performance are discussed in detail. Current AM limitations applicable to AM honeycomb structures are identified and potential future directions are also discussed in this paper.

This work evaluates critically the primary results and findings from the published research literature associated with the in-plane compressive mechanical performance of AM honeycombs.

The purpose of this paper is to provide an insight into the techniques which are used and developed for adhesive bulk and joint specimens manufacturing.

After a short introduction, the paper discusses various techniques for adhesive bulk and joint specimens manufacturing and highlights their advantages and limitations. A number of examples in the form of different bulk and joint specimens of different types of adhesives are used to show the methods for determining the adhesive's mechanical properties needed for design in adhesive technology. In order to predict the adhesive joint strength, the stress distribution and a suitable failure criterion are essential. If a continuum mechanics approach is used, the availability of the stress‐strain curve of the adhesive is sufficient (the bulk tensile test or the TAST test is used). For fracture mechanics‐based design, mode I and mode II toughness is needed (DCB and ENF tests are used). Finally, single lap joints (SLJs) are used to assess the adhesive's performance in a joint.

Before an adhesive can be specified for an application, screening tests should be conducted in order to compare and evaluate the various adhesion parameters. Properties of adhesives can vary greatly and an appropriate selection is essential for a proper joint design. Thus, to determine the stresses and strains in adhesive joints in a variety of configurations, it is necessary to characterize the adhesive behaviour in order to know its mechanical properties. A great variety of test geometries and specimens are used to obtain adhesive properties. However, for manufacturing of adhesive bulk specimens and joints necessary for use in these tests, properly, moulds should be designed.

The paper summarises the main methods of preparing adhesive bulk and joint specimens and the test methods for determining the mechanical properties needed for design in adhesive technology. Emphasis is given to the preparation of specimens of suitable quality for mechanical property determination and the moulds designed for this purpose.

Among various efforts pursued to produce fuel efficient vehicles, light weight engineering (i.e. the use of low‐density structurally‐efficient materials, the application of advanced manufacturing and joining technologies and the design of highly‐integrated, multi‐functional components/sub‐assemblies) plays a prominent role. In the present work, a multi‐disciplinary design optimization methodology has been presented and subsequently applied to the development of a light composite vehicle door (more specifically, to an inner door panel). The door design has been optimized with respect to its weight while meeting the requirements /constraints pertaining to the structural and NVH performances, crashworthiness, durability and manufacturability. In the optimization procedure, the number and orientation of the composite plies, the local laminate thickness and the shape of different door panel segments (each characterized by a given composite‐lay‐up architecture and uniform ply thicknesses) are used as design variables. The methodology developed in the present work is subsequently used to carry out weight optimization of the front door on Ford Taurus, model year 2001. The emphasis in the present work is placed on highlighting the scientific and engineering issues accompanying multidisciplinary design optimization and less on the outcome of the optimization analysis and the computational resources/architecture needed to support such activity.

This study aims to focus on the optimized design and mechanical properties of gradient triply periodic minimal surface cellular structures manufactured by selective laser melting.

Uniform and gradient IWP and primitive cellular structures have been designed by the optimized function in MATLAB, and selective laser melting technology was applied to manufacture these cellular structures. Finite element analysis was applied to optimize the pinch-off problem, and compressive tests were carried out for the evaluation of mechanical properties of gradient cellular structures.

Finite element analysis shows that the elastic modulus of IWP increased as design parameter b increased, and then decreased when parameter b is higher than 5.5. The highest elastic modulus of primitive increased by 89.2% when parameter b is 6. The compressive behavior of gradient IWP and primitive shows a layer-by-layer way, and elastic modulus and first maximum compressive strength of gradient primitive are higher than that of gradient IWP. The effective energy absorption of gradient cellular structures increased as the average porosity decreased, and the effective energy absorption of gradient primitive is about twice than that of gradient IWP.

This paper presents an optimized design method for the pinch-off problem of gradient triply periodic minimal surface cellular structures.

In this work, the cohesive zone model (CZM) developed by some of the authors to simulate the propagation of fatigue defects in two dimensions is extended in order to simulate the propagation of defects in 3D. The paper aims to discuss this issue.

The procedure has been implemented in the finite element (FE) solver (Abaqus) by programming the appropriate software-embedded subroutines. Part of the procedure is devoted to the calculation of the rate of energy release per unit, G, necessary to know the growth of the defect.

The model was tested on different joint geometries, with different load conditions (pure mode I, mode II pure, mixed mode I/II) and the results of the analysis were compared with analytical solutions or virtual crack closure technique (VCCT).

The possibility to simulate the growth of a crack without any re-meshing requirements and the relatively easy possibility to manipulate the constitutive law of the cohesive elements makes the CZM attractive also for the fatigue crack growth simulation. However, differently from VCCT, three-dimensional fatigue de-bonding/delamination with CZM is not yet state-of-art in FE softwares.

Methods to optimize lattice structure design, such as ground structure optimization, have been shown to be useful when generating efficient design concepts with complex truss-like cellular structures. Unfortunately, designs suggested by lattice structure optimization methods are often infeasible because the obtained cross-sectional parameter values cannot be fabricated by additive manufacturing (AM) processes, and it is often very difficult to transform a design proposal into one that can be additively designed. This paper aims to propose an improved, two-phase lattice structure optimization framework that considers manufacturing constraints for the AM process.

The proposed framework uses a conventional ground structure optimization method in the first phase. In the second phase, the results from the ground structure optimization are modified according to the pre-determined manufacturing constraints using a second optimization procedure. To decrease the computational cost of the optimization process, an efficient gradient-based optimization algorithm, namely, the method of feasible directions (MFDs), is integrated into this framework. The developed framework is applied to three different design examples. The efficacy of the framework is compared to that of existing lattice structure optimization methods.

The proposed optimization framework provided designs more efficiently and with better performance than the existing optimization methods.

The proposed framework can be used effectively for optimizing complex lattice-based structures.

An improved optimization framework that efficiently considers the AM constraints was reported for the design of lattice-based structures.

Fibre-reinforced additive manufacturing (FRAM) with short and continuous fibres yields light and stiff parts and thus increasing industry acceptance. High material anisotropy and specific manufacturing constraints shift the focus towards design for AM (DfAM), particularly on toolpath strategies. Assessing the design-property-processing relations of infill patterns is fundamental to establishing design guidelines for FRAM.

Subject to the DfAM factors performance, economy and manufacturability, the efficacy of two conventional infill patterns (grid and concentric) was compared with two custom strategies derived from the medial axis transformation (MAT) and guided by the principal stresses (MPS). The recorded stiffness and strength, the required CPU and print time, and the degree of path undulation and effective fibre utilisation (minimum printable fibre length) associated with each pattern, served as assessment indices for different case studies. Moreover, the influence of material anisotropy was examined, and a stiffness-alignment index was introduced to predict a pattern’s performance.

The highest stiffnesses and strengths were recorded for the MPS infill, emphasising the need for tailoring print paths rather than using fixed patterns. In contrast to the grid infill, the concentric infill offered short print times and reasonable utilisation of continuous fibres. The MAT-based infill yielded an excellent compromise between the three DfAM factors and experimentally resulted in the best performance.

This constitutes the first comprehensive investigation into infill patterns under DfAM consideration for FRAM, facilitating design and processing choices.

Adhesively bonded joints are gaining importance in the structural joining processes competing against welding and bolting processes. However, long-term behaviour of adhesively bonded joints is still an open question. Due to the increasing interest in adhesively bonded joints, mainly in the transports industry, there is a need to deep the knowledge about the fatigue behaviour of adhesive joints with metallic substrates allowing the development of reliable joints to resist cyclic loadings. The paper aims to discuss these issues.

An experimental research aiming at characterizing the fatigue behaviour of adhesively bonded aluminium substrates is presented in this paper, covering both fatigue crack propagation and global S-N behaviours. Double cantilever beam (DCB), end notch flexure (ENF) and double lap joints (DLJ) specimens built using the AA6061T651 substrate and epoxy adhesive were used to evaluate the pure modes I and II fatigue crack propagation rates and the S-N fatigue behaviours.

DCB and ENF specimens allowed the formulation of pure modes I and II fatigue crack propagation laws including the propagation thresholds. DLJs showed higher static shear strength than recommended by the manufacturer for aluminium substrates, but fatigue resistance of the DLJs was lower than suggested by the manufacturer. The fatigue damage process in the DLJs was dominated by a fatigue crack initiation process.

A consistent fatigue research on adhesively bonded aluminium substrates is presented covering in the same study aspects of fatigue crack propagation and fatigue crack initiation. Data reduction schemes involving both numerical and analytical procedures were followed. Proposed work constitutes a rigorous basis for future fatigue prediction models developments.

The purpose of this study is to create a mathematical model, a numerical algorithm and a computer program for studying the vibration of composite pipelines based on the theory of beams used in the oil and gas industry, agriculture and water management, housing and communal services and other areas.

A mathematical model of vibration of a viscoelastic pipeline based on the theory of beams with a pulsating fluid flowing through it was developed. Using the Bubnov-Galerkin method, based on the polynomial approximation of deflections, the problem is reduced to the study of systems of ordinary integro-differential equations, the solution of which is found by a numerical method. A computational algorithm was developed for solving problems of vibrations of composite pipelines conveying pulsating liquid.

The stability and amplitude-time characteristics of vibration of composite pipelines with a pulsating fluid flowing in it are studied for wide range of changes in the parameters of deformable systems and fluid flow. The critical velocities of fluid flow at which the viscoelastic pipe loses its rectilinear equilibrium shape are found. The effect of singularity in the kernels of heredity on the vibrations of structures with viscoelastic properties was numerically studied. It is shown that with an increase in the viscosity parameter of the pipeline material, the critical flow velocity decreases. It was determined that an increase in the value of the fluid pulsation frequency and the excitation coefficient leads to a decrease in the critical velocity of the fluid flow. It was established that an increase in the parameters of the Winkler foundation and the rigidity parameter of the continuous layer leads to an increase in the critical flow velocity.

The study of the vibration of pipelines made of composite materials is of great theoretical and applied interest. The solution to this problem is an effective application of the theory of viscoelasticity to real processes. Therefore, the methods and problems of pipeline vibrations attract much attention from researchers. This study is devoted to solving the above problems and therefore its subject is relevant. The paper considers the results of numerical simulation of the processes of vibration of a composite pipeline based on the theory of shells during the flow of a pulsating liquid through it. A mathematical model of vibration of a composite pipeline was developed. A computational algorithm was developed for solving problems of vibrations of composite pipelines conveying pulsating liquid.