Search

Herein, the effect of anisotropy on the thermal response of two carbon fibre-reinforced composite samples (unidirectional and cross-ply) is studied using step-heating thermography. An objective methodology is developed for qualitative and quantitative analyses of flaws using their aspect ratios and signal-to-noise ratio (SNR). The procedure uses principal component analysis, Gaussian filter, and binarisation for marking the candidate flaw locations. After experimenting on different heating/cooling regimes, single-phase cooling was nominated to further the study. It is found that short thermal excitations reveal surface flaws while increasing the heating period improves the visibility of deeper flaws. Anisotropy, due to fibre alignment, affects the aspect ratio of flaws, distorts their shape, and conjoins clustered flaws. In contrast, SNR values seem to be insensitive to anisotropy. The proposed method offers a quick and simple procedure for post-processing thermal images and highlights the implications of anisotropy therein.

Determination of the early-age compressive strength of concrete is essential for quality assurance, safety, and economy of construction projects. Due to manual operation on construction site, conventional maturity meters are not efficient for live monitoring of the early-age concrete strength. Higher levels of automated and computerised improvements have been made possible by recent developments in wireless communications, sensor technologies, and data processing methods across the construction industry. For real-time monitoring of the early-stage concrete strength, the current study presents an innovative Internet of Things (IoT)-enabled system developed by concrete data sensors (CDS), an Australian-owned private business. The CDS sensor system (the system) communicates with temperature sensors via long-range wide-area network and is linked to a cloud-based platform for data storage. The suggested system’s effectiveness was assessed using three concrete mixtures and developed maturity relationships. It was observed that the predicted early-age compressive strength of the mixes matches well with the actual compressive strength and that the system can effectively automate the characterisation of maturity.

Herein, the general constitutive equation of bi-phasic materials equipped with orientation tensor is presented in direct notation. The formulation is refined by some correction factors specific to ...

The aim of the current work was to illustrate the effect of the fibre area correction factor on the results of modelling natural fibre-reinforced composites. A mesoscopic approach is adopted to represent the stochastic heterogeneity of the composite, i.e. a meso-structural numerical model was prototyped using the finite element method including quasi-unidirectional discrete fibre elements embedded in a matrix. The model was verified by the experimental results from previous work on jute fibres but is extendable to every natural fibre with cross-sectional non-uniformity. A correction factor was suggested to fine-tune both the analytical and numerical models. Moreover, a model updating technique for considering the size-effect of fibres is introduced and its implementation was automated by means of FORTRAN subroutines and Python scripts. It was shown that correcting and updating the fibre strength is critical to obtain accurate macroscopic response of the composite when discrete modelling of fibres is intended. Based on the current study, it is found that consideration of the effect of flaws on the strength of natural fibres and inclusion of the fibre area correction factor are crucial to obtain realistic results.

To improve the mechanical properties of cast aluminium alloys several post‐heat treatments are known. However, these treatments cannot directly be transposed to additively via selective laser melting manufactured aluminium alloys, e. g., aluminium‐silicon‐magnesium (AlSi10Mg). Therefore, this study aims to determine suitable post‐heat treatments to optimise the mechanical properties of SLM‐built AlSi10Mg specimen. The influence of various post‐heat treatment conditions on the material characteristics was examined through hardness and tensile tests. The findings indicate that the Vickers hardness and ultimate tensile strength could not be improved via secondary precipitation hardening, whereas the fracture elongation shows a value which is distinctly higher than the values of a comparable cast alloy. Solution annealing at 525 °C reduces the hardness and the ultimate tensile strength by about 40 % and increases the fracture elongation three times. A subsequent precipitation hardening allows recovery of 80 % of the as‐built hardness, and 90 % of the previous ultimate tensile strength combined with maintaining an improved fracture elongation of about 35 % compared to the respective as‐fabricated condition.

This chapter introduces the six basic steps needed to design and make a fibre-reinforced composite (FRC): (1) fibre and matrix selection; (2) mould preparation; (3) layup and consolidation; (4) curing (and post-curing); (5) demoulding; and (6) post-processing (finishing). These six steps are considered using a simple wet layup process for a flat unidirectional (UD) composite. The mechanical performance of the composite is estimated based on the rule of mixtures (RoM), inverse rule of mixtures (IRoM) and Kelly-Tyson (KT) models from Chap. 2. A description of the wet layup process is offered and discussed in the context of the options available to a composite fabricator. The chemical crosslinking processes for polyester, vinylester and epoxy are presented. Consideration is given to demoulding the FRC and to the post-processing options. The use of gelcoat, flow coat and paint are mentioned in the context of a broader discussion on surface finishing of FRC. The outcome of the chapter is a step-by-step design and manufacturing method that is easily replicated.

So far, this book has focused on flat, planar laminates in order to simply and easily illustrate composite design and manufacture considerations. However, creating most composite structures (or parts) requires a mould. This chapter considers composite design in the context of part mouldability (i.e. design for manufacture, DFM), and offers the composite designer some guidance on mould design and construction. In terms of part mouldability, special attention is given to draft angles (and undercuts), surface textures and sharp corners. Mould design and construction are examined in the context of mould durability; speed and ease of construction; and the mould tool fabrication cost. A step-by-step mould-making process is presented to enable the reader to better understand moulding considerations for laminates. A simple composite part (a frisbee) is then moulded to illustrate the fabrication process.

A selection of simple composite design (mechanics) equations were introduced in Chap. 2 to enable prediction of the mechanical properties of fibre-reinforced composites (FRCs). The rule of mixtures (RoM) and inverse rule of mixtures (IRoM) expressions were introduced for elastic moduli estimation, whilst longitudinal strength was considered via the Kelly-Tyson (KT) model. Chapters 3 and 4 then introduced wet layup, and vacuum bagging and prepreg moulding methods for composite manufacture. A carbon fibre-reinforced panels was fabricated using similar constituents (i.e. Open image in new window carbon fibres in an epoxy matrix) for each fabrication method. This chapter builds on these earlier chapters via a comparison of design (mechanical property) estimates and experimental data. Tensile tests are performed on multiple specimens cut from each of the panels. This chapter provides guidance on the accuracy of design estimates and offers support for the typical (rule of thumb) volume fractions suggested in Chaps. 3 and 4 for each manufacturing approach.

The concept of fibre-reinforced polymer composites is introduced in this chapter. Most fibre-reinforced composites (FRCs) comprise two constituent materials (known as phases): a fibre phase and a matrix phase. It is noted that thermosetting matrices are far more frequently used for FRCs than their thermoplastic counterparts. An overview of the three most commonly used thermosetting matrices (i.e. unsaturated polyester, vinylester and epoxy) is provided. Available fibre types and forms are considered. The representative mechanical properties for the most common fibre types (glass, carbon and aramid) are presented and compared to traditional materials.

This chapter considers the manufacture of hollow sections. Mandrel lamination (wrapping) and bladder moulding are described and then used to create composite tubes. A step-by-step guide to tube manufacture is presented for prepreg moulding, but the fabrication methods introduced are more widely applicable (and hence, can be adapted for use in wet layup processes). Whilst the focus is on cylindrical tubes, the fabrication process can be simply modified to create square or rectangular hollow sections or more complex tubular structures. A helical spring and a bicycle handlebar are used as more complex examples. Demoulding methods for mandrel wrapped tubes are discussed. A specific focus is given to mechanical extraction and thermal (heating and cooling) mechanisms. The concept of mouldless composite construction is introduced. The importance of a mandrel’s coefficient of thermal expansion is considered in the context of demoulding using thermal methods.

This chapter addresses the mechanical properties of a fibre-reinforced composite (FRC). The focus is on calculation of the elastic modulus and strength for unidirectional FRCs using the rule of mixtures expressions, but woven and random fibres are also considered. A unidirectional FRC exhibits anisotropic behaviour. It is stiffest and strongest in the fibre direction but is relatively compliant and weak in the transverse orientation. Woven structures provide similar mechanical properties in their axial (longitudinal) and transverse orientations, whilst random fibre composites simulate in-plane isotropic behaviour. The effect of the fibre and matrix properties on the structural behaviour of a composite is investigated in the context of fibre volume fractions (and weight fractions), assuming no voids and perfect fibre-matrix adhesion.

The present study unravels the deformation mechanisms observed during the static inclined compression of re-entrant honeycomb (RH) auxetic structure. A pushover Riks analysis is conducted by facing a rigid plate towards the structure at various angles. A new ‘plastic hinge tracing method’ is introduced to systematically extract the micro deformation mechanisms under inclined loading. The identified modes are related to the macro deformation regime and the overall mechanical response of the RH structure. Moreover, their relation to various measures of efficiency is elaborated. It is shown that a transition stage emerges under inclined loading, which delays achieving the peak energy efficiency. The overall energy dissipation decreases in the inclined cases but interestingly, the performance of the RH structure does not deteriorate. Namely by maintaining a low crushing force under inclined loads, the trade-off of low energy dissipation is balanced and a lower impact is anticipated. Finally, the similarities between the transition stage and the macro modes are highlighted and further directions for investigation are proposed.

In the current study, five cases of fiber distributions are considered in a fiber-reinforced composite: one random, three partitioned (one uniform and two biased cases), and one aligned case for benchmarking. The finite element method and the principal component analysis were used to interpret the results of orientation tensors and detect any possible clusterings of a representative volume element (RVE). The obtained effective conductivity values were extensively controlled by the fiber volume fraction. At the same time, the uniformity of the random distributions could be recognized. Cross-partition resistance was also detected for the partitioned cases which contributed to a reduced heat transfer capability. Finally, the clustering indexes did not show a direct correlation with the conductivity results, and thus a case-by-case investigation is recommended to consider the anisotropic aspects of a microstructure.

Depth-sensing indentation tests are used to characterize non-conventional materials, such as biomaterials, which normally require particular considerations in terms of specimen preparation. The force-depth measurements during the test reveals valuable information about the material which can be used to obtain the elastic modulus of the sample. Analytical 2D formulas are available in the literature which incorporate a scale factor to establish a proper relationship between the elastic modulus and the force-indentation data. Finite element analysis in 3D was used to simulate the indentation test results, propose a modified scale factor for the analytical solution, and to make a comparison between the modified and original scale factors. The numerical results revealed that the 2D formulation produces closer values to those of the 3D simulations at higher aspect ratios. Additionally, in order to consider the effects of the substrate, two extreme values for the scale factor are proposed.

In the current study, two extreme cases are considered for the dispersion of carbon nanotubes(CNTs) in a polymeric matrix: randomly-oriented and randomly-aligned. The representative volume element (RVE) is used to represent the composite material consisting of epoxy resin matrix and CNT-reinforcement. The finite element method acts as the computational tool to conduct the simulations and investigate the effective parameters, i.e., the influence of the aspect ratio and the orientation, on the thermal conductivity of the matrix. A Fortran subroutine was used for both generation and analysis of the models by means of the MSC Marc finite element package and a Python script was used for the sensitivity analysis. The results indicate that optimum performance of the CNTs in terms of thermal conductivity can be reached by orienting them along the temperature gradient whereas a random distribution improves the conductivity by a smaller magnitude.

The current study presents a high-performance steel plate shear wall system, which is capable of dissipating large amounts of energy. A specific arrangement of perforations in the infill panel as well as the adjacent horizontal boundary elements is proposed. The aim was to increase the ductility of the system by inhibiting the pre-mature failure of the critical structural components. To this end, a sacrificial structural element, i.e., the steel panel, was implemented into the frame system to adopt the main role of energy dissipation. To allow an extensive development of the plastic field in the steel panel, perforated areas were designated at each of its corners. Furthermore, the concept of web-reduced beam sections was applied. Two other patterns and a benchmark case were also introduced for comparison. It was shown that the proposed system excels in energy dissipation for the price of slight initial stiffness loss. Furthermore, the synergistic effect of the suggested modifications delayed the initiation of inelastic deformations in the surrounding structural members. Thus, these components and their connections remain protected under extreme loading regimes. One could take advantage of the proposed arrangement if harsh loading conditions are plausible.

The present study focuses on the deformation mechanisms of re-entrant honeycomb auxetic structures under inclined loading. An auxetic finite element prototype is compressed by a rigid plate during a static Riks analysis. Analysing the deformation response of the structure has revealed that a new transitional deformation stage emerges that highly restricts the elastic response. This new macro stage consists of consecutive micro stages of plateau-densification (yielding-hardening) that corresponds to a highly localised deformation mode, and alters the mechanical response in the following macro stages.

As an effective lateral resisting system, a steel plate shear wall (SPSW) should provide adequate ductility and dissipate energy while protecting its boundary elements (BEs). Herein, the failure modes of a recently-introduced design for SPSWs (a perforated panel with a web-reduced beam section) was investigated. The aim was to control the failure mechanism of this arrangement by various geometrical modifications. To obtain a high-performing design, the interaction of the structural components was studied in terms of plastic strain distribution, ductility, strength, and stiffness. To this end, a finite element prototype was populated for a range of geometrical parameters. The analyses were carried out by varying the panel and beam perforation sizes; then, one excelling combination was further challenged by altering its panel thickness and the frame aspect ratio. The model successfully distinguished between three common failure modes and provided an interesting insight into the causality of the failure mechanisms. It was found that the size of the perforations in the panel and the beam, and the size of the horizontal boundary elements could be manipulated to obtain the desired mechanism. Therein, the tensile failure of the panel was dominant where a plastic band formed across the panel and protected the vertical BEs and their connections. Moreover, the model outperformed its imperforate counterpart in terms of hysteresis ductility and absorbed energy (by about 250%) due to the increased engagement of the structural members. Finally, the findings were summarised into some practical recommendations for improving the design of the proposed arrangement.

In the current study, the representative volume element (RVE) is used to model randomly generated nanocomposite structures consisting of carbon nanotubes (CNTs) embedded in an epoxy resin matrix. The finite element Method is utilized for numerical simulations and investigation of the influential parameters on the generated RVEs. In order to automatize the whole procedure - fromgenerating the finite element models to conducting the analyses - a subroutine-based programming approach is adopted using the MSC Marc finite element package and Fortran programming language. The simulations can successfully predict the increase in thermal conductivity of CNT-reinforced nanocomposites by increasing the fiber volume fraction.

A parametric finite element analysis was carried out to investigate the sensitivity of the effective thermal conductivity of fibers to orientation clustering. Randomly-positioned fibers with von Mises orientation distributions were used in different considerations and volume fractions to generate the dispersion in a partitioned representative volume element. It was found that increasing the fiber volume fraction increases the thermal conductivity; this improvement is significant specially when a preferred orientation is detected with a cluster-free state. Further reinforcement of the composite is made possible by increasing the maximum principal value of the orientation tensor provided that the principal direction is set accordingly. Furthermore, clustering index does not seems to be affected by volume fraction when an equal distribution is present in partitions.

This chapter briefly reviews two important mathematical topics in the scope of the finite element context. To solve a finite element problem means finally to solve a system of equations. This is, in the simplest case, a linear system of equations and this chapter introduces two simple solution strategies, i.e. the Gaussian elimination and the inversion of the coefficient matrix. The second topic covers the analytical and numerical integration which is needed, for example, to evaluate the elemental stiffness matrix and the column matrix of equivalent nodal loads.

The finite element analysis is used to investigate the sensitivity of the effective transverse thermal conductivity of polymeric composites reinforced with Manila hemp fibers in terms of their degree of saturation. It is predicted that the hierarchical structure of the fiber bundle will highly magnify the rate of water absorption and in consequence, the effective transverse thermal conductivity of the composite is altered. This influence is quantized in terms of the volume fraction of the fiber bundle and the lumen to produce a homogenized representative continuum. It was found that increasing the fiber volume fraction in a dry medium results in a decrease in the thermal conductivity whereas an increase of conductivity will be evident in a wet condition. Furthermore, the increase in the volume fraction of the lumen enhances the thermal conductivity by retaining more water during saturation which supports the developed hypothesis.

There is no unique way of handling a complicated modeling task. However, some typical procedures are in common between various methods.

Considering the fact that Marc is based on the Fortran programming language, not only is the basic knowledge of the language is indispensable, but becoming familiar with advanced features will definitely improve the structure of the code. In this chapter, a comprehensive review of the advanced capabilities of the Fortran language will be presented.