Three-dimensional needle-punching for composites – A review

The current literature on three-dimensional (3D) needle-punched composites tends to address the aspects of preforms fabrication and composites characterization respectively. This paper aims to bring together these two aspects to provide readers with a comprehensive understanding of the subject of 3D needle-punched reinforcements for composites. Consequently, this paper contains a detailed outline of the current state of 3D needle-punched technology for manufacturing advanced composite preforms. Properties of 3D needle-punched composites and some of the predictive models available for determining these properties are also reviewed. To conclude, a number of current and potential applications of 3D needle-punched preforms for engineering composites are highlighted, and issues impeding the use of 3D needle-punched composites are also summarized.     

Flax fibre and its composites – A review

In recent years, the use of flax fibres as reinforcement in composites has gained popularity due to an increasing requirement for developing sustainable materials. Flax fibres are cost-effective and offer specific mechanical properties comparable to those of glass fibres. Composites made of flax fibres with thermoplastic, thermoset, and biodegradable matrices have exhibited good mechanical properties. This review presents a summary of recent developments of flax fibre and its composites. Firstly, the fibre structure, mechanical properties, cost, the effect of various parameters (i.e. relative humidity, various physical/chemical treatments, gauge length, fibre diameter, fibre location in a stem, oleaginous, mechanical defects such as kink bands) on tensile properties of flax fibre have been reviewed. Secondly, the effect of fibre configuration (i.e. in forms of fabric, mat, yarn, roving and monofilament), manufacturing processes, fibre volume, and fibre/matrix interface parameters on the mechanical properties of flax fibre reinforced composites have been reviewed. Next, the studies of life cycle assessment and durability investigation of flax fibre reinforced composites have been reviewed.     

Measuring the rate-dependent mode I fracture toughness of composites – A review

Composite materials are often subjected to mechanical impact causing delamination. For quasi-static loading, measuring the mode I fracture toughness has been standardized. However, for high-rate loading, additional challenges arise. Consequently, no standard test has yet been defined for measuring the mode I fracture toughness under high rates of loading. This article therefore reviews candidate tests for measuring the high-rate mode I fracture toughness. Strength and weaknesses of different specimen designs and test setups are shown. Different approaches to measuring crack growth and loads are presented. The different approaches are compared and recommendations are provided for measuring the mode I fracture toughness of composites under high rates of loading.     

Reliability in composites – A selective review and survey of current development

As a response to the rampant increase in research activity within reliability in the past few decades, and to the lack of a conclusive framework for composite applications, this article attempts to identify the most relevant reliability topics to composite materials and provide a selective review. Available reliability assessment methods are briefly explained, referenced and compared within an unified formulation. Recent developments to confer efficiency in computing reliability in large composite structures are also highlighted. Finally, some general conclusions are derived along with an overview of future directions of research within reliability of composite materials and their influence on design and optimization.     

A review of bast fibres and their composites. Part 2 – Composites

Bast fibres are defined as those obtained from the outer cell layers of the stems of various plants. The fibres find use in textile applications and are increasingly being considered as reinforcements for polymer matrix composites as they are perceived to be “sustainable”. The fibres are composed primarily of cellulose which potentially has a Young’s modulus of ～140 GPa (being a value comparable with man-made aramid [Kevlar/Twaron] fibres). The plants which are currently attracting most interest are flax and hemp (in temperate climates) or jute and kenaf (in tropical climates). Part 2 of this review will consider the prediction of the properties of natural fibre reinforced composites, manufacturing techniques and composite materials characterisation using microscopy, mechanical, chemical and thermal techniques. The review will close with a brief overview of the potential applications and the environmental considerations which might expedite or constrain the adoption of these composites.     

Mechanics of mechanically fastened joints in polymer–matrix composite structures – A review

As the applications of advanced composite structural materials continue to increase, so does the need to understand the mechanical behavior of mechanically fastened joints in such structures. The most recent and relevant review article on this subject was published more than a decade ago, but it was restricted to stress analysis and strength prediction of mechanically fastened joints in fiber-reinforced plastics. The present article attempts a more comprehensive review of recent literature in the broader area of mechanics of mechanically fastened joints in polymer–matrix composite structures. Since experimental characterization has traditionally played such a fundamental role in such studies, the article begins with a review of relevant mechanical test methods and standards. This is followed by a discussion of the mechanics aspects of design, including joint design methodologies, considerations of the influence of geometric effects, and fastener preload selection. The remaining sections are devoted to failure modes such as bearing failure, failure prediction for both statically and dynamically loaded joints, time-dependent joint preload relaxation, the effects of temperature and moisture on joint strength and failure, and non-destructive evaluation techniques for monitoring the joints. Finally, comments are offered regarding the most important remaining problems in this area, and recommendations for future work.     

Obsolescence – A review of the literature

Technology progress and fierce competitiveness between manufacturers creates intense pressues to innovatively develop and sell new products. These products could be household or industrial items, such as telephones, computers, machines, robots, unmanned aerial vehicle (UAV), motors, industrial processes, electronic devices, tools, and spare parts in general. The technological progress implies the use of the word “obsolescence.” The new products have higher performance metrics compared to the older units, such as reliability, resilience, memory capacity, improved material, precision, artificial intelligence, lower energy consumption, ergonomics, and safety. Therefore, obsolescence became a paradox in our daily life and industry. This paper presents a literature review of the main published works on obsolescence (1976–2020). Its typologies, consequences and replacement strategies are illustrated.     

A review of bast fibres and their composites. Part 1 – Fibres as reinforcements

Bast fibres are defined as those obtained from the outer cell layers of the stems of various plants. The fibres find use in textile applications and are increasingly being considered as reinforcements for polymer–matrix composites as they are perceived to be “sustainable”. The fibres are composed primarily of cellulose which potentially has a Young’s modulus of ～140 GPa (being a value comparable with man-made aramid [Kevlar/Twaron] fibres). The plants which are currently attracting most interest are flax and hemp (in temperate climates) or jute and kenaf (in tropical climates). This review paper will consider the growth, harvesting and fibre separation techniques suitable to yield fibre of appropriate quality. The text will then address characterisation of the fibre as, unlike man-made fibres, the cross section is neither circular nor uniform along the length.     

The potential of knitting for engineering composites—a review

Current literature on knitted composites tends to address the aspects of manufacture and characterisation separately. This paper aims to bring together these two sets of literature to provide the reader with a comprehensive understanding of the subject of knitted composites. Consequently, this paper contains a detailed outline of the current state of knitting technology for manufacturing advanced composite reinforcements. Selected mechanical properties of knitted composites, and some of the predictive models available for determining them are also reviewed. To conclude, a number of current and potential applications of knitting for engineering composites are highlighted. With a comprehensive review of the subject, it is believed that textile engineers would be able to better understand the requirements of advanced composites for knitting, and, by the same token, composites engineers can have a better appreciation of the capability and limitations of knitting for composite reinforcement. This should lead to more efficient usage and expanded application of knitted composites.     

A novel processing scheme for core – shell nano composites using controlled polymer adsorption

 A new processing scheme has been developed for the preparation of core-shell structured composite particles that can be used as building blocks for the fabrication of nanocomposites [1]. The scheme is a two stage coating process utilizing controlled polymer adsorption and bridging in which a layer of nano sized particles is bridged onto submicron sized core particles. The coating process is monitored using electrokinetic techniques as well as SEM. The controlled coating process was used also to prepare multilayer nanocomposites. The application of the coating process to concentrated suspensions (15 volume percent) required in ceramic processing was shown to be feasible. Ceramic compacts were successfully prepared using pressure filtration methods and tested for their green density and flexibility. Received: 18 October 1998/Revised and accepted: 1 December 1998     

Tribology of electroless nickel coatings – A review

Electroless coating is different from the conventional electrolytic coating as the former does not require any electricity for its operation. The advantages include uniform coating and also nonconductive materials can be coated. Electroless nickel coatings possess splendid tribological properties such as high hardness, good wear resistance and corrosion resistance. For this reason, electroless nickel has found wide applications in aerospace, automobile, electrical and chemical industries. Quest for improved tribological performances has led many researchers to develop and investigate newer variants of electroless nickel coatings like Ni–W–P, Ni–Cu–P, Ni–P–SiC, Ni–P–TiO₂, and so on. Also the enhancement of tribological characteristics through modification of the coating process parameters has remained a key point of interest in researchers. The technological advancement demands the development of newer coating materials with improved resistance against wear and tear. Electroless nickel has shown huge potential to fit in that space and so the study of its tribological advancement deserves a thorough and exhaustive study. The present article reviews mainly the tribological advancement of different electroless nickel coatings based on the bath types, structure and also the tribo testing parameters in recent years.     

Modeling tribocorrosion of passive metals – A review

Tribocorrosion is a material degradation phenomenon resulting from interactive effects between wear and corrosion. It is commonly found in engineering applications (e.g. biomedical implants and marine equipment) which involve relative motion of contacting metals in a corrosive environment. In this study, models describing tribocorrosion of passive metals in sliding contacts were reviewed. Different categories of models (two-body or three-body contact models, lubricated tribocorrosion model, empirical models, multi-degradation models) were found in the literature. Through the identification of relevant chemo-mechanical degradation mechanisms, robust analytical expressions accurately predicting the overall material loss in tribocorrosion have been developed. Numerical methods have been used to describe time dependent transitions in tribocorrosion. Possibilities and limits of the proposed models in the literature as well as future trends are discussed in this review.     

Pressure infiltration processes to synthesize metal matrix composites – A review of metal matrix composites,the technology and process simulation

Metal matrix composites (MMCs) acquire their improved physical and mechanical properties through the careful reinforcement of their matrices by a variety of light but strong and stable reinforcement materials. The pressure infiltration process (PIP) is one of the most important techniques used for making MMCs with a high reinforcement content in which a molten metal or alloy is injected and solidified in a mold packed with continuous or discontinuous reinforcement materials. Several factors affect the quality of MMCs made by this process. These include, but are not limited to, the reinforcement type, preform geometry, applied pressure and pressure control, as well as the transport phenomena of the molten metal. This paper presents a review of the various aspects of MMCs, the process in terms of the technological details, the latest developments in the reinforcement materials used and the simulation models developed for pressure infiltration manufacturing of MMCs.     

Structural assessment of railway axles – A critical review

The safety assessment of railway axles is based on a two-stage approach: fatigue strength design and regular inspections which, in terms of a general safety philosophy refer to safe-life and damage tolerance concepts. Starting with a recent failure case, a broken axle of a German high speed train, a discussion is presented on issues of both safety levels. These include ideas for finite life design, the treatment of in-service effects on the fatigue strength due to flying ballast damage and corrosion pits, the effect of corrosion on fatigue crack initiation and propagation, potential effects of non-metallic inclusions in steels, the way to detect them by quality control measures and reliability aspects of non-destructive testing with respect to the detection of fatigue cracks. Proposals are made how the safety level could be further improved.     

Mechanical properties of cement-treated aggregate material – A review

Cement-treated aggregate material (CTAM) is a traditional material applied in road bases and sub-bases. Its mixture proportioning design method applied in the last decades is tentative, time-consuming and cost-effective. There is no advanced technique to design the mixture proportioning of CTAM so far. Therefore, the problem of designing a CTAM mixture is the lack of an effective procedure that allows predicting its mechanical properties from mixture parameters like the mix composition and the characteristics of components. For cement concrete and asphalt concrete such prediction techniques already exist.This paper herein reviews the influence of mixture variables on the mechanical properties of CTAM. These properties include the unconfined compressive strength (UCS), the tensile strength and the elastic modulus. It was found that the UCS is normally taken as an important quality indicator of CTAM. Variables influencing the UCS, such as cement content, curing time, degree of compaction and so on, play different roles to determine the performance of CTAM. Models to predict the tensile strength and the elastic modulus are always correlated to the UCS. Evidence may be given that prediction models for the mechanical properties of CTAM may be established on basis of mixture parameters.     

The Master SN curve approach – A hybrid multi-scale fatigue simulation of short fiber reinforced composites

Typical short fiber reinforced composites (SFRCs) components have a different statistical distribution of orientation of fibers at different points leading to different static and fatigue behavior at different locations across the component. To link component-scale calculations with this variability of fiber orientations, each element in the FE model is modeled as a Representative Volume Element (RVE); the static and fatigue properties must be calculated for each of these elements. While there are established methods to estimate the static properties, there are none for the fatigue properties. A hybrid (combination of micromechanics and tests) and multi-scale (damage in micro-scale linked to macroscale fatigue properties) method of predicting the SN curve for every point in a short fiber composite has been developed. This proposed method is based not only on tests but on a combination of manufacturing simulation, tests and multi-scale mechanics. An extensive test program was undertaken to study the fatigue behavior of short fiber composites and validate the concept of the Master SN curve (MSNC) approach. The MSNC approach is compared with two prevalent approaches – strength based scaling and test based interpolation. The MSNC approach was found to be in a good agreement with the experimental results and was confirmed to be more accurate than the prevalent methods.     

Modeling the inelastic deformation and fracture of polymer composites – Part I: Plasticity model

A new transversely-isotropic elastic–plastic constitutive model for unidirectional fiber reinforced polymers (FRP) is presented. The model is able to represent the fully nonlinear mechanical behavior under multi-axial loading conditions and under triaxial stress states prior to the onset of cracking. Since associated flow rules often give a wrong prediction of plastic Poisson coefficients, a non-associated flow rule is introduced to provide realistic predictions of the volumetric plastic strains. This paper focusses on the simulation of triaxiality dependent plasticity based nonlinearities of FRP until failure occurs. The onset and propagation of failure is predicted by a new smeared crack model presented in an accompanying paper (Camanho et al., 2012). In order to demonstrate the capabilities of the new material model, a yield surface parameter identification for IM7-8552 carbon epoxy is presented and simulations of quasi-static transverse and off-axis compression tests and of uniaxial compression tests superimposed with various values of hydrostatic pressure are shown as a model verification.     

“Complete” system monitoring of polymer matrix composites

In situ, real time analysis of the chemical interactions occurring within the interphase of fiberglass fiber-reinforced polymer matrix composites (PMCs) has been accomplished through utilization of fiber optic sensors. The fiber size, as well as the composition of the thin cladding, closely approximates industrial fiberglass fibers, which allows the fibers to function simultaneously as model fiber-reinforcements and evanescent wave sensors. Using this sensor technology, the current research has shown that reactions occurring between the fiber surface, adsorbed silane coupling agent, and polymer can be monitored using FT-NIR spectroscopy. Two PMC systems have been chosen to demonstrate the ability to monitor complex interphase chemistry in situ and in real time.     

Fabrication and machining of ceramic composites — A review on current scenario

Ceramic matrix composites (CMCs) are the best-suited material for various engineering application due to their superior properties. The different processing methods involved in the fabrication and machining of these CMCs are a center for attraction to researchers and industrial society. This review article primarily focuses on the development of different processing methods and machining methods for ceramic matrix composites since the last few years. Out of these fabrication methods, powder metallurgy emerged as a most promising and cost-effective technique. In addition, electric discharge machining (EDM) has proved to be time saving, cost effective, and capable of machining complex shapes in composites. At the end, challenges in the processing and machining of ceramic matrix composites have been identified from the literature, and further benefits of microwave sintering and electric discharge machining of materials have been addressed in the paper.