J. Compos. Sci., Volume 6, Issue 1 (January 2022) – 31 articles

In industrial applications where contact behavior of materials is characterized, fretting-associated fatigue plays a vital role as a failure agitator. While considering connection, it encounters friction. Biomaterials like polytetrafluoroethylene (PTFE) and ultra-high-molecular-weight polyethylene (UHMWPE) are renowned for their low coefficient of friction and are utilized in sophisticated functions like the hip joint cup and other biomedical implants. In addition to the axial stresses, some degree of dynamic bending stress is also developed occasionally in those fretting contacts. This research investigated the fracture behavior of a polymer PTFE under bending fretting fatigue. Finite element analysis justified the experimental results. A mathematical model is proposed by developing an empirical equation for fracture characterization in polymers like PTFE. It was found that the bending stiffness exists below the loading point ratio (LPR) 3.0, near the collar section of the specimen. Along with fretting, the bending load forces the specimen to crack in a brittle-ductile mode near the sharp-edged collar where the maximum strain rate, as well as stress, builds up. For a loading point ratio of above 3, a fracture takes place near the fretting pads in a tensile-brittle mode. Strain proportionality factor, k was found as a life optimization parameter under conditional loading. The microscopic analysis revealed that the fracture striation initiates perpendicularly to the fretting load. The fretting fatigue damage characteristic of PTFE may have a new era for the biomedical application of polymer-based composite materials. Full article

The current review paper studies the most noteworthy points in the fabrication of inorganic, eco-benign geopolymer mortar stressing the valorisation of Waste of Glasses (WG) about its properties and applications. Only a few studies are so far accessible on the topic, and therefore, more advanced studies in this respect will be valuable to construction industries and the research scientist, too. Mostly, the centre of attention on its valorisation with WG points a finger to its attitude to embrace the “conversion of wastes into best” strategy. Up until now, their character is neither well understood nor as embraced as OPC mortars. That is why this article reviews its confined literature with an aim to comprehend the valorisation of WG incorporation with geopolymer mortar, and it also reviews studies on its properties and applications, establishing it as a forthcoming constructive, productive, cost-effective, and sustainable large-scale construction material. The recommendations of this paper will be helpful for potential researchers on the topic. However, there are some challenges, such as curing impediments, occasionally practical antagonises of use, a restrained chain of supply, and a precondition for a sharp-eyed command of mixing design for preparing it for use in roadways to replace OPC counterparts in industry. When fabricated by employing abundantly available precursors, activators, and WG up to the standard superior control of varied properties, chiefly strength, durability, and the low-carbon footprints of alkali activators, GP mortars supplemented with WG are ground-breaking approaches to part of the prospect toolbox of sustainable and reasonably inexpensive construction materials. Finally, the paper identifies research work challenges, endorsement of utilisation, and most essentially the features of its properties and pertinent discussions for this promising new kind of valorised construction material. Full article

To answer the question “How does lanthanide doping in iron oxide affect cure kinetics of epoxy-based nanocomposites?”, we synthesized samarium (Sm)-doped Fe₃O₄ nanoparticles electrochemically and characterized it using Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-Ray analysis (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy analyses (XPS). The magnetic particles were uniformly dispersed in epoxy resin to increase the curability of the epoxy/amine system. The effect of the lanthanide dopant on the curing reaction of epoxy with amine was explored by analyzing differential scanning calorimetry (DSC) experimental data based on a model-free methodology. It was found that Sm³⁺ in the structure of Fe₃O₄ crystal participates in cross-linking epoxy by catalyzing the reaction between epoxide rings and amine groups of curing agents. In addition, the etherification reaction of active OH groups on the surface of nanoparticles reacts with epoxy rings, which prolong the reaction time at the late stage of reaction where diffusion is the dominant mechanism. Full article

This paper deals with preparing a functional composite carbon fiber with a large surface area for spilled oil cleaning. The composite fiber consisted of photosensitive oxide particles and polymer-derived carbon. It was made by co-spinning the polymer and metallic compounds. After heat treatment at high temperatures, an activated carbon fiber containing oxide particles was obtained. The particles were found distributed in the fiber and at the surface of the fiber. The composite fiber was found sensitive to sunlight. Fiber mats made of the composite fiber possessed a high surface area for oil absorption and removal. Cobalt(II) titanate particles were obtained from the reaction of titanium dioxide and cobalt oxide. The reaction happened in situ through the hydrolysis of metallic compounds in the spun fiber. The titanium dioxide and cobalt(II) titanate particle-containing fibers demonstrated the photoactivity in the visible light spectrum. It was concluded that particle-containing composite carbon fiber mats can be prepared successfully by co-electrospinning. Due to the oleophilic property and the high active surface area, the composites are suitable for spilled oil cleaning through fast absorption. Full article

In thermoplastic composites, the polymeric matrix upon exposure to heat may melt, decompose and deform prior to burning, as opposed to the char-forming matrices of thermoset composites, which retain their shape until reaching a temperature at which decomposition and ignition occur. In this work, a theoretical and numerical heat transfer model to simulate temperature variations during the melting, decomposition and early stages of burning of commonly used thermoplastic matrices is proposed. The scenario includes exposing polymeric slabs to one-sided radiant heat in a cone calorimeter with heat fluxes ranging from 15 to 35 kW/m². A one-dimensional finite difference method based on the Stefan approach involving phase-changing and moving boundary conditions was developed by considering convective and radiative heat transfer at the exposed side of the polymer samples. The polymers chosen to experimentally validate the simulated results included polypropylene (PP), polyester (PET), and polyamide 6 (PA6). The predicted results match well with the experimental results. Full article

Dispersion of carbon nanotubes (CNT) in solvents and/or polymers is essential to reach the full potential of the CNTs in nanocomposite materials. Dispersion of CNTs is especially challenging due to the van-der-Waals attraction forces between the CNTs, which let them tend to re-bundle and/or re-aggregate. This paper presents a brief analysis of the quality and stability of functionalized multiwalled carbon nanotubes (fMWCNT) dispersion on polar solvents. A comparative study of functionalized CNT dispersion in water, methyl, and alcohol-based organic solvents has been carried out and the dispersion has been characterized by UV-VIS spectroscopy, electrochemical characterization such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Visual analysis of the dispersion has been investigated for up to 14 days to assess the dispersion’s stability. Based on the material characterization, it was observed that the degree of affinity fMWCNT with -COOH group highly depends on the polarity of the solvent, where the higher the polarity, the better the interaction of fMWCNT with solvents. Full article

The thermoelectric behavior of polypropylene (PP) based nanocomposites containing single walled carbon nanotubes (SWCNTs) and five kinds of ionic liquids (Ils) dependent on composite composition and electron beam irradiation (EB) was studied. Therefore, several samples were melt-mixed in a micro compounder, while five Ils with sufficiently different anions and/or cations were incorporated into the PP/SWCNT composites followed by an EB treatment for selected composites. Extensive investigations were carried out considering the electrical, thermal, mechanical, rheological, morphological and, most significantly, thermoelectric properties. It was found that it is possible to prepare n-type melt-mixed polymer composites from p-type commercial SWCNTs with relatively high Seebeck coefficients when adding four of the selected Ils. The highest Seebeck coefficients achieved in this study were +49.3 µV/K (PP/2 wt.% SWCNT) for p-type composites and −27.6 µV/K (PP/2 wt.% SWCNT/4 wt.% IL type AMIM Cl) for n-type composites. Generally, the type of IL is decisive whether p- or n-type thermoelectric behavior is achieved. After IL addition higher volume conductivity could be reached. Electron beam treatment of PP/SWCNT leads to increased values of the Seebeck coefficient, whereas the EB treated sample with IL (AMIM Cl) shows a less negative Seebeck coefficient value. Full article

Ultra high-temperature ceramic matrix composites (UHTCMCs) based on carbon fibre (Cf) have been shown to offer excellent temperature stability exceeding 2000 °C in highly corrosive environments, which are prime requirements for various aerospace applications. In C³Harme, a recent European Union-funded Horizon 2020 project, an experimental campaign has been carried out to assess and screen a range of UHTCMC materials for near-zero ablation rocket nozzle and thermal protection systems. Samples with ZrB₂-impregnated pyrolytic carbon matrices and 2.5D woven continuous carbon fibre preforms, produced by slurry impregnation and radio frequency aided chemical vapour infiltration (RF-CVI), were tested using the vertical free jet facility at DLR, Cologne using solid propellants. When compared to standard CVI, RFCVI accelerates pyrolytic carbon densification, resulting in a much shorter manufacturing time. The samples survived the initial thermal shock and subsequent surface temperatures of >2000 °C with a minimal ablation rate. Post-test characterisation revealed a correlation between surface temperature and an accelerated catalytic activity, which lead to an understanding of the crucial role of preserving the bulk of the sample. Full article

The development of cracks, owing to a relatively lower tensile strength of concrete, diverse loading, and environmental factors driving the deterioration of structures, is an inescapable key concern for engineers. Reparation and maintenance operations are thus extremely important to prevent cracks from spreading and mitigating the lifetime of structures. However, ease of access to the cracked zone may be challenging, and it also needs funds and manual power. Hence, autonomous sealing of cracks employing microorganisms into the concrete sans manual intervention is a promising solution to the dilemma of the sustainable improvement of concrete. ‘Ureolytic bacteria’, key organism species in rumen-producing ‘urease’ enzymes such as Bacillus pasteurii or subtilis—when induced—are capable of producing calcium carbonate precipitations into the concrete. As their cell wall is anionic, CaCO₃ accumulation on their surface is extensive, and the whole cell, therefore, becomes crystalline and ultimately plugs pores and cracks. This natural induction technique is an environmentally friendly method that researchers are studying intensively. This manuscript reviews the application process of bacterial healing to manufacture autonomous self-healing bacterial concrete. Additionally, it provides a brief review of diverse attributes of this novel concrete which demonstrate the variations with the auto-addition of different bacteria, along with an evaluation of crack healing as a result of the addition of these bacteria directly into concrete or after encapsulation in a protective shell. Comparative assessment techniques for autonomous, bio-based self-healing are also discussed, accompanied by progress, potential, modes of application of this technique, and its resultant benefits in the context of strength and durability. Imperatives for quantitative sustainability assessment and industrial adoption are identified, along with the sealing of artificially cracked cement mortar with sand as a filling material in given spaces, as well as urea and CaCl₂ medium treatment with Bacillus pasteurii and Sporosarcina bacteria. The assessment of the impact on the compressive strength and rigidity of cement mortar cubes after the addition of bacteria into the mix is also considered. Scanning electron microscope (SEM) images on the function of bacteria in mineral precipitation that is microbiologically induced are also reviewed. Lastly, future research scope and present gaps are recognised and discussed. Full article

The objective of this paper is to compare the thermal behavior of a light frame timber wall by measuring 15 test samples with various insulation materials versus a theoretical simulation with the use of a software. This work establishes the variance between the two different methods to measure the thermal transmittance coefficient of timber walls. It is verified that the mean percentage alteration between the two methods is 4.25%. Furthermore, this approach proved that with the use of a simulation software, additional readings (humidity, vapor flux, heat flux, and vapor pressure) can also be considered and measured, enhancing the overall development of a timber wall. This can provide additional information regarding to the characteristics of the masonry’s elements assisting in an improved design of a timber wall with upgraded performance. Full article

In tape placement process, the laying angle and laying sequence of laminates have proven their significant effects on the mechanical properties of carbon fibre reinforced composite material, specifically, laminates. In order to optimise these process parameters, an optimisation algorithm is developed based on the principles of genetic algorithms for improving the precision of traditional genetic algorithms and resolving the premature phenomenon in the optimisation process. Taking multi-layer symmetrically laid carbon fibre laminates as the research object, this algorithm adopts binary coding to conduct the optimisation of process parameters and mechanical analysis with the laying angle as the design variable and the strength ratio R as the response variable. A case study was conducted and its results were validated by the finite element analyses. The results show that the stresses before and after optimisation are 116.0 MPa and 100.9 MPa, respectively, with a decrease of strength ratio by 13.02%. The results comparison indicates that, in the iterative process, the search range is reduced by determining the code and location of important genes, thereby reducing the computational workload by 21.03% in terms of time consumed. Through multiple calculations, it validates that “gene mutation” is an indispensable part of the genetic algorithm in the iterative process. Full article

The chemical supercritical fluid infiltration process is a recent variation of the chemical vapor infiltration (CVI) process that allows rapid and efficient manufacturing of ceramic-matrix composites (CMCs), albeit still needing optimization. This article proposes a quantitative assessment of the process dynamics through experiments and modeling. The kinetics of carbon deposition were determined through two sets of experiments: CVD on a single filament at pressures between 10 and 50 bar and infiltration at pressures ranging between 50 and 120 bar. The CVI experiments were conducted under important thermal gradients and were interpreted using a model-based reconstitution of these gradients. We found that (i) the kinetic law has to incorporate the potential effect of the reverse reaction (i.e., etching of C by H${}_2$); (ii) the activation energy and pre-exponential factor both decrease with pressure up to 50 bar, then remain roughly constant, and (iii) although the apparent activation energy is modest, a favorable situation occurs in which an infiltration front builds up and travels from the hottest to the coldest part of the preform due to the presence of sufficient heat flux. A numerical simulation of the process, based on the solution of momentum, heat, and mass balance equations, fed with appropriate laws for the effective transfer properties of the porous medium and their evolution with infiltration progress, was performed and validated by comparing the simulated and actual infiltration profiles. Full article

Biophysical cues can regulate stem cell behaviours and have been considered as critical parameters of synthetic biomaterials for tissue engineering. In particular, hydrogels have been utilized as promising biomimetic and biocompatible materials to emulate the microenvironment. Therefore, well-defined mechanical properties of a hydrogel are important to direct desirable phenotypes of cells. Yet, limited research pays attention to engineering soft hydrogel with improved cell adhesive property, which is crucial for stem cell differentiation. Herein, we introduce silica nanoparticles (SiO₂ NPs) onto the surface of methacrylated hyaluronic (MeHA) hydrogel to manipulate the presentation of cell adhesive ligands (RGD) clusters, while remaining similar bulk mechanical properties (2.79 ± 0.31 kPa) to that of MeHA hydrogel (3.08 ± 0.68 kPa). RGD peptides are either randomly decorated in the MeHA hydrogel network or on the immobilized SiO₂ NPs (forming MeHA–SiO₂). Our results showed that human mesenchymal stem cells exhibited a ~1.3-fold increase in the percentage of initial cell attachment, a ~2-fold increase in cell spreading area, and enhanced expressions of early-stage osteogenic markers (RUNX2 and alkaline phosphatase) for cells undergoing osteogenic differentiation with the osteogenic medium on MeHA–SiO₂ hydrogel, compared to those cultured on MeHA hydrogel. Importantly, the cells cultivated on MeHA–SiO₂ expressed a ~5-fold increase in nuclear localization ratio of the yes-associated protein, which is known to be mechanosensory in stem cells, compared to the cells cultured on MeHA hydrogel, thereby promoting osteogenic differentiation of stem cells. These findings demonstrate the potential use of nanomaterials into a soft polymeric matrix for enhanced cell adhesion and provide valuable guidance for the rational design of biomaterials for implantation. Full article

Lack of cost information is a barrier to acceptance of 3D woven preforms as reinforcements for composite materials, compared with 2D preforms. A parametric, resource-based technical cost model (TCM) was developed for 3D woven preforms based on a novel relationship equating manufacturing time and 3D preform complexity. Manufacturing time, and therefore cost, was found to scale with complexity for seventeen bespoke manufactured 3D preforms. Two sub-models were derived for a Weavebird loom and a Jacquard loom. For each loom, there was a strong correlation between preform complexity and manufacturing time. For a large, highly complex preform, the Jacquard loom is more efficient, so preform cost will be much lower than for the Weavebird. Provided production is continuous, learning, either by human agency or an autonomous loom control algorithm, can reduce preform cost for one or both looms to a commercially acceptable level. The TCM cost model framework could incorporate appropriate learning curves with digital twin/multi-variate analysis so that cost per preform of bespoke 3D woven fabrics for customised products with low production rates may be predicted with greater accuracy. A more accurate model could highlight resources such as tooling, labour and material for targeted cost reduction. Full article

SiO₂-poly(2-hydroxyethyl methacrylate) (pHEMA)-based composites have been widely used as biomaterials owing to their biocompatibility. However, they have not yet been applied as tooth restorative materials because of their poor mechanical properties. In the present paper, we develop a novel SiO₂/pHEMA-based composite with a polymer-infiltrated network (PICN) structure for use in dental restorative materials. A mixture of SiO₂ nanoparticles and a poly(vinyl alcohol) binder was sintered at 950 °C to fabricate a porous SiO₂ block. A monomer mixture containing 70 wt%-HEMA/30 wt%-ethylene glycol dimethacrylate and a benzoyl peroxide initiator was infiltrated into the porous SiO₂ block and heat-polymerized to fabricate the SiO₂/pHEMA-based composite with a PICN structure. The composite was characterized according to its mechanical properties, surface free energy, and bonding properties with a dental adhesive. The flexural strength was 112.5 ± 18.7 MPa, the flexural modulus was 13.6 ± 3.4 GPa, and the Vickers hardness was 168.2 ± 16.1, which are similar values to human teeth. The surface free energy of the polar component of the composite was 19.6 ± 2.5 mN/m, suggesting that this composite has an active surface for bonding with the adhesive. The composite bonded well to the adhesive, in the presence of a silane coupling agent. The SiO₂/pHEMA-based composite was demonstrated to be a potential candidate for dental restorative materials. Full article

Contrary to other polymer processing methods, additive manufacturing processes do not require any pressure during the consolidation of layers. This study investigates the effect of high ambient pressure on the consolidation of layers during the FDM process and their analysis of mechanical properties. An experimental setup was arranged, consisting of a 3D printer integrated into a customized Autoclave, to achieve high strength properties for 3D printed parts as like injection-molded specimens. The autoclave can maintain 135 bar of pressure and a maximum temperature of 185 °C. 3D printing with PLA was carried out at 0 bar, 5 bar, and 10 bar. Tensile, flexural, and Charpy tests were conducted on printed specimens, and the effect of pressure and temperature on 3D-printed samples were analyzed. It could be shown that autoclave preheating before printing and autoclave pressure during printing improves the consolidation of layers immensely. The pressure inside the autoclave provokes a more intimate contact between the layer surfaces and results in higher mechanical properties such as yield strength, Young’s modulus, and impact strength. The properties could be raised 100%. Full article

This review discusses, in brief, the various synthetic methods of two widely-used nanofillers; phyllosilicate and graphene. Both are 2D fillers introduced into hydrogel matrices to achieve mechanical robustness and water uptake behavior. Both the fillers are inserted by physical and chemical gelation methods where most of the chemical gelation, i.e., covalent approaches, results in better physical properties compared to their physical gels. Physical gels occur due to supramolecular assembly, van der Waals interactions, electrostatic interactions, hydrophobic associations, and H-bonding. For chemical gelation, in situ radical triggered gelation mostly occurs. Full article

The mechanism of the crack propagation in three dimensional (3D) glass-fiber warp interlock epoxy composites under fatigue loading was investigated via time-lapse micro-computed tomography (µCT) observations. Two different composite samples were manufactured by means of a resin transfer molding (RTM) process under two different constant injection pressure conditions to generate intrayarn and interyarn voids separately. Fatigue loads were applied by blocks of 10⁵ cycles and followed by µCT measurements. Regions of interest for micro tomography scans were selected based on hot spots detected by infrared thermography. After the analysis of the obtained data, it was observed that detectable cracks were generally initiated by debonding in the zone between two adjacent warp yarns and grew along their interface. Then, these cracks propagated along one of the warp yarns aligned in the loading direction while remaining in the middle of the specimen cross-section. The coalescence of the cracks and further propagation to the weakest zones were observed around and after the middle lifetime. Finally, we demonstrated the influence of the void defects at different material scales. I was found that interyarn voids have relatively little influence on the fatigue performance whereas they can, sometimes, attract and deviate cracks in the matrix zone between adjacent yarns. It was also shown that the intrayarn voids are crucial to degenerate the fatigue performance of the yarns at the micro-scale. Full article

Hybridization of carbon fiber composites can increase the material damping of composite parts. However, there is little research on a direct comparison of different fiber materials—particularly for carbon fiber intraply-hybrid composites. Hence, the mechanical- and damping properties of different carbon fiber intraply hybrids are analyzed in this paper. Quasi unidirectional fabrics made of carbon, aramid, Vectran and cellulose fibers are produced, and their mechanical properties are analyzed. The material tests show an increased material damping due to the use of Vectran and aramid fibers, with a simultaneous reduction in strength and stiffness. Full article

Lithium batteries utilizing solid-state electrolytes have the potential to alleviate their safety hazard, reduce packaging volume, and enable flexible design. Polymer/ceramic composite electrolytes (CPE) are more attractive because the combination is capable of remedying and/or transcending individual constituent’ properties. Recently, we fabricated a series of free-standing composite electrolyte membranes consisting of Li_1.4Al_0.4Ge_1.6(PO₄)₃ (LAGP), polyethylene oxide (PEO), and lithium salts. In this study, we characterized thermal and mechanical properties of the CPEs with two representative lithium salts, i.e., lithium boron fluoride (LiBF₄) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). We found that the type of lithium salt can prevail the LAGP ceramic loadings on altering the key properties. It is observed that LiTFSI, compared with LiBF₄, causes more significant reduction in terms of the crystallinity of PEO, melting transition, and mechanical strengths. The differences in these aspects can be ascribed to the interactions between the polymer matrix and anions in lithium salt. Full article

Water polluted by organic dyes is a serious environmental problem. In response to this, the aim of this research is to degrade dye wastewater using a modified photocatalyst. Since sunlight only has less than 5% UV energy, for a general photocatalyst, using sunlight for excitation to decompose organic pollutants is not an effective way. Therefore, we manufactured the modified photocatalyst by zirconium dioxide, graphene oxide, and titanium dioxide. This was to better improve the photo-degradation efficiency for the degradation of organic pollutants. The modified photocatalyst was analyzed by X-ray diffractometer (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), Scanning Electron Microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDS). The results demonstrated that the modified photocatalyst can be activated by the absorption of visible light. Additionally, the band gap of the modified photocatalyst would decrease. The photodegradation percentage of the modified photocatalyst under visible light (Philips TL-D 8W/865 fluorescent tube) for 4 h reached up to 49.92%. At the third test after ultrasonic washing for the cyclic test, the photodegradation percentage of the modified photocatalyst could still maintain at 47.71%. This indicates that the modified photocatalyst has good stability and reusability, and so this can be reused in this regard. Full article

Robust finite element models are utilised for their ability to predict simple to complex mechanical behaviour under certain conditions at a very low cost compared to experimental studies, as this reduces the need for physical prototypes while allowing for the optimisation of components. In this paper, various parameters in finite element techniques were reviewed to simulate the crushing behaviour of glass/epoxy tubes with different material models, mesh sizes, failure trigger mechanisms, element formulation, contact definitions, single and various numbers of shells and delamination modelling. Six different modelling approaches, namely, a single-layer approach and a multi-layer approach, were employed with 2, 3, 4, 6, and 12 shells. In experimental studies, 12 plies were used to fabricate a 3 mm wall thickness GFRP specimen, and the numerical results were compared with experimental data. This was achieved by carefully calibrating the values of certain parameters used in defining the above parameters to predict the behaviour and energy absorption response of the finite element model against initial failure peak load (stiffness) and the mean crushing force. In each case, the results were compared with each other, including experimental and computational costs. The decision was made from an engineering point of view, which means compromising accuracy for computational efficiency. The aim is to develop an FEM that can predict energy absorption capability with a higher level of accuracy, around 5% error, than the experimental studies. Full article

A model that predicts the stiffness degradation in multidirectional reinforced laminates due to off-axis matrix cracks is proposed and evaluated using data from fatigue experiments. Off-axis cracks are detected in images from the fatigue tests with automated crack detection to compute the crack density of the off-axis cracks which is used as the damage parameter for the degradation model. The purpose of this study is to test the effect of off-axis cracks on laminate stiffness for different laminate configurations. The hypothesis is that off-axis cracks have the same effect on the stiffness of a ply regardless of the acting stress components as long as the transverse stress is positive. This hypothesis proves to be wrong. The model is able to predict the stiffness degradation well for laminates with a ply orientation similar to the one used for calibration but deviates for plies with different in-plane shear stress. This behavior can be explained by the theory that off-axis cracks develop by two different micro damage modes depending on the level of in-plane shear stress. It is found that besides influencing the initiation and growth of off-axis cracks, the stiffness degradation is also mode dependent. Full article

Anti-rodent polymer composites were prepared using non-toxic substances denatonium benzoate (DB) and capsicum oleroresin (CO) mixed with polyvinyl chloride (PVC) matrix. DB is mixed in zinc stearate (ZnSt) called DB/ZnSt, and CO, providing burning sensation, is impregnated in mesoporous silica named SiCO. There are three sets of sample: Blank, composites Set I and Set II. Set I consists of DB/ZnSt at concentration of 1.96 wt% and SiCO at concentration of 12.16 wt%, 14.47 wt%, 18.75 wt% and 23.53 wt%. Set II comprises SiCO at the same amount of Set I. The anti-rodent composites studied are anti-gnawing, surface morphology, thermo-mechanical and rheological properties. Anti-rodent testing is analyzed by one-way blocked analysis of variance (ANOVA) and compared with Tukey test with a 95% level of significance, presenting good anti-gnawing efficiency. The best rat-proof sample is II.4, consisting of SiCO 23.53 wt%, which presents percentage of weight loss from gnawing at 1.68% compared to weight loss of neat PVC at 59.74%. The addition of SiCO at concentration ranging from 12.16 to 23.53 wt% reduces tensile strength around 25–50%, elongation at break strength around 2–23%, shear storage modulus (G′) around 30%, shear loss modulus (G″) shear viscosity (η) and glass transition (T_g) around 43% compared to Blank. The increase in SiCO concentration slightly improves the thermal stability of PVC composites around 3%, but the addition of DB/ZnSt at 1.96 wt% slightly reduces those properties. Full article

Additive manufacturing technologies, well known as three-dimensional printing (3DP) technologies, have been applied in many industrial fields, including aerospace, automobiles, shipbuilding, civil engineering and nuclear power. However, despite the high material utilization and the ability to rapidly construct complex shaped structures of 3D printing technologies, the application of additive manufacturing technologies in railway track infrastructure is still at the exploratory stage. This paper reviews the state-of-the-art research of additive manufacturing technologies related the railway track infrastructure and discusses the challenges and prospects of 3D printing technology in this area. The insights will not only help the development of 3D printing technologies into railway engineering but also enable smarter railway track component design and improve track performance and inspection strategies. Full article

The creation of an ideal surfboard is art. The design and construction depend on the individual surfer’s skill level and type of the required performance. In this research, four fuselage concepts were carefully explored to meet the following unique needs: lightweight, strong, and a fast-manufacturing process. The fuselages were manufactured by compression moulding using skin and core materials. The skin material was selected to be unidirectional (UD) carbon fibre, discontinuous carbon fibre (SMC) and Filava quadriaxial fibre impregnated with epoxy, while the core material was selected to be lightweight PVC foam. To assess the mechanical performance, three-point bending has been performed according to BS-ISO 14125 and validated using Finite Element Analysis (FEA) using Ansys software. As expected, the flexural test revealed that the UD carbon fibre fuselage was the strongest and SMC was the weakest, while large deflection was seen in Filava fibre fuselages before failure, showing great reactive flex that promotes projection during surfing. The experimental results show good agreement with FEA simulation, and the locations of the physical failure in the fuselage matches the location of maximum flexural stress obtained from FEA simulation. Although all fuselages were found to carry a surfer weight of 150 kg, including a factor of safety 3, except the SMC fuselage, due to shrinkage. The Filava fibre fuselages were seen to have a large deflection before failure, showing great flexibility to handle high ocean waves. This promotes the potential use of reactive flex in high performance sports equipment, such as surfing boards. A large shrinkage must be taken under consideration during compression moulding that depends on fibre orientation, resin nature, and part geometry. Full article

This paper aims to investigate the ability of an eco-friendly and cheap treatment based on sodium acetate solutions to improve the mechanical properties of flax fiber-reinforced composites. Flax fibers were treated for 5 days (i.e., 120 h) at 25 °C with mildly alkaline solutions at 5%, 10% and 20% weight content of the sodium salt. Quasi-static tensile and flexural tests, Charpy impact tests and dynamical mechanical thermal (DMTA) tests were carried out to evaluate the mechanical properties of the resulting composites. Fourier transform infrared analysis (FTIR) was used to evaluate the chemical modification on the fibers surface due to the proposed treatment, whereas scanning electron microscope (SEM) and helium pycnometry were used to get useful information about the morphology of composites. It was found that the treatment with 5% solution of sodium acetate leads to the best mechanical performance and morphology of flax fiber-reinforced composites. SEM analysis confirmed these findings highlighting that composites reinforced with flax fibers treated in 5% sodium acetate solution show an improved morphology compared to the untreated ones. On the contrary, detrimental effects on the morphology as well as on the mechanical performance of composites were achieved by increasing the salt concentration of the treating solution. Full article

In the present work, N-TiO_2−x/Pt was synthesized using a homemade nitrogen plasma (AC) discharge system. The overall procedure use of low-power nitrogen plasma (100 watts) with 1 and 2 h of plasma discharge to successfully impregnate platinum nanoparticles on P25 titanium dioxide. The obtained samples were characterized using X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The results reveal the incorporation of metallic Pt up to 2.9% on the surface of TiO₂ by increasing the duration of plasma discharge by up to two hours with a constant power of 100 watts. Likewise, the incorporation of nitrogen atoms into a lattice crystal was also favored, confirming a direct relationship between the amount of Pt and nitrogen atoms introduced in TiO₂ as a function of the duration of plasma treatment. By characterizing nanoparticles loaded on a N-TiO_2−x/Pt surface, we show that joined platinum nanoparticles have two different patterns, and the boundary between these two regions coalesces. The results demonstrate that the use of nitrogen plasma to impregnate platinum nanoparticles on the surface of TiO₂ to obtain N-TiO_2−x/Pt allows wide and relevant physics and chemistry applications. Full article

Earth bricks are a traditional eco-friendly construction material. In this study, harbor-dredged sediments were used along with hemp shiv to develop a brick manufacturing procedure and compaction techniques to produce durable earth bricks for the valorization of waste hemp shiv and dredged sediments. Prismatic specimens of size 4 × 4 × 16 cm³ were manufactured with Dunkirk sediments after analyzing their suitability for earth bricks according to the French standard for flexural strength test to observe the indirect tensile strength and impact of the compaction techniques on the strength of bricks. Crude bricks were manufactured with varying hemp shiv content from 0% to 5% by mass. Compaction techniques such as dynamic compaction, static compaction, and tamping were applied. The effect of hemp shiv content and compaction techniques was evaluated with a flexural strength test and the distribution of fibers in bricks. Grain size analysis of sediments with French and Spanish standards shows that the sediments granulometry is suitable for earth bricks. The flexural strength testing of bricks indicates that bricks with saturated hemp shiv have higher flexural strength. Earth bricks have maximum strength with dynamic compaction with 1% hemp shiv, which satisfies the adobe bricks tensile strength requirements that vary from 0.012 to 0.025 MPa (NZS 4298, 1998; NORMA E.080 (2017). Full article

Continuous inspection of critical zones is essential to monitor the state of strain within offshore wind blades, thus, enabling appropriate actions to be taken when needed to avoid heavy maintenance. Wind-turbine blades contain various substructures made of composites, sandwich panel, and bond-joined parts that need reliable Structural Health Monitoring (SHM) techniques. Embedded, distributed Fiber-Optic Sensors (FOS) are one of the most promising techniques that are commonly used for large-scale smart composite structures. They are chosen as monitoring systems for their small size, being noise-free, and low electrical risk characteristics. In recent works, we have shown that embedded FOSs can be positioned linearly and/or in whatever position with the scope of providing pieces of information about actual strain in specific locations. However, linear positioning of distributed FOS fails to provide all strain parameters, whereas sinusoidal sensor positioning has been shown to overcome this issue. This method can provide multiparameter strains over the whole area when the sensor is embedded. Nevertheless, and beyond what a sensor can offer as valuable information, the fact remains that it is a “flaw” from the perspective of mechanics and materials. In this article and through some mechanical tests on smart composites, evidence was given that the presence of embedded FOS influences the mechanical behavior of smart composites, whether for quasi-static or fatigue tests, under 3-point bending. Some issues directly related to the fiber-architecture have to be solved. Full article