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Purpose Process parameters in Fused Filament Fabrication (FFF) can affect mechanical and surface properties of printed parts. Numerous studies have reported parametric studies of various materials using full factorial and Taguchi design of experiments (DoEs). However, a comparison between the two are not well-established in literature. The purpose of this study is to compare full factorial and Taguchi DoEs to determine the effects of FFF process parameters on mechanical and surface properties of Nylon 6/66 copolymer. In addition, perform in-depth failure mechanism analysis to understand why the process parameters affect the responses. Design/methodology/approach A full factorial DoE was used to determine the effects of FFF process parameters, such as infill density, infill pattern, layer height and raster angle on responses, such as compressive strength, impact strength, surface roughness and manufacturing time of Nylon 6/66. Micro-computed tomography was used to analyse the impact test samples before and after impact and scanning electron microscope was used to understand the failure mechanism of infill and top layers. Differential scanning calorimetry (DSC) scans of infill and top layers were then taken to determine if a variation in crystallinity existed in different regions of the build. Findings Analysis of variance and main effects plots reveal that infill density has the greatest effect on mechanical and surface properties while manufacturing time is most affected by layer height for the polymer used. A 20% reduction in infill increased impact strength by 19% on average, X-ray images of some of the samples before and after impact tests are presented to understand the reason behind the difference. Moreover, DSC revealed a difference in the degree of crystallinity between the infill and top layers for 80% infill density samples. In addition, Taguchi DoE is realized to be a more efficient technique to determine optimum process parameters for responses that vary linearly as it reduces experimental effort significantly while providing mostly accurate results. Originality/value To the author’s knowledge, no published paper has reported a comparison between predictive DoE method with full factorial DoE to verify their accuracy in determining the effects of FFF process parameters on properties of printed parts. Also, a theory was developed based on DSC results that as the infill is printed faster, it cools slowly compared to the top layers, and hence the infill is in a less crystalline state when compared to the top layers. This increased the ductility of the infill (of 80% infill samples) and thus improved impact absorption.

Cases of verbal bullying are still prevalent among students in schools. Therefore, efforts are needed through various approaches to overcome the problem. One of the efforts that can be done is through the habituation of krama language in the school environment. This article aims to analyze the application of krama language as an educational communication ethic in Junior High School Islam Prestasi Al Mubtadi-ien Bantul in the perspective of Islamic education. The important issue discussed is the purpose and form of application of manners language as educational communication and its impact on the formation of student behavior seen from the perspective of Islamic education. This research is qualitative research using a phenomenological approach in Junior High School Islam Prestasi Al Mubtadi-ien Bantul, Yogyakarta. Data collection using observation, interviews, and documentation. Data analysis uses data reduction, data exposure, and inference/verification measures. Data collection using observation, interviews, and documentation. Data analysis uses data reduction, data exposure, and inference/verification measures. The results of this study showed: First, the form of educational communication ethics applied in Junior High School Islam Prestasi Al Mubtadi-ien Bantul is based on the cultural values of krama language carried out during the implementation of the learning process in the classroom and in interactions outside the classroom in the school environment. The application of krama language aims to shape student behavior and participate in preserving the culture of krama language as is done in a pesantren environment. Second, the application of communication ethics using Javanese culture krama in Junior High School Islam Prestasi Al Mubtadi-ien Bantul is considered to have provided positive benefits and impacts for students. Third, from the perspective of Islamic education, the application of krama language culture in Junior High School Islam Prestasi Al Mubtadi-ien Bantul is very relevant. Islam is very concerned about the ethical issue of communication. Islam teaches the delivery of information messages to citizens using good language, friendly and polite.

This study reports for the first time the use of water soluble sulfonated octa-phenyl POSS nanowhiskers for the surface treatment for carbon fibres using simple dip-coating method. The water soluble nature of the functionalized POSS makes it appealing from a formulation perspective as it can be applied simply using an aqueous media. The synthesis of the water soluble SOP-POSS was achieved via one-step aromatic electrophilic sulfonation of octaphenyl POSS. Collective results from NMR, XPS and FTIR analysis confirmed the meta mono-substitution of all phenyl rings in the starting material with a sulfonic group, leading to its water solubility. Surface treatment of commercially oxidized and unsized carbon fibres was achieved via simple dip-coating of the fibres in an aqueous media solution containing the synthesized SOP-POSS product. After the dip-coating process, the carbon fibres are homogeneously covered with surface adsorbed SOP-POSS nanowhiskers. Physico-chemical characterization of the fibres investigated by Inverse Gas Chromatography (IGC) revealed an improvement in surface chemical homogeneity associated with a significant increase in surface oxygen contents and an overall level of surface polarity comparable to commercially sized fibres. The interfacial adhesion properties between the treated carbon fibres and an epoxy matrix were investigated by single fibre fragmentation technique. The results of the tests revealed that significant enhancement of interfacial properties was achieved as a result of a combination of physical inter-molecular interactions at the fibre-matrix interface and localized nano-mechanical strengthening of the epoxy. The outcomes of this research lay the path forward for a potential simple surface treatment of commercial carbon fibres for Interfacial property improvement in composites.

Conventional two dimensional and low-definition measurement techniques for dosimetric verification of radiotherapy treatment deliveries are no longer adequate in the era of hypofractionation and extremely high dose gradients. New quality assurance (QA) tools with 3D capability and high definition are urgently needed. The purpose of this study was to evaluate the performance of one of the first such commercial systems as applied to CyberKnife (CK) radiotherapy/radiosurgery system. This study employed the recently developed commercial 3D patient-specific quality assurance (PSQA) system. Tissue-equivalent radiochromic polymer gel dosimeters, sealed in light protective thin-wall glass spheres (CrystalBalls), were mounted in a high-precision acrylic QA stand. Patient treatment plans were superimposed on the simulator CT scan of one selected CrystalBall and were irradiated in CK machine. CrystalBalls were then scanned using a laser CT scanner (OCTOPUS, MGS Research, Inc., DBA 3D Dosimetry, Madison, CT, USA). The simulator CT scan and the laser CT scan of the CrystalBall were registered in 6D using the VOLQA (MGS Research, Inc., DBA 3D Dosimetry, Madison, CT, USA) software. Planned and delivered dose distributions were compared by means of 3D gamma passing rates at user-selected acceptance criteria. Cumulative 3D dose-volume histograms and overlays of orthogonal profiles and isodoses both in 2D and in 3D were also generated, along with voxel statistics for dose difference and distance-to-agreement criteria. Twelve stereotactic radiosurgery/stereotactic radiotherapy/stereotactic body radiation therapy patients were selected randomly such that each set of two represented one of the six diagnoses: brain metastasis, trigeminal neuralgia, spine metastasis, prostate cancer, lung cancer and liver cancer. The validation of the 3D system was carried out by comparing the 2D gamma passing rates for all the patients using EBT3 films sandwiched between PMMA slabs and then analyzed with PTW VeriSoft software. The 3D gamma passing rate averaged over all patients studied was (90.5 ± 6.7) % at acceptance criteria of 2% (local) dose difference and 2 mm distance-to-agreement down to 20% isodose. For 3% (local) dose difference and 3 mm distance-to-agreement (also down to 20% cutoff dose), the average passing rate was (96.0 ± 3.1) %. The results of the study presented here form part of the information needed to assess suitability of a system and hence, the results suggest that the new high-definition 3D CrystalBall system can be a useful PSQA tool as a part of quality assurance for CK.

New anoxic and normoxic polymer gel dosimeters containing different concentrations of N-(3-Methoxypropyl) acrylamide (NMPA) are introduced in this investigation for radiotherapy treatment planning dose validation. NMPA dosimeters were irradiated to 20 Gy using the 10 MV photon beam of a medical linear accelerator under a constant dose rate. The polymerization of NMPA dosimeters occurs and increases monotonically with increasing absorbed dose. Nuclear magnetic resonance (NMR) was used to investigate the degree of polymerization of gels. The dose response in terms of spin–spin relaxation rate (R2) of NMPA dosimeters increased with the addition of glycerol. The influence of the x-ray radiation energy, dose, and dose rate, as well as the stability of the irradiated NMPA gel dosimeters were studied in order to show this preliminary study is indicative of a promising low-toxicity polymer gel dosimeter.

In recent years, there have been significant advances on materials development for additive manufacturing (AM) applications. However, the use of composites or nanocomposite materials for improved performance and multifunctionality are still limited. This review paper attempts to provide a comprehensive review of both commercially available materials as well as research activities related to recent progress on high-performance polymer nanocomposites that are being used in various AM techniques. Four AM techniques including Fused Filament Fabrication (FFF), Selective Laser Sintering (SLS), Multi Jet Fusion (MJF), and Stereolithography (SLA) are discussed. The development of printable polymer composites especially polymer nanocomposites is rapidly expanding the AM materials portfolio, which makes the production of multifunctional parts with complex structures possible.

Silk particles of different sizes and shapes were produced by milling and interactions with a series of polar and non-polar gaseous probes were investigated using an inverse gas chromatography technique. The surface energy of all silk materials is mostly determined by long range dispersive interactions such as van der Waals forces. The surface energy increases and surface energy heterogeneity widens after milling. All samples have amphoteric surfaces and the concentration of acidic groups increases after milling while the surfaces remain predominantly basic. We also examined powder compression and flow behaviours using a rheometer. Increase in surface energy, surface area, and static charges in sub-micron air jet milled particles contributed to their aggregation and therefore improved flowability. However they collapse under large pressures and form highly cohesive powder. Alkaline hydrolysis resulted in more crystalline fibres which on milling produced particles with higher density, lower surface energy and improved flowability. The compressibility, bulk density and cohesion of the powders depend on the surface energy as well as on particle size, surface area, aggregation state and the testing conditions, notably the consolidated and unconsolidated states. The study has helped in understanding how surface energy and flowability of particles can be changed via different fabrication approaches.

Silkworm cocoons are biological composite structures protecting the silkworms against environmental damage and physical attack by natural predators. In particular, some outdoor reared silk cocoons exhibit outstanding mechanical properties that are relevant to the higher level protection required to enhance the survival chance of silkworms while supporting their metabolic activity. The performance of composite materials strongly depends on the adhesion between the fiber reinforcement and matrix, with the surface properties of the fibers playing a key role in determining the level of adhesion achieved. For this reason it is important to study the surface properties of silk fibroin to further understand the composite properties of the cocoons. In this work, both the mechanical properties of the silk cocoons and silk fibroin were studied. The surface topography was examined using scanning probe microscopy (SPM), which revealed distinct longitudinal ridges and striations along the fiber axis of the four silk fiber types. The fibers were found to exhibit heterogeneity in surface energy as evidenced from inverse gas chromatography (IGC) measurements. The combination of excellent mechanical properties and the more energetically heterogeneous surface nature of the wild A. pernyi silk fibroin fibers correlates well with the excellent mechanical properties of the A. pernyi cocoons.

The performance of composite laminates depends on the adhesion between the fibre reinforcement and matrix, with the surface properties of the fibres playing a key role in determining the level of adhesion achieved. For this reason it is important to develop an in-depth understanding of the surface functionalities on the reinforcement fibres. In this work, multi-scale surface analysis of carbon fibre during the three stages of manufacture; carbonisation, electrolytic oxidation, and epoxy sizing was carried out. The surface topography was examined using scanning electron microscopy (SEM), which revealed longitudinal ridges and striations along the fibre-axis for all fibre types. A small difference in surface roughness was observed by scanning probe microscopy (SPM), while the coefficient of friction measured by an automated single fibre tester showed 51% and 98% increase for the oxidised and sized fibres, respectively. The fibres were found to exhibit heterogeneity in surface energy as evidenced from SPM force measurements. The unsized fibres were much more energetically heterogeneous than the sized fibre. A good correlation was found between fibre properties (both physical and chemical) and interlaminar shear strength (ILSS) of composites made from all three fibre types.

A range of polyacrylonitrile (PAN) and pitch based carbon fibre types (high, standard and intermediate modulus fibres) have been characterised using both physical and chemical techniques, the results highlighting the heterogeneity of the fibre. Nano-indentation showed variation in stiffness between different fibres of the same type as well as variation along a 20 μm length of a single fibre. Tensile tests showed variance of approximately 25% in tenacity for three different carbon fibre types but less variability in modulus with values from 8% to 19%. Raman spectroscopy showed variation in the graphitic content both between fibres of different origin as well as variation, with 0.5 μm spatial resolution, along the length of a single fibre. Inverse gas chromatography surface energy measurements of larger samples of fibres were carried out using the novel approach of incremental surface coverage by varying the probe molecule concentration and revealed different levels of energetic heterogeneity for PAN based fibres collected at different stages of carbon fibre production. The heterogeneity of the unoxidised fibres (collected after carbonisation) was restricted to about 15% of the fibre surface whereas the surface oxidised fibre sample (collected after the electrolytic oxidation bath) was heterogeneous over more than 30% and the sized fibres were shown to be quite homogeneous.

The surface of both oxidized and unoxidized unsized carbon fiber was functionalized using an aziridine linking group derived from reactive nitrenes. The aziridine functionality arose from the cyclization of a reactive nitrene species onto the highly electron rich graphitic surface of the carbon fibers; the nitrene species evolved from thermal N2 elimination from the corresponding (room temperature stable) azide. Surface functionalization using the nitrene approach was supported by X-ray Photoelectron Spectroscopy, in both oxidized and unoxidized carbon fiber. Attempts were also made to functionalize using amide chemistry, the two-step acid chloride coupling being successful for oxidized fibers by utilizing the carboxylic acid rich defect sites on the carbon fiber. None of the chemical treatment pathways had a significant impact on the tensile strength of the individual fibers, and atomic force microscopy revealed that fibers undergoing these treatment methodologies remained intact, without creating additional surface defects.

Combining continuous wave and pulsed plasma modes enables strong interfacial bonding of high levels of desired surface functional groups. The method has been applied to a thin film of multiwalled carbon nanotubes, a nanostructured and relatively inert material, using N2 + H2 plasma. A high density of primary amine groups (~2.6%) was achieved without damaging the tube surface. Contact angle measurements, using different probe liquids, plus model calculations of surface energy agree well with the spectroscopy and electron microscope results, i.e., the polar part shows significant changes while the non-polar part was unchanged. These results indicate that the wettability changes in the thin film of carbon nanotubes by the plasma treatment are due to the changes in surface chemistry. This confirms the effectiveness and practicality of the improved plasma method that should greatly help the use of nanotubes in applications from biomaterials to nanocomposites.

This work demonstrates that the interfacial properties in a natural fiber reinforced polylactide bio-composite can be tailored through surface adsorption of amphiphilic and biodegradable poly (ethylene glycol)-b-poly(l-lactide) (PEG-PLLA) block copolymers. The deposition from solvent solution of PEG-PLLA copolymers onto the fibrous substrate induced distinct mechanisms of molecular organization at the cellulosic interface, which are correlated to the hydrophobic/hydrophilic ratios and the type of solvent used. The findings of the study evidenced that the performance of the corresponding biocomposites with polylactide were effectively enhanced by using these copolymers as interfacial coupling agents. During the fabrication stage, diffusion of the polylactide in the melt induced a change in the environment surrounding block copolymers which became hydrophobic. It is proposed that molecular reorganization of the block copolymers at the interface occurred, which favored the interactions with both the hydrophilic fibers and hydrophobic polylactide matrix. The strong interactions such as intra- and intermolecular hydrogen bonds formed across the fiber-matrix interface can be accounted for the enhancement in properties displayed by the biocomposites. Although the results reported here are confined, this concept is unique as it shows that by tuning the amphiphilicity and the type of building blocks, it is possible to control the surface properties of the substrate by self-assembly and disassembly of the amphiphiles for functional materials.

In this work, an atmospheric pressure glow discharge helium plasma treatment was employed to modify the surface properties of jute fibres. The resulting bio-composites showed an increase in flexural properties and interlaminar shear strength (ILSS) compared to composites produced using untreated jute fibres. To understand the reason behind the ILSS improvement, the acid–base properties of jute fibres were determined by contact angle analysis using the capillary rise method. The results were fitted further to van Oss–Chaudhury–Good (vOCG) and Chang–Qin–Chen (CQC) models to determine the Lifshitz–van der Waals (LW) and acid–base components of surface energy. Surface energy determined by the vOCG model revealed that plasma treatment of jute fibre resulted in a 22% increase in total surface energy, a 19% increase in the LW component and a 24% increase in the acid–base component of surface energy. The increase in the acid–base component is due to the significant increase (69%) in the electron-accepting (γ + S)...

This work has focused on measuring the adhesion forces on both untreated and atmospheric helium plasma treated single jute fibre surfaces using scanning probe microscopy (SPM). The measurements were conducted on three differently aged surfaces for one week, three weeks and six weeks using a standard silicon nitride tip in force-volume (f-v) mode. Up to 256 adhesion data points were collected from various locations on the surface of the studied fibres using in-house developed software and the resulting data were statistically analysed by the histogram method. Results obtained from this analysis method were found to be very consistent with a small statistical variation. The work of adhesion, W a, was calculated from measured adhesion force using the Johnson–Kendall–Roberts (JKR) and Derjaguin–Muller–Toporov (DMT) models. Increases in both adhesion force and work of adhesion were observed on jute fibre with certain levels of atmospheric plasma treatment and ageing time.

Jute fabric was treated for various periods of time under atmospheric plasma glow discharge (APGD) using helium (He), helium/nitrogen (He/N), and helium/acetylene (He/Ac) gases. It was found that, for all gases studied, 10 s of treatment was enough to significantly improve the wetting behaviour of the fabric. Different levels of improvement of up to 55%, 62%, and 40% in flexural strength, flexural modulus, and interlaminar shear stress respectively were observed in composites produced from plasma treated fabrics. The storage modulus and glass transition temperature were also improved by up to 200% and 16 °C, respectively. Efforts were made in order to correlate the changes in surface roughness, tip-surface adhesion, and surface chemistry of the fibres (measured by XPS and FTIR) with the performance of the composites. In light of some of the trends, it has been postulated that low-molecular weight oxidised species have formed on the fibre surface during plasma and that the chemical nature of these species must have changed considerably depending on the type of gas mixture used, inducing various synergistic or antagonistic effects.

This study evaluated the performance of jute reinforced polyester bio-composites cured with an out-of-autoclave curing process, Quickstep™. The mode I fracture toughness (GIc), flexural, and thermo-mechanical properties of the composites were measured for cure cycle times of 5, 30, 60 and 90 min at an optimum cure temperature of 95 °C, and were compared to a reference composite laminate cured at room temperature. Generally, the Quickstep process was found to improve the degree of cure by up to 55% and the resistance to crack propagation of the resulting composites was found to be more stable. A balance in properties was obtained after 30 min of cure where an improvement in thermo-mechanical and fracture properties was observed, but on the other hand, was accompanied by a decrease in flexural strength and modulus compared to the reference sample. Shorter (i.e. 5 min) and longer cure cycle times (above 30 min) used by the Quickstep were found to be detrimental to the properties of the resulting composites.

This work investigates the mechanisms involved in the improvement of flexural properties of a jute/polyester composite when the reinforcement material has been atmospherically plasma treated using helium gas. All composites were laid-up by hand and cured using a Quickstep™ cure cycle. Surface characterization techniques including scanning probe microscopy (SPM), and surface wettability combined with fabric tensile strength, composite flexural strength and composite Mode-I properties have been used to quantify the effects of plasma modification. Flexural strength and modulus increased with plasma treatment time, reaching a maximum at 25 passes before decreasing. SPM topographical analysis showed that roughness of the fibre decreased as the plasma treatment time increased until 25 passes after which the roughness was found to increase again. The coefficient of friction increased rapidly after only a short plasma treatment time (5 passes) whilst wettability continued to increase until 25 passes after which i...

The dispersion state of individual MWCNT in the polymer matrix influences the mechanical, thermal, and electrical properties of the resulting composite. One method of obtaining a good dispersion state of MWCNT in a polymer matrix is to functionalize the surface of MWCNT using various treatments to enhance the surface energy and increase the dispersibility of MWCNT. In this study, wettability and surface energy of UV/O3and acid-treated multiwall carbon nanotubes (MWCNTs) and its polymethyl methacrylate (PMMA) polymer nanocomposites were measured using contact angle analysis in various solvent media. Contact angle analysis was based on ethylene glycol-water-glycerol probe liquid set and data was further fitted into geometric mean (Fowkes), van Oss-Chaudhury-Good (GvOC), and Chang-Qing-Chen (CQC) models to determine both nonpolar and acid base surface energy components. Analysis was conducted on MWCNT thin films subjected to different levels of UV/O3and acid treatments as well as their resulting MWCNT/PMMA nanocomposites. Contact angle analysis of thin films and nanocomposites revealed that the total surface energy of all samples was well fitted with each other. In addition, CQC model was able to determine the surface nature and polarity of MWCNT and its nanocomposites. Results indicated that the wettability changes in the thin film and its nanocomposites are due to the change in surface chemistry. Finally, electrical properties of nanocomposites were measured to investigate the effect of surface functionality (acid or basic) on the MWCNT surfaces.

The homogeneous and stable dispersion of carbon nanotubes (CNTs) in solvents is often a prerequisite for their use in advanced materials. Dispersion procedures, reagent concentration as well as the interactions among reagent, defective CNTs and near-perfect CNTs will affect the resulting CNT dispersion properties. This study, for the first time, presents a detailed comparison between two different approaches for dispersing CNTs. The results enhance our understanding of the interactions between surfactant, defective CNTs and near-perfect CNTs and thus provide insight into the mechanism of CNT dispersion. Dispersions of “as-produced” short multi-walled carbon nanotubes (MWCNTs) in N,N-dimethylformamide were prepared by two different surfactant (Triton X-100) assisted methods: ultrasonication and ultrasonication followed by centrifugation, decanting the supernatant and redispersing the precipitate. Visual observation and UV–visible spectroscopy results showed that the latter method produce a more stable dispersion with higher MWCNT content compared to dispersions produced by ultrasonication alone. Transmission electron microscopy and Raman spectroscopic investigations revealed that the centrifugation/decanting step removed highly defective nanotubes, amorphous carbon and excess surfactant from the readily re-dispersible near-perfect CNT precipitate. This is contrary to other published findings where the dispersed MWCNTs were found in the supernatant. Thermogravimetric analysis showed that 95 % of Triton X-100 was removed by centrifugation/decanting step, and the remainder of the Triton X-100 molecules is likely randomly adsorbed onto the MWCNT surface. Infrared spectral analysis suggests that the methylene groups of the polyoxyethylene (aliphatic ether) chains of the residual Triton X-100 molecules are interacting with the MWCNTs.

Carbon fibre composites have been employed commercially for more than 50 years and their use is growing rapidly in the aerospace and automotive industries. In spite of its commercial success the relationship between the fibre structure and its physical properties are still poorly understood. This paper utilises a range of physical and chemical techniques to characterise both polyacrylonitrile and pitch based carbon fibre and highlights the heterogeneity of the fibre. Physical methods include nano-mechanical indentation whilst the use of focussed ion beam (FIB) milling for the preparation of flat surfaces for nano-indentation experiments has also been investigated. Chemical analysis involves inverse gas chromatography under finite concentration conditions and confocal Raman spectroscopy. The later includes both depth profiling showing the variation in structure from the surface to the core of the fibre and high spatial resolution (0.5 μm) mapping of the surface of the fibres.