Composites

Materials of acryloide type are very often used in conservation and restoration of ceramic materials as adhesives, consolidants and protective coatings. As they do not have enough strength by themselves to satisfy more demanding interventions, inorganic particles were added as reinforcement in order to improve their mechanical properties. In the present work composite materials with matrix made from mixture of two acryloid copolymers, Paraloid B-72 and B-48N, were tested for extreme service condition that were simulated by exposing the samples to cavitation resistance.

The growing concerns about the environment and energy have driven the widespread adoption of new lightweight materials such as polymer composites in many industrial sectors, crucial issues being performance, cost efficiency, and multifunctionality (Krawczak, 2019). Among them, thermosetting matrix composites offer not only many advantages such as high specific stiffness and strength and their consolidated use in primary aircraft structures but also technical issues such as long processing times, limited fracture toughness, reduction of mechanical properties in the presence of water and solvents, and difficulty of end-of-life treatment (Krawczak, 2011). A key cultural problem is associated with the need of a chemical reaction during part fabrication performed in mechanical/aerospace/naval industries.

Although the use of thermoplastic matrix composites in aeronautic structures has been proposed since the second half of the 80s (Nguyen and Ishida, 1987; Maffezzoli et al., 1989), their first application was at the beginning of the third millennium with the wing leading edge of Airbus A380 (Offringa, 2005). Their demand is continuously increasing (JEC Observer, 2020) since they offer many advantages such as high toughness, long storage time, easy repairing and recycling, higher performances in hot-wet conditions, and ability to be thermoformed and heat-welded. However, manufacturing issues such as high processing temperature, fiber impregnation, and warpage still need a deeper knowledge (Advani and Hsiao, 2012). Thermoplastic composites can play a key role in the 21st century industry as new materials are emerging day by day, as manufacturing processes are evolving to meet the severe industrial requirements of performance, production, and multifunctionality (Advani and Hsiao, 2012; Boisse, 2015), and as sophisticated numerical simulation tools are making virtual prototyping and engineering more reliable than ever (Binétruy et al., 2015; Boisse, 2015). In that field, innovation is multifaceted and may come either from the constitutive materials (high-performance engineering thermoplastic matrices, commingled semipreg of fibers/thermoplastics, self-healing, bio-based or biodegradable matrices, natural or thermoplastic fibers, 3D textile reinforcement…) or from the manufacturing processes (automated out-of-autoclave processes, hybridization/coupling of technologies, additive manufacturing, hybrid welding…). Moreover, thermoplastic composites allow for automated, high-speed mass production with reduced need for secondary operations (Mafeld, 2014), creating increased interest in the industry for various applications: aerospace and defense, automotive and rail transportation, construction and building, energy, oil and gas, sporting goods, drones, etc. Also, thermoplastic composites offer an interesting recycling potential using mechanical, thermal, or chemical processes (Oliveux et al., 2015). As thermoplastics, it is quite easy to recycle them by regrinding, compounding/blending, and reprocessing; additionally, they are at the forefront of current industrial scale-up attempts of chemical recycling, making it possible to recover not only fibers but also feedstock or original monomers which can eventually be re-polymerized to produce new polymers.
This Research Topic focuses on the latest advances and developments of fiber-reinforced thermoplastics, mainly referring to continuous fiber-reinforced composites and of related processing technologies. A collection of seven articles addresses some challenging issues related to advanced manufacturing processes, such as consolidation by compression molding (Ayadi et al.), injection-overmolding (Akkerman et al.), reactive pultrusion (Zoller et al.), joining by ultrasonic (Villegas) or induction (Scarselli et al.) welding, as well as solid-state drawing (Walker et al.) or electrospinning (Sessini et al.) of fibers. Numerical modeling and simulation, and performance assessment through advanced characterization techniques, correlating microstructure and properties, are also addressed. These papers highlight how thermoplastic matrix composites can be processed, adopting a completely different paradigm in comparison to thermosetting matrix ones, the former not requiring a reaction to set the properties but complex thermal cycles, often performed in a short time span.
The Guest Editorial team is confident that this collection of papers will benefit a large community in research and application of advanced thermoplastic composite materials so as to further advance along the pathway toward sustainability, performance, and competitiveness.

This short communication extends earlier modelling of the tensile strength and failure strain of jute technical fibres. A maximum likelihood estimate (MLE) model, a linear model and a natural
logarithmic interpolation model (NLIM) are compared. The NLIM model is found to give superior predictions.

The formation of solid solutions of the type [Ba(HOC2H4OH)4][Ti1−x Gex (OC2H4O)3] as Ba(Ti1−x /Gex )O3 precursors and the phase evolution during thermal decomposition of [Ba(HOC2H4OH)4][Ti0.9Ge0.1(OC2H4O)3] (1) are described herein. The 1,2-ethanediolato complex 1 decomposes above 589 °C to a mixture of BaTiO3 and BaGeO3. A heating rate controlled calcination procedure, up to 730 °C, leads to a nm-sized Ba(Ti0.9/Ge0.1)O3 powder (1a) with a specific surface area of S = 16.9 m2/g, whereas a constant heating rate calcination at 1,000 °C for 2 h yields a powder (1b) of S = 3.0 m2/g. The shrinkage and sintering behaviour of the resulting Ba(Ti0.9/Ge0.1)O3 powder compacts in comparison with nm-sized BaTiO3 powder compacts (2a) has been investigated. A two-step sintering procedure of nm-sized Ba(Ti0.9/Ge0.1)O3 compacts (1a) leads, below 900 °C, to ceramic bodies with a relative density of ≥90%. Furthermore, the cubic ⇆ tetragonal phase transition temperature has been detected by dilatometry, and the temperature dependence of the dielectric constant (relative permittivity) has also been measured.

Boron doped and undoped Poly(vinyl) alcohol/Zirconium-yttrium acetate (PVA/Zr-Y) nanofibers were prepared by electrospinning using PVA as a precursor. The effect of boron doping was investigated in terms of solution properties, morphological changes and thermal properties. The effect of boron doping on calcined yttria stabilized zirconia (YSZ) fibers were evaluated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy analysis. XRD
analysis revealed varying amounts of monoclinic and tetragonal zirconia present in the undoped fibers calcined at 800oC. The average crystallite sizes of the undoped YSZ were increased from 9.28 to 22.79 nm with calcining temperature increasing from 250 to 800 °C. The crystallite size was enhanced with boron doping. The systematic evolution of morphological features in the spun and the processed fibers were employed by scanning electron microscopy.

Premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder was analyzed as matrix in this research. Gas atomized powder Al-9Si with
20% volume fraction of SiC particles was used as reinforcement and added into the alloy with varied concentration. Mix
powders were compacted by dual action press with compaction pressure of 700 MPa. High volume fraction of SiC particles
gave lower green density due to resistance of SiC particles to plastic deformation during compaction process and resulted voids
between particles and this might reduce sinterability of this mix powder. Sintering was carried out under ultra high purity
nitrogen gas from 565◦
-580◦C for 1 hour. High content of premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder gave better sintering
density and reached up to 98% relative. Void between particles, oxide layer on aluminum powder and lower wettability between
matrix and reinforcement particles lead to uncompleted liquid phase sintering, and resulted on lower sintering density and
mechanical properties on powder with high content of SiC particles. Mix powder with wt90% of Alumix 431D and wt10% of
Al-9Si-vf20SiC powder gave higher tensile strength compare to another mix powder for 270 MPa. From chemical compositions,
sintering precipitates might form after sintering such as MgZn2, CuAl2 and Mg2Si. X-ray diffraction, DSC-TGA, and SEM
were used to characterize these materials.

Machining Surface integrity a b s t r a c t Surface topography induced by precision machining is critical for component performance. Four representative surface topographies of turned and ground surfaces were prepared at "extreme" machining conditions (gentle and abusive) and compared in terms of 3-dimensional (3D) surface features of amplitude, area and volume, spatial, and hybrid parameters. The 3D surface topography maps revealed the anisotropic and repeatable nature of a turned surface which was in sharp contrast with the random and isotropic nature of a ground surface. In general, a gentle turned surface has higher values of amplitude parameters (arithmetic mean, root mean square, maximum height of summits, maximum depth of valleys, and 10-point height) than an abusively turned surface, whereas the opposite was true for the ground counterparts. Only the gentle ground surface has a negative skewness which means that the topography distribution is more biased towards the valley side. The larger kurtosis value of the abusively ground surface implies a more peaked surface topography. The gentle ground and abusively turned surfaces have a much larger bearing area ratio and therefore better bearing capacity than the gentle turned and abusively ground ones. The abusively ground surface has higher fluid retainability than other surfaces in terms of mean void volume. However, surface performance, such as wear and fatigue is dependent both on surface topography as well as mechanical property and relies on the dominance of the individual aspect.

While preparing the composite preform in the powder metallurgy Lab, the various defects due to porosity, open crack and residual stresses are possible. This may lead to poor life and strength of materials. It is difficult to predict the defects in the form of pores physically in the powder metallurgy Lab. To simplify this kind of problem, the Scanning Electron Microscope (SEM) images are generated from the powder composites and are segmented using region growth approach to find the distribution of pores. Normally, the composite preforms are being produced through various processes like mechanical milling, mixing, compaction, sintering and hot extrusion. In this study, Cu–(5–20%) W composite preforms, with a preform density of 94% are prepared. The pore size in term of coverage area, perimeter during different sintering atmospheres are derived. Further, the porosity is reduced during extrusion process. The results of SEM images are compared before and after sintering and extrusion process. This kind of work will aid the manufacturing process of material parts in predicting their strength and life time.

A composite is defined as a multiphase material and composition of material differing in composition, which remain bonded together, but retain their identities and properties, without going to any chemical reaction. Composite is engineered to meet specific application, performance and specific needs. Ecological concerns have resulted in renewed interest in natural materials. Development of natural fibers reinforced composites is highly attractive research lines. Green composite combines plant fibres with natural resins to creat natural composite materials. Biomaterial composites are made from hemp, kenaf, sisal, soybean, etc. Natural fibres are emerging as low cost, lightweight and apparently environmentally superior alternative to synthetic fibres. The resins and fibres used in the green composites are biodegradable, when they dumped, decomposed by the action of microorganisms. They are converted into the form of H2O and CO2. These H2O and CO2 are absorbed into the plant systems. Environment-friendly green composites were fabricated from a starch-based, dispersion-type biodegradable resin and cellulose fibres. The mixture of the dispersion-type biodegradable resin and cellulose fibres were blended well by using a home-use mixer and a stirrer, and then dried in air or in a vacuum. Composites were prepared by conventional hot pressing at a constant temperature of 140° degree celsius and at pressures of 10 to 50 MPa their flexural strength as well as flexural modulus increased with increasing the moulding pressure.
Keywords: Composites ,Reinforce, biodegradable, Biomaterial,

Natural cellulose fibers have been obtained from the bark of cotton stalks and the fibers have been used to develop composites. Cotton stalks are rich in cellulose and account for up to 3 times the quantity of cotton fiber produced per acre. Currently, cotton stalks have limited use and are mostly burned on the ground. Natural cellulose fibers obtained from cotton stalks are composed of approximately 79% cellulose and 13.7% lignin. The fibers have breaking tenacity of 2.9 g per denier and breaking elongation of 3% and modulus of 144 g per denier, between that of cotton and linen. Polypropylene composites reinforced with cotton stalk fibers have flexural, tensile and impact resistance properties similar to jute fiber reinforced polypropylene composites. Utilizing cotton stalks as a source for natural cellulose fibers provides an opportunity to increase the income from cotton crops and make cotton crops more competitive to the biofuel crops.

In this work, the effect of particle type and distribution on the bending behavior of glass particle reinforced epoxy composite beams are studied analytically. Euler Bernoulli and Timoshenko Beam deflection results are compared with numerical deflections obtained by Fem Analysis. Bending analysis of particle reinforced composites are studied for graded distribution bottom to top. The composite elastic modulus variation with thickness is found according to micro-CT based modeling for different particle types and graded distribution. The effects of the graded distribution of particles are considered by functionally graded beam equation formulations. Local stress distribution along thickness is found by using finite element analysis. The relation between the stress results and particle type is discussed at a macro scale.

The properties of porous hydroxyapatite (HA) bioceramic produced by heat treatment (annealing) of bovine bone were evaluated over temperatures between 400 °C and 1200 °C. The annealed body was characterized by thermal analysis (thermogravimetric analysis (TG)/differential thermal analysis (DTA)), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transformed infrared (FTIR) spectroscopy. The XRD results showed that the annealing process enhanced the crystallinity of HA phase in the bone matrix particularly when annealed above 700 °C. There was no secondary phase formation in bones annealed between 600 °C and 1000 °C. However, decomposition of HA to β-tricalcium phosphate (TCP) was observed for samples heat-treated at 1100 °C and 1200 °C. The FTIR spectra and the TG/DTA thermogram of as-received bovine bone indicated the presence of organic compounds, which upon annealing at temperatures above 600 °C was completely removed from the matrices. Bovine bone annealed between 800 °C and 1000 °C revealed the characteristics of a natural bone with the interconnecting pore network being retained in the structure.

http://www.sciencedirect.com/science/article/pii/S0272884206001581

A series of poly(urea-formaldehyde) (PUF) microcapsules filled with dicyclopentadiene (DCPD) was successfully prepared by in situ polymerization. The effect of diverse process parameters and ingredients on the morphology of the microcapsules was observed by SEM, optical microscopy (OM) and digital microscopy. Different techniques for the characterization of the chemical structure and the core content were considered such as FT-IR and (1)H-NMR as well as the characterization of thermal properties by DSC. High yields of free flowing powder of spherical microcapsules were produced. The synthesized microcapsules can be incorporated into another polymeric host material. In the event the host material cracks due to excessive stress or strong impact, the microcapsules would rupture to release the DCPD, which could polymerize to repair the crack.

ABSTRACT: Accurate measurement of permeability is critical for fluid flow modeling in porous media. Various experimental methods devised to measure permeability as a porous material property in composites are reviewed. Liquid flow and gas flow methods of permeability measurement for in-plane and transverse directions specifically for fiber-reinforced composites are discussed, as well as issues related to these methods and some associated permeability models. Alternative methods of permeability determination based on cross transport phenomenon are reviewed as well.

Introduction: This study aimed to compare the Shear Bond Strength (SBS) of two bulk-fill
composites versus a conventional resin composite.
Materials and Methods: In this study, 60 sound extracted human premolars were selected and
sectioned horizontally from one-third of the coronal crown to expose dentin using a low-speed
cutting saw. The dentin bonding agent was applied to all specimens, then they were randomly
divided into three groups based on their corresponding composites: Group I: Bulk-fill packable
(x-tra fil, Voco, Germany); Group II: Bulk-fill flowable (x-tra base, Voco, Germany); and
Group III: Conventional (Grandio, Voco, Germany). Subsequently, composite samples with
a diameter of 2.5 mm and height of 4 mm were prepared. Following thermocycling (1500
cycles, 5°C -55°C), SBS testing was performed by a universal testing machine. Then, the
specimens were examined for the type of fracture (adhesive, cohesive, or mixed) under a
stereomicroscope at 20X magnification. Data were analyzed using 1-way ANOVA and Tukey
post-hoc test in SPSS.
Results: The highest bond strength was observed in group III (52.99±6.07) and the lowest
bond strength was observed in group II (49.11±4.86). There was no statistically significant
difference between the packable and flowable groups in terms of SBS (P=0.19). Statistically
significant differences were detected between group I and group III (P=0.005) as well as group
II and group III (P=0.000). The majority of the fractures observed in all three groups were of
adhesive type.
Conclusion: Conventional composites produced significantly better results in comparison
with bulk-fill composites as far as SBS was concerned. Therefore, it is advisable to continue
the use of bulk-fill materials incrementally in dental treatment.

Preparation of polypropylene (PP)/waste tyre dust (WTD) blends with addition of dicumyl peroxide (DCP) and N,N0-mphenylenebismaleimide (HVA-2) (PP/WTDP-HVA2) was described. The blends were characterized based on their tensile
properties, swelling resistance and morphology, as well as thermal properties. The results reveal that the presence of both
chemicals in PP/WTDP-HVA2 blends brought about noticeable improvements in tensile properties, swelling resistance and
interfacial adhesion. The thermal stability was also improved, indicating existence of some chemical interaction between
WTD and the PP matrix in the presence of both DCP and HVA-2 during processing. The results imply that both chemicals
had great influences on WTD destabilization, leading to the enlargement and intensification of the copolymer formation
and, hence, improved the interfacial adhesion between WTD and the PP matrix. A competing reaction mechanism that
may contribute to the property enhancement of PP/WTDP-HVA2 blends was proposed.

— Mechanical and thermo-analytical analysis carried out on the composites. In order to determine the relationships between structure and properties of composite, it is necessary to carry out different measurements. The tests were: tensile test, hardness test, thermal conductivity SEM, DSC and DMA. The results showed that the mixtures were inhomogeneous. The tensile and hardness test resulted that the composite has stronger structure and an increase in the strength values. From the thermo-analytical analysis the corn cob additive effect in the composite structure can be observed. The result of the DMA shows that the additive works as inactive filler, and does not change the glass transition temperature of the rigid PVC foam.