Fiber Impregnation Research Articles

Study of fibre to fibre and ply to ply comingling technique for fabrication of natural fibre reinforced thermoplastic composites

Composite are made by using a reinforcement and a resin. Natural fibres are low cost, biodegradable and have good mechanical properties. Thermoplastic polymers are cheaper, recyclable and have good mechanical properties. The thermoplastic polymers (as a resin) are not commonly used due to their high viscosities which makes fibres’ impregnation difficult. In this study “fibre to fibre” and “ply to ply” commingling techniques were used for the fabrication of natural fibres reinforced thermoplastic composites. Jute and flax fibres were commingled with polypropylene using two types of structures i.e. woven (2/2 basket weave) and nonwoven. In addition to that fibre to matrix volume percentage was also varied (30% 40% 50% and 60%). Mechanical properties and surface morphology of the developed composites were studied. The results depicted that the woven composites have better mechanical properties than the nonwoven composites which may be because of the regular arrangement of fibres in woven composites. Furthermore, composites reinforced with flax exhibited better mechanical properties than the composites reinforced with jute. In addition to that, better mechanical properties were observed with fibre volume fraction of 30% and 40% which could be due to better impregnation of fibres with matrix.

Chemometrics optimization of an anionic carrier-mediated hollow fiber liquid-phase microextraction combined with HPLC-PAD for fluconazole extraction from plasma samples

In this research, we developed a method for fluconazole (FLU) quantification in plasma using carrier-mediated hollow fiber liquid-phase microextraction (HF-LPME). Briefly, the investigation of six solvents for fiber impregnation, two and three-phases modes of HF-LPME, and carrier-mediated HF-LPME were performed. A fractional factorial design 2(8–4) showed the influence of eight factors and it was followed by a central composite design with the most important three factors. Response surface and desirability test were also obtained. After optimization, the extraction condition consisted of the use of 500 µL of plasma samples containing FLU and 4.5 mL of NaOH solution (0.316 M) saturated with Na2SO4. Centrifugation was required for 15 min at 2200 g and 4 °C for sediment removal. A volume of 3.5 mL was transferred to extraction tubes and the fibers, already impregnated with 1-octanol and Adogen 464 (10 %), were placed in contact with the sample. Then, 60 µL of the acceptor phase were added inside the fiber, and stirring was performed at 1000 rpm for 40 min. Validation was performed in consonance with European Agency's Guideline on Bioanalytical Validation Methodology. The method showed linear range from 1.0 to 62.5 μg mL−1, recovery of 12 %, selectivity, no carryover effect, precision and accuracy within the recommended limits, and samples were stable in the stability studies performed. Finally, we confirmed the applicability of the obtained method at two samples obtained from a patient treated for neuromycosis with FLU. It is the first time that a microextraction technique is used for FLU analyses in plasma samples. The method showed good perspective of application in drug monitoring, without the need of large amounts of organic solvents that can be very harmful to health and environment.

Numerical Simulations of Carbon-Fibre Impregnation with a Polymer as an Anisotropic Permeability Medium.

The impregnation process of carbon fibres with polymers is challenging to model due to the system's complexity, particularly concerning the following aspects: the complex rheology of the polymeric matrices and the presence of solid, continuous fibres, both with anisotropic properties, and the interaction between solid and fluid, which can change the displacement of fibres into a cyclic dependence. In this work, an interesting approach was considered by setting the fibres as a porous medium whose properties were calculated with microscale/macroscale cycle modelling. In the microscale modelling stage, two main assumptions can be made: (i) a homogeneous distribution with a representative cell or (ii) a stochastic distribution of fibres. The solution to the abovementioned flow and fibre distribution problem can severely differ with only a slight change in a single parameter for a given set of processing parameters. Therefore, the influence of some of them during the fibre impregnation process was evaluated, allowing a shortcut for the polymer through a gap between fibres and the bottom wall of the extrusion die. The range of investigated values regarding the gap enables one to cover good impregnation conditions up to the occurrence of the shortcut and consequent poor impregnation quality. These studies were performed with numerical simulations with circa 126,000 degrees of freedom, considering the discretisation mesh elements and the unknowns (pressure and two velocity components).

Investigation on process window of 3D printed continuous glass fiber‐reinforced thermosetting composites

Abstract3D‐printed continuous fiber composites offer high strength in desired directions, which has attracted researchers' attention. In general, thermoset composites provide better results than their thermoplastics counterparts due to their higher modulus, low viscosity resin, better fiber impregnation, and proper adhesion to the reinforcing fibers. This study, examined the fabrication of continuous fiber‐reinforced thermoset composites (CFTCs) using 3D printing technology. This investigation focused on the optimization of process parameters for UV‐curable composites. Using systematic experimentation, the proper nozzle diameter (2.0 mm), print thickness (0.6 mm), and print speed (200 mm/min) were determined, resulting in the attainment of optimal fiber weight ratio and impregnation. The optimized CFTC exhibited an exceptional ultimate tensile strength of 276.26 MPa, exceeding existing literature data on printed short fiber composites. Additionally, under flexural loading conditions, an ultimate strength of 76.7 MPa was observed, which is characterized by a more ductile failure than a brittle fracture mode. The results of this research demonstrate the significant potential of 3D‐printed CFTCs and establish a robust process window for achieving exceptional mechanical properties. These findings hold promise for a wide range of applications demanding high‐strength composite materials.Highlights Continuous fiber reinforced thermoset composites successfully printed. Determination of a process window for printed CFTCs. The optimized CFTC exhibited a remarkable ultimate tensile strength of 276.26 MPa. Ultimate strength of 76.7 MPa was achieved under flexural loading.

An acrylic resin system for in‐situ pultrusion: Curing performances and rheology

AbstractIn recent years, the use of low viscosity and in‐situ polymerizable thermoplastic acrylic resins for advanced fiber reinforced composites has grown, specially to address the difficulty of fiber impregnation with high‐melt viscosity thermoplastic polymers. The present work investigated the curing kinetics, chemo‐rheology of an acrylic resin system for in‐situ pultrusion, and proposed the corresponding constitutive models. First, the curing kinetics was studied with the differential scanning calorimetry experiments. The viscosity development was obtained by a rheometer as functions of the degree of cure (DOC) and temperatures. The gelation point was acquired from the intersection point of storage and loss modulus curves through dynamic mechanical analysis test, which occurs at DOC of 0.65 determined by the cure kinetics model. Through the dynamic mechanical analysis, a four step cure hardening modulus model (modified CHILE approach) was proposed. The aforementioned models were applied in a case study to evaluate the influence of process parameters on the DOC, viscosity and physical behavior of the acrylic resin system in the pultrusion die.Highlights Material characterizations of an acrylic resin system are investigated. The cure kinetics and viscosity and elastic modulus models are proposed. A pultrusion case study is given.

Mechanical and morphological characterizations of epoxy composites reinforced with surface modified woven cotton structures using vacuum bagging technique

Woven fabric structures facilitate the mechanical interlacement of textile yarns for increased strength, which leads to more balanced mechanical properties in a composite. This study worked on epoxy matrix composites reinforced with surface-modified cotton fabrics of different woven structures. The composites were fabricated using the resin vacuum bagging technique and mechanically characterized for tensile, three-point bending, and impact properties. Surface modification was conducted by alkali treatment using a 6% concentration of sodium hydroxide (NaOH). The interfacial adhesion of the various fabric structures and epoxy matrix was examined using a scanning electron microscope (SEM). The results obtained show that surface-treated composites yielded improved mechanical properties than untreated composites, with improvements of up to 14.4%, 36.2%, and 26.7% for impact, flexural, and tensile strengths, respectively. The different woven structures also significantly affected the mechanical performance of the composite. The composites of plain, herringbone, and twill woven structures presented better mechanical properties compared to the other woven composite structures in that order. The plain-woven composite structure, respectively, had the maximum impact, flexural, and tensile strengths of 80.03 KJ/mm2, 38.6 MPa, and 43.7 MPa. This was closely followed by the herringbone and twill-woven composite structures. SEM results revealed complete impregnation of fibers and a strong interfacial relationship between the thermoset matrix and the treated cotton fabrics in the composite laminate structures produced via the vacuum bagging technique. In conclusion, the study indicated that different weave structures and fiber surface treatments, as well as the vacuum bagging technique used, are of significant importance in enhancing the overall mechanical performance of woven fabric composites.

Properties of Ramie (Boehmeria nivea (L.) Gaudich) Fibers Impregnated with Non-Isocyanate Polyurethane Resins Derived from Lignin.

The textile industries need an alternative to cotton since its supply is unable to keep up with the growing global demand. The ramie (Boehmeria nivea (L.) Gaudich) fiber has a lot of potential as a renewable raw material but has low fire-resistance, which should be improved. In this work, the objectives were to investigate the characteristics of lignin derived from black liquor of kraft pulping, as well as the properties of the developed lignin-based non-isocyanate-polyurethane (L-NIPU), and to analyze ramie fiber before and after impregnation with L-NIPU. Two different formulations of L-NIPU were impregnated into ramie fiber for 30, 60, and 90 min at 25 × 2 °C under 50 kPa. The calculation of the Weight Percent Gain (WPG), Fourier Transform Infrared Spectrometer (FTIR), Rotational Rheometer, Dynamic Mechanical Analyzer (DMA), Pyrolysis Gas Chromatography Mass Spectrometer (Py-GCMS), Universal Testing Machine (UTM), and hydrolysis test were used to evaluate the properties of ramie fibers. The result showed that ramie fiber impregnated with L-NIPU produced higher mechanical property values and WPG than non-impregnated ramie fiber. There is a tendency that the longer impregnation time results in better WPG values, FTIR intensity of the urethane group, thermomechanical properties, crystallinity, and mechanical properties of ramie fiber. However, the use of DMC and HMT cannot replace the role of isocyanates in the synthesis of L-NIPU because it produces lower heat resistance than ramie impregnated using pMDI. Based on the results obtained, the impregnation of ramie fiber with L-NIPU represents a promising approach to increase its wider industrial application as a functional material.

Influence of Molecular Weight on Thermal and Mechanical Properties of Carbon-Fiber-Reinforced Plastics Based on Thermoplastic Partially Crystalline Polyimide.

For the first time, a study of the influence of the molecular weight of the thermoplastic partially crystalline polyimide R-BAPB on the thermophysical and mechanical properties of carbon plastics was presented. The molecular weight of polyimide was determined using the method of light scattering and the study of the intrinsic viscosity of polyamic acid solutions. To obtain CFRPs, the uniform distribution of polyimide powder on continuous carbon fibers via electrostatic spraying and further hot calendering and pressing were applied. The study of the structure of the obtained carbon plastics via scanning electron microscopy has shown that the growth of the molecular weight of polyimide prevents the impregnation of carbon fiber with the introduced polyimide. Moreover, an increase in the molecular weight of polyimide leads to a rise in glass transition and thermal decomposition temperatures up to 590 °C, while the degree of crystallinity of CFRP falls. Nonetheless, raising the molecular weight from 22,000 to 70,000 g/mol of a binder polymer improves the interlayer fracture toughness G1C by more than five times.

3D printing of vegetable yarn-reinforced polymer components

Additive manufacturing has rapidly transformed over the years, moving from simply prototyping to producing objects and structures with advanced materials. The process, also known as 3D printing, enables complex shapes to be generated with great freedom of creation and low waste of resources. Although polymers have been widely used for the manufacture of small objects, the poorer mechanical properties and time required for 3D printing make the technique impractical for the production of real size structural components. This paper presents the development of a larger-diameter head nozzle for the manufacturing of a polymer-based material reinforced with continuous yarns. To address this issue, a continuous yarn reinforcing method was developed, utilizing a modified Fused Filament Fabrication (FFF) hotend adapted to the in-nozzle impregnation of vegetable fibers (i.e., a process by which the yarn and matrix are joined in a single nozzle), such as jute, ramie, and sisal, combined with polylactic acid (PLA) to produce bio-based printed filaments with diameters up to 3 mm. The combination of these materials aims to create printed composites with better mechanical properties and, above all, to meet the environmental need for low-energy biodegradable materials from natural sources that ultimately contribute to reduce the sector's ecological footprint. It was observed that the reinforced samples achieved gains of 28.6% in strength and 28.9% in stiffness in comparison to the unreinforced matrix, using fiber contents up to 48.2% that reduce the polymer utilization per printed volume. The feasibility of the production of multilayer components using the developed method was also confirmed for different types of reinforcement and printing paths.

Design and fabrication of high-performance 3D printed continuous flax fibre/PLA composites

The mechanical properties of 3D-printed continuous plant fibre-reinforced poly(lactic) acid (PLA) composites are insufficient due to the low fibre volume fraction (∼30 %). Further increase of fibre volume fraction of composites by reducing the line width may result in a composite with low fibre impregnation degree or the clogging of printer nozzle because of the twisted nature and uneven diameter of plant yarns, which also degrades the mechanical properties. This study proposed a method to obtain 3D printed continuous flax fibre reinforced composites (CFFRCs) with a high fibre volume fraction and excellent mechanical performance by statistical analysis of the dimensions of flax fibre yarns as well as surface modification. The CFFRCs were printed by a fibre prepreg-based 3D printing method, and an in-situ impregnation method was also used to prepare CFFRCs for comparison. The results showed that the CFFRCs by the fibre prepreg method had a fibre volume fraction of 44.1 % and a void content of ∼1.9 % due to the high impregnation degree. Correspondingly, the tensile modulus and strength of the CFFRCs were the highest among the existing reported values of the composites made by 3D printing and even greater than those of the CFFRCs with a fibre volume fraction of ∼51.4 % prepared by the in-situ impregnation method.

Evaluations of Sisal Fiber as Biosorbent for online Preconcentration and Determination of Cu and Mn coupled to MP AES using the Analytical Greenness Metric Approach

Biorsorbents can be used to pack minicolumns for the preconcentration of trace elements and thus improve the detection limits of some techniques. A biosorbent is efficient when presents binding sites as carbonyls, amines, and carboxylic groups, among others. Thus, natural materials as the sisal fiber (Agave sisalana) may be a good candidate. Sisal fiber demonstrated good performance for Cu preconcentration when it was impregnated with alizarine fluorine blue (AFB). However, very good results were reported for the first time by our group with this column, without the use of additional reagents for both, Mn and Cu determinations in water samples by using microwave plasma atomic emission spectroscopy (MP AES). In this paper a comparison of the sisal fiber preparation with and without impregnation with AFB is presented and discussed in terms of the figures of merit, including precision, trueness, limits of detection and quantification. In addition to that, the number of determinations without the need of replacement of the solid phase was evaluated. Results demonstrated that the impregnation of sisal fiber with AFB does not leads to an improvement in the analytical performance. Analytical Greenness Metric Approach (AGREE) was used to evaluate the greenness of both methods and results obtained were similar. Despite this, the method without impregnation of the fiber has some remarkable advantages, that contributes to Green Analytical Chemistry (GAC), related to the lifetime of the sorbent, not considered in the AGREE tool.

Alpaca fiber impregnated with alizarine and indigo dyes in a process using supercritical carbon dioxide

Supercritical carbon dioxide (scCO2) is an alternative medium for a drastic reduction of water for the impregnation of synthetic and natural fibers, especially azoic dyes. In this study, we evaluated the impregnation of alpaca fibers with alizarine and indigo dyes in a process with scCO2, using DMSO as a cosolvent for the dyes. The scCO2 flow rate ranged from 8 to 17.0 g/min over 90 min through a 1000 mL impregnation autoclave, and the amounts of dye:Al2(SO4)3 loaded were 15%:55% of the fiber weight, respectively. Impregnation was evaluated between 308.15 −363.15 K and 22.40 −13.37 MPa, and the products were characterized by FTIR spectroscopy. The highest impregnation obtained was 142.05 mg alizarine/g fiber at 311.15 K and 17.9 MPa and 260.80 mg indigo/g fiber at 329.15 K and 17.5 MPa. Color fastness analysis revealed that the colored fibers were resistant to water washing in the range of 4–5, a commercially accepted level for the fiber.

Preparation and characterization of non-isocyanate polyurethane resins derived from tannin of Acacia mangium bark for the modification of ramie fibers

Abstract The purpose of this research was to create bio-based non-isocyanate polyurethane (Bio-NIPU) resins derived from the tannin of Acacia mangium Willd. bark for the impregnation of ramie fibres (Boehmeria nivea L.) and to investigate the properties of impregnated fibres. Tannin was extracted from the bark of A. mangium using hot water. Tannin-bio-NIPU resin was created using dimethyl carbonate and hexamine. Based on the findings, it is possible to conclude that tannin extract from the bark of Acacia mangium can be used effectively as a renewable alternative to toxic polyols in the development of tannin-Bio-NIPU resins. FTIR spectroscopy was used to confirm the urethane bond formed on the tannin-Bio-NIPU resins. Thermal and mechanical analysis were used to investigate the properties of tannin-Bio-NIPU resins and ramie fibres before and after impregnation. This study shows that the impregnation time of ramie fiber using tannin-Bio-NIPU resins is 30 minutes. The reaction between tannin-Bio-NIPU resins with ramie fiber forms the C=O urethane group as confirmed by FTIR Spectroscopy. The characterization results show that tannin-Bio-NIPU resins has ability to modify ramie fiber via impregnation in order to increase its mechanical properties, thus enhancing its potential for wider industrial application as a functional material.

Effect of Micromolecules and Macromolecules on the Environmentally Friendly Impregnation Solution for High-Performance Rubber Composites Compared with Traditional RFL Impregnation

In this paper, a novel resorcinol-formaldehyde-free and environmentally friendly adhesives for polyester (PET) fiber impregnation treatment were compounded successfully. First, a network structure was formed by reacting micromolecular and water-soluble glycerol triglycidyl ether (GLTE) and triethylenetetramine (TETA). Then, this was mixed with latex in order to prepare an impregnation solution glycerol triglycidyl ether-triethylenetetramine-butyropyridine latex system (GTL), which can replace the toxic components (resorcinol and formaldehyde) of the resorcinol-formaldehyde-latex (RFL) impregnation system. Similarly, the macromolecular epoxy resin E-51-triethylenetetramine-butyropyridine latex system (ETL) and the traditional RFL impregnation system were also prepared in order to compare with the GTL. Further, the reaction conditions of the impregnation system, the surface chemical composition and interfacial properties were characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and peeling strength, respectively. The results showed that the peeling adhesion performance between the GTL-modified PET fabric and the rubber (38.5% higher than that of the ETL impregnation solution) was comparable to that of the RFL impregnation system because of micromolecular and more active GLTE. This study provides new insights into the interface design of PET/rubber composites and will facilitate the development of PET/rubber composites.

Experimental and Simulative Analysis of the Pressure Development in a Closed Injection Pultrusion Process with Multiple Chamber Geometries

The use of innovative higher-performance highly reactive resin systems requires an enhancement of the established method of fiber impregnation (open bath) towards closed resin-injection pultrusion (CIP), due to the short pot life of the resin systems. The result is that the open bath is developed into a closed injection and impregnation chamber ("ii-chamber"). In this study, three parameters-resin viscosity, opening angle and opening factor at the injection point on the ii-chamber-are varied, each in three stages. For each set of parameters, a pultrusion trial is conducted and the process pressures in the ii-chamber and pultrusion die measured. This enables direct feedback via the process conditions of the as yet uncured composite. The data obtained are used to validate a newly developed simulation model. The model is based on Darcy's law, which has been extended to take fiber movement into account and thus represent the resulting pressure increase in the die. The flexible ii-chamber and die concept enhance our understanding of the processes taking place in the die system. The sensitivity of the process pressures can be shown for the three influencing variables. The experiment shows that of the three influencing variables investigated, viscosity has the greatest sensitivity to pressure development. In general, it can be said that over the length of the pultrusion die system, the pressure level increases across the three measuring points.

Mechanical, Thermal Properties and Void Characteristics of Bamboo Fiber-Reinforced Epoxy Resin Composites Prepared by Vacuum-Assisted Resin Transfer Molding Process

ABSTRACT This study aimed to examine the effect of epoxy resin (EP) systems on the impregnation of bamboo fibers (BFs) by EP and the properties of BF/EP composites prepared by vacuum-assisted resin transfer molding (VARTM) process. BF preforms obtained by solution suspension method were used as reinforcement, and epoxy/anhydride system (EP-1), epoxy/amine system (EP-2) and two-component epoxy system (EP-3) were employed as matrix; on this basis, BF/EP-1, BF/EP-2 and BF/EP-3 composites were prepared by VARTM. The physical, mechanical and thermal properties and void characteristics of BF/EP composites were characterized. The results showed that EP-1 with a viscosity of 265 mPa·s at 23°C and an operating time of room temperature without curing was beneficial for the EP-1 to impregnate BFs adequately and uniformly. The incorporation of BFs into EP-1 significantly improved the flexural, shear and impact properties, thermal properties and interface properties of EP-1. Moreover, the properties of BF/EP-1 composites were better than those of BF/EP-2 and BF/EP-3 composites. Three-dimensional X-ray microscopy scans revealed that the volume and distribution of voids in the BF/EP composites differed significantly depending on the EP systems, and the percentage of void volume in the BF/EP-1 composites was only 0.14% in 3D reconstruction models.

Eco-Friendly Tannin-Based Non-Isocyanate Polyurethane Resins for the Modification of Ramie (Boehmeria nivea L.) Fibers.

This study aimed to develop tannin-based non-isocyanate polyurethane (tannin-Bio-NIPU) and tannin-based polyurethane (tannin-Bio-PU) resins for the impregnation of ramie fibers (Boehmeria nivea L.) and investigate their mechanical and thermal properties. The reaction between the tannin extract, dimethyl carbonate, and hexamethylene diamine produced the tannin-Bio-NIPU resin, while the tannin-Bio-PU was made with polymeric diphenylmethane diisocyanate (pMDI). Two types of ramie fiber were used: natural ramie without pre-treatment (RN) and with pre-treatment (RH). They were impregnated in a vacuum chamber with tannin-based Bio-PU resins for 60 min at 25 °C under 50 kPa. The yield of the tannin extract produced was 26.43 ± 1.36%. Fourier-transform infrared (FTIR) spectroscopy showed that both resin types produced urethane (-NCO) groups. The viscosity and cohesion strength of tannin-Bio-NIPU (20.35 mPa·s and 5.08 Pa) were lower than those of tannin-Bio-PU (42.70 mPa·s and 10.67 Pa). The RN fiber type (18.9% residue) was more thermally stable than RH (7.3% residue). The impregnation process with both resins could improve the ramie fibers' thermal stability and mechanical strength. The highest thermal stability was found in RN impregnated with the tannin-Bio-PU resin (30.5% residue). The highest tensile strength was determined in the tannin-Bio-NIPU RN of 451.3 MPa. The tannin-Bio-PU resin gave the highest MOE for both fiber types (RN of 13.5 GPa and RH of 11.7 GPa) compared to the tannin-Bio-NIPU resin.

Fabrication of chitosan-flax composites with differing molecular weights and its effect on mechanical properties

An aqueous fabrication method is investigated for a composite reinforced with chitosan and flax fibers. The composite is characterized structurally, mechanically and chemically. A strong influence of molecular weight (MW) is identified on the composite properties. A strong fiber-matrix interface, which is associated with porosity and effective fiber impregnation, is achieved by applying low molecular weight (LMW) solution followed by casting using LMW or medium molecular weight (MMW) solution. Porosity is analyzed using μ-CT analysis. Increasing porosity with increasing molecular weight results in a decline of the tensile and flexural properties of the composites. The chitosan-flax composites have a low density compared to synthetic and natural fiber composites, which is a competitive advantage as a replacement material for particle board or plyboard in suspended ceilings, furniture compartments, sports or leisure equipment. A multiscale simulation is carried out to compute the directional effective elastic properties and predicts a potential 21% improvement of the tensile modulus if the process is optimized. This work shows the potential of chitosan-flax composites as a sustainable green material with an aqueous fabrication procedure and useful mechanical properties.

1147 MORPHO-FUNCTIONAL EVALUATION OF 3MG/KG ICV-STZ RAT SHOWED SPORADIC ALZHEIMER'S LIKE PATHOLOGY WITH PROGRESSIVE DEMENTIA

Abstract Background Intracerebroventricular streptozotocin (ICV-STZ) injection is among the best animal models to simulate sporadic Alzheimer’s disease (sAD). Abnormality in brain insulin signalling, neurodegeneration, neuroinflammation, cholinergic damage, mitochondrial dysfunction, genetic abnormality, respiratory problem, oxidative stress, gliosis, sleep disturbances are associated with cognitive abnormalities seen in ICV-STZ injected rats. Available experimental evidence has used varying doses of STZ (<1 to 3mg/kg) and studied its effect for different study durations, ranging from 14-21 (short), 30-42 (mild), 90-105 (moderate) and 250-270 (long) days. These studies indicated that 3mg/kg of body-weight is the optimum dose for inducing sAD in the rodents. However, studies on the pathological process with related the morphological and functional abnormalities reported were illusive. Objective/Method Hence in the present study, we have investigated the morpho-functional changes after 3mg/kg ICV-STZ treatment with a follow-up of two months in 54 male Wistar rats (ethical no. 937/IAEC/PhD-2016). Results Exhibited a spatial, episodic and avoidance memory decline and increase in anxiety (p<0.05) in ICV-STZ group progressively with time from 15th day to 60th day post-injection. Morphometry showed hippocampal atrophy with CA1, CA3 layer thinning (p ≤0.01) and loss of neurons (p<0.0001) associated with third ventricular enlargement (p= 0.007) in ICV-STZ rats versus sham, along-with extracellular amyloid plaque in AD rats with Congored staining. In addition, spine morphometry with Golgi-Cox impregnation of mossy fibre showed a reduction of spine density in AD group versus control and sham group (p<0.0001). Finally, immunohistochemistry of GSK3ß, PI3K and mtCOX-1 antigen in coronal sections revealed an increase in mean intensity of GSK3ß and decrease in PI3K and mtCox-1 in brain areas associated with limbic system in ICV-STZ group on 60th day. Conclusion These findings suggest progressive dementia and anxiety in 3mg/kg STZ treated rats, which may be due to hippocampal atrophy, amyloidopathy, ventricular enlargement, synaptic dysfunction and deficits in energy homeostasis of brain.

Topology and structure analysis of carbon fiber-reinforced polyimide composites

This paper describes the production of carbon fiber / high-performance polyimide prepregs and the study of prepreg samples quality by scanning electron microscopy, atomic-force electron microscopy and scanning ion-conductance microscopy. The prepreg samples were produced using a laboratory-designed setup by impregnation of carbon fiber with a polyimide solution. The study of the prepreg structure made it possible to establish the connection between polymer matrix composition and quality of carbon fiber impregnation. Thus, the study shows that the polymer matrix composition containing aliphatic fragment and quaternary carbon atom produces the best performance prepreg suitable for FDM 3D printing.