Surface Layer Of Fibers Research Articles

A Highly Sensitive and Stretchable Core-Shell Fiber Sensor for Gesture Recognition and Surface Pressure Distribution Monitoring.

This work reports a highly-strain flexible fiber sensor with a core-shell structure utilizes a unique swelling diffusion technique to infiltrate carbon nanotubes (CNTs) into the surface layer of Ecoflex fibers. Compared with traditional blended Ecoflex/CNTs fibers, this manufacturing process ensures that the sensor maintains the mechanical properties (923% strain) of the Ecoflex fiber while also improving sensitivity (gauge factor is up to 3716). By adjusting the penetration time during fabrication, the sensor can be customized for different uses. As an application demonstration, the fiber sensor is integrated into the glove to develop a wearable gesture language recognition system with high sensitivity and precision. Additionally, the authors successfully monitor the pressure distribution on the curved surface of a soccer ball by winding the fiber sensor along the ball's surface.

Self-encapsulated ionic fibers based on stress-induced adaptive phase transition for non-contact depth-of-field camouflage sensing

Ionically conductive fibers have promising applications; however, complex processing techniques and poor stability limit their practicality. To overcome these challenges, we proposed a stress-induced adaptive phase transition strategy to conveniently fabricate self-encapsulated hydrogel-based ionically conductive fibers (se-HICFs). se-HICFs can be produced simply by directly stretching ionic hydrogels with ultra-stretchable networks (us-IHs) or by dip-drawing from molten us-IHs. During this process, stress facilitated the directional migration and evaporation of water molecules in us-IHs, causing a phase transition in the surface layer of ionic fibers to achieve self-encapsulation. The resulting sheath-core structure of se-HICFs enhanced mechanical strength and stability while endowing se-HICFs with powerful non-contact electrostatic induction capabilities. Mimicking nature, se-HICFs were woven into spider web structures and camouflaged in wild environments to achieve high spatiotemporal resolution 3D depth-of-field sensing for different moving media. This work opens up a convenient route to fabricate stable functionalized ionic fibers.

Implication of Freeze-Thaw Erosion and Mechanism Analysis of High-Performance Aromatic Liquid Crystal Fibers.

According to the demand for high-performance fibers for high-latitude ocean exploration and development, this paper selects representative products of high-performance liquid crystal fibers: thermotropic liquid crystal polymer fibers (TLCP) and poly p-phenylene terephthalamide (PPTA) fibers. Through a series of freeze-thaw (F-T) experiments for simulating a real, cold marine environment, we then measure the retention of mechanical properties of these two kinds of fibers. Before that, due to the difference in their chemical structures, we tested their Yang-Laplace contact angle (YLCA) and water absorption; the results suggested that PPTA fibers would absorb more moisture. Surprisingly, then, compared with thermotropic liquid crystal polymer (TLCP) fibers, the retention of the mechanical properties of poly p-phenylene terephthalamide (PPTA) fibers decreased by around 25% after the F-T experiments. The Fourier-transformed infrared (FT-IR) analysis, the attenuated total reflection (ATR) accessory analysis and the degree of crystal orientation measured by two-dimensional wide-angle X-ray diffraction (2D-WAXD) confirm that no changes in the chemical and the orientation structure of the crystal region of the fibers occurred after they underwent the F-T cycles. However, as observed by scanning electron microscopy (SEM), there are microcracks of various extents on the surface of the PPTA fibers, but they do not appear on the surface of TLCP fibers. It is obvious that these microcracks will lead to the loss of mechanical properties; we infer that the moisture absorbed by the PPTA fibers freezes below the freezing point, and the volume expansion of the ice causes the collapse of the microfibrillar structure. The two sorts of fibers subjected to the F-T experiments are immersed in a sodium chloride solution, and the amount of water infiltrated into the PPTA microfibrillar structure is evaluated according to the content of sodium ions in the fiber surface and subsurface layers through X-ray spectroscopy (EDS) elemental analysis. From the above analysis, we found that TLCP fibers can more effectively meet the operating standards of the severe and cold marine environment.

Recycled Carbon Fibers with Improved Physical Properties Recovered from CFRP by Nitric Acid

To effectively reuse a large amount of Carbon Fiber Reinforced Plastics (CFRP) waste, the carbon fibers should be able to be recovered without degrading their quality. In this report, we developed a new approach to recover carbon fibers from CFRPs with improved physical properties compared to virgin carbon fibers with an environmentally friendly recycling method using nitric acid. Following the decomposition of the CFRP waste in nitric acid at 80 °C, both recycled carbon fibers and decomposed resin were recovered. The obtained recycled carbon fibers showed 1.4 times higher tensile strength and 2.2 times higher interfacial shear strength to resin compared to virgin carbon fibers. TEM-EDX analysis showed a decrease in the abundance of voids existing in the carbon fiber surface layer and new polar functional groups caused by nitric acid existing inside the voids, leading to increased tensile strength. Furthermore, XPS analysis showed that the interfacial shear strength improved due to the formation of new polar functional groups due to nitric acid. The possibility of applying recycled carbon fibers to CFRP products was shown by elucidating the mechanism that expressed its physical properties during the recycling process, leading to a novel approach to realizing closed-loop recycling.

Synthesis and application of a novel high durable cotton flame retardant rich in P[sbnd]N covalent bonds and ammonium phosphate groups

In this paper, a novel high molecule and formaldehyde-free reactive flame retardant, ammonium salt of polyethyleneimine phosphamide phosphoric acid (APEIAPAP), was synthesized for cotton fabrics, and its structure was characterized by nuclear magnetism and Fourier transform infrared spectroscopy test (FTIR). In its molecule, there was a p-π conjugation in NP(O) group, resulting in the increase of the stability of NP(O) covalent bond and P(O)OC between the flame retardant and cotton fibers. The FTIR and X-ray photoelectric spectrometer results demonstrated that the APEIAPAP reagent was grafted on cellulose through P(O)OC covalent bond. The results obtained by the vertical flame test, limiting oxygen index (LOI) test, thermogravimetric analysis, thermogravimetric-Fourier infrared spectrometer measurement, and conical calorimetric test showed that the treated samples had outstanding flame retardancy and APEIAPAP performed condensed phase flame retardant mechanism. In addition, the LOI of 25 % APEIAPAP treated cotton fabric could reach 50.6 %, and remain at 37.9 %, even after 50 LCs according to the AATCC 61-2013 3A standard. The microscopic surface morphology showed that the APEIAPAP was mainly grafted on the surface layer of cotton fibers. The tensile strength and bending performance of the treated cotton samples were well sustained. These results demonstrated that introducing the P element into the flame retardant through P(O)N covalent bond, and increasing the flame-retardant molecule weight, were efficient to significantly increase the durability of the treated cotton fabric.

Graphene-coated alumina nano/microfibers as filler for composites

The present work is focused on the preparation and characterization of composite nano/microfibers based on alumina applicable as fillers in ceramic-matrix composites. The graphene-coated Al2O3 microfibers have been prepared in the form of continuous alumina/graphene fibers from electrospun precursors using needle-less electrospinning, calcination, and catalyst-free chemical vapor deposition of graphene layers on the surface of the microfibers. The phase composition and morphology of the composite fibers were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning, and transmission electron microscopy (SEM and TEM). The porosity of the final fibers was evaluated by low-temperature nitrogen adsorption. The surface microstructures of composite fibers were rough and their diameters were in the range from 300 nm to 2 μm. The phase transformation at 1100 °C led to the formation of a mixture of γ-, δ-, and α-Al2O3. TEM results confirmed that the alumina fibers were covered by the 3–4 layers of graphene-based structure. The specific surface area of pure alumina fibers after carbon deposition slightly increased from the initial 40 m2/g to 45 m2/g, due to a slightly wavy surface of graphene layers. Raman spectroscopy and XPS analysis results showed that the surface layer of fibers is formed as graphene oxide. Between the graphene oxide and alumina grains a chemical bonding C–O–Al, C–O–O–Al was discovered as the nucleation of the graphene oxide sheet. The growth mechanism of graphene oxide layers on the surface edges of Al2O3 grains was described.

Research on drilling CFRP laminate with a thin woven glass fiber surface layer using plane rake–faced twist drill

The delamination produced during drilling CFRP will affect its structural strength seriously. Delamination is closely related to the thrust force during drilling, which is closely related to the tool, so it is particularly important to choose the tools with appropriate geometric structure. Many scholars used tools with different geometric structure to drill CFRP, and then conducted the drilling damage analyses and drilling mechanism researches. It finally came to a conclusion that a drill with a special structure had certain advantages compared with a common twist drill in the drilling process. A new type of plane rake–faced twist drill was used to drill the CFRP laminate with a thin-woven glass fiber surface layer. Experimental results showed that the plane rake–faced twist drill along cutting edge had a constant reference rake angle value, which caused the plane rake–faced twist drill generated smaller thrust force and less drilling damage than the common twist drill. As the reference rake angle of the plane rake–faced twist drill increased, the thrust force and drilling damage decreased. It was revealed the inhibition of the thin-woven glass fiber surface layer on the drilling damage at entrance and exit. Finally, it was proposed that when the plane rake–faced twist drill was used to drill CFRP laminate with a thin-woven glass fiber surface, 46° reference rake angle should be selected.

Experimental study on improving the properties of rock wool and glass wool by silica aerogel

Besides thermal insulation performance, waterproofness and mechanical strength are also important indexes for evaluating thermal insulation materials. In this paper, silica aerogel/rock wool (SA/RW) composite plates and silica aerogel/glass wool (SA/GW) composite plates were prepared by infiltration and atmospheric pressure drying method. The influence of silica aerogel mass fraction and infiltration time on thermal conductivity, short-term water absorption and compressive strength of composite plates were explored, and the modification effects of SA/RW and SA/GW composite plate under the optimum ratio were analyzed. The changes in microstructure before and after modification were obtained by SEM. The results showed that the addition of silica aerogel significantly changed the surface layer of inorganic fibers, which can form a relatively stable composite system. When the mass fraction of silica aerogel reached 8% and the infiltration time was 20 min, the thermal conductivity of SA/RW and SA/GW composite plate was 0.0330 W/(m·k) and 0.0263 W/(m·k), which were 26.7% and 20.3% lower than those before modification, and the apparent density reached 177.55 kg/m3 and 53.61 kg/m3, respectively. The short-term water absorption was 0.78 kg/m3 and 0.65 kg/m3, which was 35% and 36.2% lower than that before modification. The compressive strength was 42.6 kPa and 14 kPa, respectively, increased by 7% and 103% compared with that before modification.

High-efficiency dispersant-free polyester dyeing using D5 non-aqueous medium

Conventional polyester dyeing with disperse dyes consumes a large amount of freshwater resource and requires a great deal of dispersant, which poses a major challenge to the dyeing and finishing industry. To meet the requirements of clean production and sustainable development, a modified decamethyl-cyclopentasiloxane (D5) non-aqueous medium dyeing system containing a little water was proposed in this study, and the effect and mechanism of a little water on the polyester dyeing were investigated. Both D5 and liquid paraffin non-aqueous medium dyeing systems containing approximately 50% (on weight of fabric, owf) water are observed to significantly improve the dye uptake of disperse dyes and the color strength of dyed fabric with excellent levelness and high colorfastness. The confocal laser scanning microscopy (CLSM) with fluorescent labeling technique confirms the accessibility of water in the surface layer of polyester fiber, and the dynamic thermomechanical analysis (DTMA) reveals the diffusion of water into the polyester fiber, thereby reducing the glass transition temperature (Tg) of polyester fibers by plasticization effect, promoting the movement of fiber molecular chain segments, and enabling the fixation stage of dyeing to be performed at a lower temperature. The dyeing principle of the modified D5 medium dyeing of polyester has enriched the theoretical system of non-aqueous medium dyeing, being conducive to facilitate the development of the sustainable dispersant-free and water saving polyester dyeing technology.

Structural Morphology of Rabbit Patella and Suprapatella Cartilage by Microscopic MRI and Polarized Light Microscopy.

In order to appreciate the roles articular cartilage of sesamoid bones and sesamoid fibrocartilage play in anatomy and pathology, the articular cartilage of the patella (n = 4) and suprapatella (n = 4) (a sesamoid fibrocartilage) of 12 to 14 weeks old New Zealand rabbits were studied qualitatively and quantitatively. The intact knee joints and block specimens from the joints were imaged using microscopic magnetic resonance imaging (µMRI) at a 97.6-µm pixel resolution for the former and 19.5-µm resolution for the latter. Histological sections were made out of the µMRI-imaged specimens, which were imaged using polarized light microscopy (PLM) at 0.25-, 1-, and 4-µm pixel resolutions. The patella cartilage varied in thickness across the medial to lateral ends of the sesamoid bone with the central medial aspect slightly thicker than the lateral aspect. The suprapatella fibrocartilage decreased proximally away from the knee joint. Quantitative results of patellar cartilage showed strong dependence of fiber orientation with the tissue depth. Three histological zones can be clearly observed, which are similar to articular cartilage from other large animals. The sesamoid fibrocartilage has one thin surface layer (10 µm thick) of parallel-arranged structured fibers followed immediately by the majority of random fibers in bulk tissue. T2 relaxation time anisotropy was observed in the patellar cartilage but not in the bulk fibrocartilage. Given the different functions of these 2 different types of cartilages in joint motion, these quantitative results will be beneficial to future studies of joint diseases using rabbits as the animal model.

Effect of carbon fiber nanostructure on surface morphology under high-fluence ion irradiation

The results of experimental study of the surface nano-and microstructuring of polyacrilonitrile (PAN) based carbon fiber VMN-4 and viscose based carbon cloth TGN-2MK under 30 keV Ar+ irradiation are presented. Scanning electron microscopy shows a strong difference in evolution of ion-induced morphology for these two carbon fiber types. At sufficiently high fluences, a corrugated morphology is formed on the PAN based carbon fiber, while a network of nanowalls is formed on the viscose based carbon fiber. The found differences are associated with a significant effect of the structure of the surface layer of carbon fiber on ion-induced dimensional changes.

Efficient preparation of chemically crosslinked recyclable photodeformable azobenzene polymer fibers with high processability and reconstruction ability via a facile post-crosslinking method

Chemically crosslinked recyclable photodeformable azobenzene (azo) polymer actuators with good stability (toward organic solvents and higher temperatures) and high processability and reconstruction ability hold great promise in many applications, but their development remains a challenging task. Herein, we report on for the first time a facile and highly efficient post-crosslinking method for addressing this issue. It involves first the synthesis of side-chain polymers bearing N-hydroxysuccinimide (NHS) carboxylate-substituted azo mesogens, fabrication of uniaxially oriented fibers from these azo polymers by the simple melt spinning method, and their subsequent post-crosslinking with cystamine (a diamine containing a disulfide bond) under mild conditions. The resulting chemically crosslinked fibers not only showed rapid and reversible photoinduced bending and unbending at ambient temperature as well as high mechanical strength and good solvent/heating stability, but also could be easily recycled into processable azo polymers in the presence of a reducing agent that can cleave the disulfide bond into thiol groups (i.e., tributylphosphine). In particular, the occurrence of the post-crosslinking reaction only on the thin surface layers of the azo polymer fibers afforded recycled polymers with large amounts of NHS carboxylate-substituted azo mesogens (together with a small amount of oxygen/heating-sensitive thiol-substituted ones) in the first several (at least 5) recycling processes, thus allowing highly efficient reconstruction of photodeformable fibers with excellent photomobile properties by applying melt spinning and post-crosslinking (by using cystamine) methods. The strategy presented here opens the new possibility to the facile and efficient development of various advanced chemically crosslinked recyclable photodriven actuators.

TiO2/gold-graphene hybrid solid core SPR based PCF RI sensor for sensitivity enhancement

We propose a d-shaped photonic crystal fiber (PCF) refractive index (RI) sensor based on surface plasmon resonance (SPR), capable to work in both visible and near-infrared (NIR) wavelength (410–1790 nm) region. Gold (Au) is deposited on the flat outer surface of the PCF to excite the plasmons. A thin titanium dioxide (TiO2) layer is sandwiched between fiber surface and gold layer so that the gold nanoparticles can strongly attach with the fiber surface. It also helps to shift the resonance wavelength of the proposed sensor to near IR region which is much advantageous for biosensing. A thin graphene layer is applied on Au to assist adsorption of ample biomolecules on its surface. It also prevents gold from oxidation. Simulation results show the theoretical maximum wavelength sensitivity of 48,900 nm/RIU and average sensitivity of 13112.5 nm/RIU in the RI rage of 1.32−1.40. Besides this, the proposed sensor shows the higher amplitude sensitivity of 738.74/RIU with high resolution and maximum figure of merit (FOM) of 7.604×10-6RIU and 611.25/RIU, respectively. These promising outcomes of the proposed sensor make itself to be a potential candidate for the various analyte (organic chemicals, biomolecules) detection. Moreover, the fabrication feasibility of our proposed D-shaped sensor becomes easier than the circular PCF sensors as it avoids the internal coating of the plasmonic metals.

Influence of stack sequence on the mechanical characteristics of hybrid composites analyzed using cone beam computed tomography and scanning electron microscopy

AbstractThe hybridization of composites has recently seen an exponential growth in acceptance due to its ability to improve the property such as toughness of composites. Hybridization of fibers is known to give a better balance of properties and increases the opportunity to use natural fibers, thereby reducing the impact on the environment without compromising utility. This study deals with hybridization of ultrahigh‐molecular‐weight polyethylene (UHMWPE) with natural fibers such as flax and jute using phenol formaldehyde as the resin. Composite panels of 4 mm thickness, comprising of eight layers were fabricated in six different fiber stack sequences using hand lay‐up and compression molding techniques. The effect of stack sequence on the composites' flexural, interlaminar shear, and impact properties were investigated using scanning electron microscopy and cone beam computed tomography techniques. Composites with outer UHMWPE fibers and having flax fibers as inner core were found to have superior flexural and interlaminar shear properties of 44.45 and 5.52 MPa, respectively. Also composites with surface layers of flax fibers displayed maximum impact strength of 91.08 kJ/m2. The results indicate that the stack sequence has a significant influence on the properties of the composite under flexural and impact loading.

Thermal influence on surface layer of carbon fiber reinforced plastic (CFRP) in grinding

In this study, we investigated thermal influence on surface layer of CFRP in grinding with heat conduction analysis using grinding temperature at wheel contact area on dry and wet condition. Moreover, the thermal affected layer was analyzed through an experiment to examine the temperature of glass transition and thermal decomposition of the matrix resin that composes the CFRP used in this study. The influence of thermal effect on grinding of CFRP was verified based on observation of ground surface finish after grinding using SEM and the measurement of surface roughness. From the measurement result of DSC (Differential Scanning Calorimetry)，TG-DTA (Thermogravimetry-Differential Thermal Analysis), It was found that the thermal affected layer of CFRP includes a layer in which the matrix resin is changed in quality by exceeding the glass transition temperature and a layer in which the matrix resin is thermally decomposed by exceeding the thermal decomposition temperature. In addition, it was found that the surface roughness was significantly reduced if the thermal affected layer with thermal decomposition was generated. In each grinding atmosphere, it tended to increase of grinding temperature at wheel contact area with increasing in the setting depth of cut. In the case of dry grinding, grinding temperature at wheel contact area increased up to t thermal decomposition temperature of the matrix resin. However, in the case of the wet grinding, grinding temperature at wheel contact area did not increase until thermally decomposition temperature. From the result of simulation about thermal affected layer, influence of grinding heat increased with increasing in the setting depth of cut. Ultimately, the thermal affected layer with thermal decomposition was generated in dry grinding. Moreover, from the results of SEM observation, it was confirmed that the surface finish properties deteriorated significantly due to thermal decomposition of the matrix resin in the case of Δ = 400 μm in the setting depth of cut at fiber angle θ = 0°. On the other hand, it was confirmed that the micro damage of carbon fiber was occurred in wet grinding at each setting depth of cut.

In-situ generated gold nanorods on surface layer of fibers: facile preparation and unprecedented high catalytic activities in reduction of 4-nitrophenol

Unlike the versatile and facile preparation techniques for Au nanospheres (Au NSs), the synthetic methods for the one-dimensional anisotropic Au nanorods (Au NRs) were limited and relatively complicated, which restricted their practical applications. Hence, facile preparation methods using conventional raw chemicals are highly desirable for Au NRs. In this contribution, we developed a new facilely-prepared polymer template and stabilizer, i.e. hyperbranched polyethylenimine (PEI) modified polyacrylonitrile (PAN) fiber (abbreviated as PAN-g-PEI), for the in-situ generation of Au NRs through one-step NaBH4 reduction of the complex of PAN-g-PEI0.06 and HAuCl4 in water. Only PAN-g-PEI0.06 having a low PEI grafting amount was an effective polymer template and stabilizer. Under the same preparation condition, the utilization of other PAN-g-PEI with higher PEI grafting amount only resulted in Au NSs, not Au NRs. Au NRs/PAN-g-PEI0.06 was excellent recyclable catalyst for NaBH4-reduced reaction of 4-nitrophenol. Its turnover frequency was ca. 63.5 min−1, higher than not only Au NSs supported by PAN-g-PEI, but also majority of nanostructured metal catalytic systems. Moreover, Au NRs/PAN-g-PEI0.06 exhibited an unprecedentedly immortal catalytic activity, superior to Au NSs supported by PAN-g-PEI with higher PEI grafting amount. The easy preparation, recyclable nature and immortal catalytic activity make Au NRs/PAN-g-PEI0.06 a very promising material for practical use.

Localized Surface Plasmon Resonance Based Hetero-Core Optical Fiber Sensor Structure for the Detection of L-Cysteine

In this article, a hetero-core optical fiber sensor structure is developed for the diagnosis of L-Cysteine content in human urine. The hetero-core structure is created by sequentially cascading the single mode-multimode-single mode fibers using thermal fusion splicing. The multimode section of fiber probe is etched out and coated with synthesized gold nanoparticles (AuNPs), polyvinyl alcohol stabilized silver nanoparticles (PVA-AgNPs) and graphene oxide (GO). The AuNPs and PVA-AgNPs are used to initiate the localized surface plasmon resonance (LSPR) phenomenon on the application of exponentially decaying evanescent waves. The layer of GO is used to provide the larger surface area and binding sites for the L-Cysteine (L-Cys) molecules. Based on the combination of NPs, two different configurations of sensor probes are developed. In first one, a layer of AuNPs is deposited over fiber surface and further followed by the coating of GO, and named Probe I. In the second one, a layer of PVA-AgNPs is sandwiched between the fiber surface and GO layer and termed as Probe II. The characterization of synthesized NPs and GO solutions, and developed sensor probes are done by using UV-Vis spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). To authenticate the biocompatibility of developed sensor probes, the artificial aqueous samples of L-Cys ranges from 0 μM to 1 mM are tested. To determine the stability of L-Cys, a pH level based study is also carried out to ensure the good stability of analyte in aqueous samples. From the results, it was ascertained that the response of Probe II is better in terms of attained limit of detection and sensitivity that is 126.6 μM and 0.0009 nm/μM, respectively.

Highly Sensitive and Stretchable Polyurethane Fiber Strain Sensors with Embedded Silver Nanowires.

Flexible strain sensors have attracted a great amount of attention for promising applications in next-generation artificially intelligent devices. However, it is difficult for conventional planar strain sensors to meet the requirements of miniature size and light weight for flexible electronics. Herein, a highly sensitive and stretchable fiber strain sensor with a millimeter diameter was innovatively fabricated by the capillary tube method to integrate silver nanowires (AgNWs) in polyurethane (PU) fibers. Scanning electron microscopy results demonstrate that AgNWs were embedded into the surface layer of PU fibers and formed completely conductive networks. The unique AgNW networks endow the PU/AgNW fibers with superior electrical conductivity of 3.1 S/cm, high elongation at break of 265%, wide response range of 43%, high gauge factor of 87.6 up to 22% strain, fast response time of 49 ms, and excellent reliability and stability. Such satisfactory stretchability and sensitivity is attributed to the combination of the highly stretchable PU matrix and the embedded architecture of the AgNW conductive network. Moreover, PU/AgNW fibers can be employed as wearable devices to detect various human motions and to drive light-emitting diodes at a lower voltage (2.7 V).

Studies on the influence of surface treatment type, in the effectiveness of structural adhesive bonding, for carbon fiber reinforced composites

Primary intent of the present paper is to correlate the effectiveness of surface preparation type (pre-bonding), such as solvent cleaning, sanding (mechanical abrade), chemical etching (alkaline and acid), and peeling of sacrificial surface layer (peel ply) of carbon fiber reinforced composite (CFRC) test specimens, with the corresponding effect to the final strength of adhesive bonding. The analysis was performed by means of several spectroscopic and microscopic techniques, such as XPS, SEM, AFM, and a contact angle measurement technique which provides a direct, fast and easy measurement of the surface energy of the fiber composites. The adhesively bonded carbon fiber composites based on the different surface treatments were mechanically tested by employing the ASTM D 5528-0 (reapproved 2007) standard. The double cantilever beam (DCB) specimen geometry was used to evaluate the value known as opening Mode I inter-laminar fracture toughness (GIC) in adhesive bonds of carbon fiber composite materials. The results were varying between 1 and 1.8 kJ/m2 for GIC analysis and around 50 mm for delamination lengths. The mechanics of the linear elastic fracture is considered a tool for the failure of the laminate in composite materials with cracks or cuts in the plane, due to the presence of damaged zones in the tip of the crack; which is therefore applied to the study of delamination or fracture toughness.

Nano‐modified HDPE/PA6 microfibrillar composites: Effect of aminated graphite platelets coupling

ABSTRACTModification of microfibrillar composites (MFCs) by nanofillers shows important effects of its localization on performance. This work deals with control of migration/localization of amine‐modified graphite nanoplatelets (GNPAs) in the HDPE/PA6 system through their in situ coupling. GNPA/HDPE linking also leads to complex morphology of PA6 fibers. Although such control of GNPA localization and migration in MFC is limited, marked variations of properties, including decrease with high draw ratio, occurs. This is in spite of the fact that structure and crystallinity are comparable with that of the polymer/GNPA adduct. The reason is a more pronounced negative effect of presence of the GNP adducts in the fiber surface layer on HDPE crystallinity, in comparison with neat GNP, that is, formation of “soft” interface. The negative effects were markedly eliminated by pre‐blending and coupling of GNPA in both polymer phases. Results confirm more effective control of MFC performance by in situ coupling of GNPA with polymer components in comparison with a nonreactive system. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47660.