Interfacial Adhesion Of Composites Research Articles

Bioactive chitosan/polydopamine nanospheres coating on carbon fiber towards strengthening epoxy composites

This paper initially examines the feasibility and effectiveness on interfacial adhesion of composites when grafting nanoparticle-structured polydopamine (PDA) and chitosan around carbon fiber periphery. The resulting interfacial shear strength was maximized as 92.3 MPa, delivering 50.1 % and 15.7–16.2 % gains over those of control fiber and only polydopamine nanospheres (PDANPs) or only chitosan modified fiber composites. Measuring surface morphology and thermal stability of fibers found that abundant PDANPs well adhered with the help of chitosan, highlighting nanoscale size effects and intrinsic adhesiveness of PDA. Under good wettability, rich and dense interfacial interactions (covalent and hydrogen bond, electrostatic interaction, and π conjugation) caused by PDANPs/chitosan coating provides impetus for effective stress transfer. Additionally, the stable “soft-rigid” combination of chitosan and PDANPs adds the efficiency of crack passivation. As such, it is hoped that this work could fully explore the possibility of PDA geometry in interphase engineering of fiber composites.

Carbon fiber in situ grown ZIF‐67 nanocrystals with excellent electrochemical and interfacial property

AbstractCarbon fiber(CF) reinforced flexible composites had a wide range of applications. However, the interfacial adhesion of composites was weak as a result of the smooth and chemically inert CF surface. To settle this issue, this paper described a method to enhance the specific surface area, roughness and wettability of the CF surface by in situ growing Cobalt‐based zeolitic imidazolate framework (ZIF‐67) nanocrystals and CF reinforced waterborne polyurethane (WPU) composites were prepared by a simple casting method. Scanning electron microscopy clearly revealed uniformly grown ZIF‐67 nanoarrays with distinct morphology on the CF surface. As a result, the CF@ZIF‐3 electrode exhibited excellent electrochemical property, with specific capacitance reaching 368.2 mF/cm2. The reinforcing effect of ZIF‐67 with different morphology was further verified through transverse fiber bundle tension test and shear bonding strength measurements, showing improvements of 51.9 and 72.1% respectively, in comparison to the CF/WPU composites due to the unique structure of the ZIF‐67 nanocrystals acted as buffer area, effectively relieving stress concentration and altering the direction of crack propagation. As a result, the interfacial properties of the composites were enhanced. Moreover, tensile and tear strengths of CF@ZIF/WPU composites showed remarkable improvement compared to CF/WPU composites. This study presented a potential reinforcement strategy for achieving high‐performance CF/WPU composites.Highlights ZIF‐67 with different morphologies were grown in situ on the CF surface. CF@ZIF electrode exhibited excellent electrochemical property. ZIF‐67 interface layer improved interfacial properties of composites. The tensile strength of the composites improved after ZIF‐67 modification. Introduction of ZIF‐67 enhanced the tear strength of composites.

Improving mechanical and thermal properties of short carbon fiber/polyamide 6 composites through a polydopamine/nano‐silica interface layer

AbstractCarbon fiber (CF) reinforced matrix composites have been applied widely, however, the interfacial adhesion of composites is weak due to smooth and chemically inert of CF surface. To solve this problem, A polydopamine/nano‐silica (PDA‐SiO2) interfacial layer on carbon fiber surface was constructed via polydopamine and nano‐ SiO2 (CF‐PDA‐SiO2) by a facile and effective method to reinforce polyamide 6 composites (CFs/PA6). The effects of PDA‐SiO2 interfacial layer on crystallization structure and behavior, thermal properties, and mechanical properties of CFs/PA6 composites were investigated. Furthermore, interfacial reinforcement mechanism of composites has been discussed. This interfacial layer greatly increased the number of active groups of CF surface and its wettability obviously. The tensile strength of CF‐PDA‐SiO2/PA6 composites increased by 28.09%, 19.37%, and 26.22% compared to untreated‐CF/PA6, CF‐PDA/PA6, and CF‐SiO2/PA6 composites, respectively, which might be caused by the increased interfacial adhesion between CF and PA6 matrix. The thermal stability, crystallization temperature, crystallinity, and glass transition temperature (Tg) of CF‐PDA‐SiO2/PA6 composites improved correspondingly, attributing to the heterogeneous nucleation of nano‐SiO2 in the crystalline area and hydrogen bonds with molecular chains of PA6 in the amorphous area. This work provides a novel strategy for the construction of interfaces suitable for advanced CF composites with different structures.

2D graphene oxide and MXene nanosheets at carbon fiber surfaces

Carbon fibers, which are known for their high strength to weight ratio and thermal and chemical stability, are key components in advanced structural composites. Controlling the fiber-matrix interface is key to achieving required physical performance. Functional two-dimensional (2D) materials that can conformally coat the fiber surface facilitate interface and interphase engineering for enhanced mechanical properties and added functionalities. Understanding how 2D flakes bond, integrate, and perform at carbon fiber interfaces is key to developing multifunctional high-strength composites. In this study, we focus on the surface interactions of graphene oxide (GO) and Ti3C2Tx MXene nanoflakes at the surface of low-tension carbon fibers with and without amine functionalization by in-depth multimode scanning probe microscopy. We suggest that beyond strengthening the interfaces, GO and MXene provide efficient charge transfer with MXene also adding conductivity to the fiber surface, extending potential applications of composites to broad areas including structural supercapacitors and battery cooling/packaging materials. GO and MXene modified fibers not only create opportunities for increased interfacial adhesion in composites via increased surface roughness, but also act as anchors for bonding, energy dissipation, charge transport, and local interface stiffening.

Mater-Bi/Brewers' Spent Grain Biocomposites-Novel Approach to Plant-Based Waste Filler Treatment by Highly Efficient Thermomechanical and Chemical Methods.

Thermoplastic starch (TPS) is a homogenous material prepared from native starch and water or other plasticizers subjected to mixing at a temperature exceeding starch gelatinization temperature. It shows major drawbacks like high moisture sensitivity, poor mechanical properties, and thermal stability. To overcome these drawbacks without significant cost increase, TPS could be blended with bio-based or biodegradable polymers and filled with plant-based fillers, beneficially waste-based, like brewers’ spent grain (BSG), the main brewing by-product. Filler modifications are often required to enhance the compatibility of such composites. Herein, we investigated the impact of BSG thermomechanical and chemical treatments on the structure, physical, thermal, and rheological performance of Mater-Bi-based composites. Thermomechanical modifications enhanced matrix thermal stability under oxidative conditions delaying degradation onset by 33 °C. Moreover, BSG enhanced the crystallization of the polybutylene adipate terephthalate (PBAT) fraction of Mater-Bi, potentially improving mechanical properties and shortening processing time. BSG chemical treatment with isophorone diisocyanate improved the processing properties of the composites, expressed by a 33% rise in melt flow index. Depending on the waste filler’s selected treatment, processing, and rheological performance, thermal stability or interfacial adhesion of composites could be enhanced. Moreover, the appearance of the final materials could be adjusted by filler selection.

Dopamine concentration-dependent surface modification for gaining carbon fiber composites with enhanced interfacial adhesion

Self-assembly process of dopamine concentration-dependent polydopamine (PDA) on graphitized carbon fiber is elucidated, as well as its effects on interfacial adhesion of composites. With the increase of dopamine concentration, active PDA nanospheres in Tris-solution first adhere to fiber surface to form a thin film, then accompanies with the creation of ever-increasing PDA aggregates instead of continuing to form a thicker PDA film. The optimal dopamine additive amount is 0.3 g for 52.6% IFSS improvement by analogy to untreated fiber, because of the greatly enhanced epoxy wettability from the contribution of the synergistic actions of more polar groups and rougher surface. Less and higher dopamine additions go against substantial increment in IFSS, especially for higher ones that large-sized PDA nanospheres are apt to induce stress concentration, sacrificing the contribution by more active groups.

Enhanced interfacial adhesion of carbon fiber/epoxy composites by synergistic reinforcement with multiscale “rigid-flexible” structure at interphase

Carbon fiber (CF) reinforced matrix composites have wide application prospect, however, the interfacial adhesion of composites is weak due to smooth and chemically inert of CF surface. To settle this problem, two kinds of synergistic hierarchical reinforcements with multiscale “rigid-flexible” structures [CF-graphene oxide (GO)-carbon nanotubes (CNTs)- polyamide (PA) and CF-CNTs-GO-PA] were fabricated through simple esterification and anionic polymerization reactions. The effects of the interface thickness and grafting sequence on the interfacial properties of the composites were explored. The interfacial shear strength (IFSS) of the CF-GO-CNTs-PA/resin composites was 88.3 MPa, which exceeded those of CF, CF-GO-CNTs, CF-GO-PA, and CF-CNTs-GO-PA by 80.9%, 11.5%, 2.3%, and 1.4%, respectively. This was mainly ascribed to the thicker gradient interface layer , the synergistic effects of GO and CNTs, the rigid and flexible structure, as well as the interfacial interactions and mechanical interlocking effect in the CF-GO-CNTs-PA/resin composite. This work provides a novel concept for the construction of interfaces suitable for advanced CF composites with different structures.

Hybrid biocomposites from polypropylene, sustainable biocarbon and graphene nanoplatelets

Polypropylene (PP) is an attractive polymer for use in automotive parts due to its ease of processing, hydrophobic nature, chemical resistance and low density. The global shift towards eliminating non-renewable resource consumption has promoted research of sustainable biocarbon (BioC) filler in a PP matrix, but this material often leads to reduction in composite strength and requires additional fillers. Graphene nano-platelets (GnPs) have been the subject of considerable research as a nanofiller due to their strength, while maleic anhydride grafted polypropylene (MA-g-PP) is a commonly used compatibilizer for improvement of interfacial adhesion in composites. This study compared the thermo-mechanical properties of PP/BioC/MA-g-PP/GnP composites with varying wt.% of GnP. Morphological analysis revealed uniform dispersion of BioC, while significant agglomeration of GnPs limited their even dispersion throughout the PP matrix. In the optimal blend of 3 wt.% GnP and 17 wt.% BioC biocontent, tensile strength and modulus increased by ~19% and ~22% respectively, as compared to 20 wt.% BioC biocomposites. Thermal stability and performance enhancement occurred through incorporation of the fillers. Thus, hybridization of fillers in the compatibilized matrix presents a promising route to the enhancement of material properties, while reducing petroleum-based products through use of sustainable BioC filler in composite structures.

Cu (II) coordination modification of aramid fiber and effect on interfacial adhesion of composites

In this article, active groups were introduced to the surface of aramid fiber by building a Cu2+ bridge between the aramid fiber and polyethyleneimine (PEI) to improve adhesion in composites between the aramid fiber and the matrix such as epoxy resin. The changes in the structure and properties of the aramid fiber were verified with Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and the single-fiber pull-out test. The FTIR and XPS results show a significant change in the structure and morphology of the aramid fiber after modification. The results of the single-fiber pull-out test show that the interfacial shear strength (IFSS) of epoxy composites reinforced with PEI-grafted aramid fiber increases by 48.8% compared with the IFSS of epoxy composites reinforced with untreated fiber. Thus, the proposed method can improve the interfacial bonding of composites by creating a copper ion bridge between the aramid fiber and PEI.

Improvement of aramid fiber III reinforced bismaleimide composite interfacial adhesion by oxygen plasma treatment

Domestic Aramid Fiber III (DAF III) was modified by oxygen plasma treatment. The effects of oxygen plasma treatment power on fiber surface and DAF III reinforced bismaleimides (BMI) composite interfacial properties were investigated, respectively. The fiber surface characteristics were analyzed by X-ray photoelectron spectroscopy, Scanning Electron Microscopy, Atomic Force Microscopy and Dynamic Contact Angles Analysis, respectively. The results showed that oxygen plasma treatment introduced new oxygen containing groups such as C=O and –COO on to the fiber surfaces, changed the fiber surface morphologies and enhanced surface roughness by oxidative reactions and plasma etching. Finally, the fiber surface wettability was effectively improved. The total free energy increased from 49.8 to 71.7 mJ/m2 at maximum with 300 W oxygen plasma treatment. The composite interlaminar shear strength (ILSS) was evaluated by short beam shear measurement. The ILSS value increased from 49.3 to 59.8 MPa (by 21.3%) within 300 W plasma treatment.

Protein-mediated interfacial adhesion in composites of cellulose nanofibrils and polylactide: Enhanced toughness towards material development

The role of animal protein, casein, as compatibilizer and eco-friendly dispersant in composites comprising cellulose nanofibrils (CNF) and polylactic acid (PLA) was investigated. The effect of casein-mediated surface modification of PLA was validated with dynamic adhesion experiments that considered the contact area according to JKR approximation. In fact, a remarkable increase by ∼50% in the work of adhesion between CNF and PLA was observed after casein adsorption. It is likely that the improved adhesion gave rise to an enhanced dispersion of CNF and PLA within the composite matrix. Moreover, the mechanical properties of the respective nanocomposites were significantly improved. When compared to protein-free CNF/PLA nanocomposites, the systems containing casein indicated an enhanced extensibility (by 130%) and tensile toughness (by 60%) whereas tensile strength and Young's modulus were improved to a limited extent (6 and 12%, respectively). Finally, it is demonstrated that the surface modification of PLA with casein improves the compatibility between CNF and PLA, which is a prerequisite for the feasible preparation of 3D shaped cellulose-based packaging materials by direct thermoforming.

Highly improved Uv resistance and composite interfacial properties of aramid fiber via iron (III) coordination

The poor Uv stability and weak interfacial adhesion are considered as the bottleneck problems for further application of aramid fiber. Herein, a new strategy, Fe3+ coordination, was reported for aramid fiber to simultaneous improve its Uv resistance and composite interfacial shear strength. Fe3+ was introduced onto aramid fiber by coordinating with benzimidazole unit of fiber structure. It can reach a doping capacity of as high as 1516ug/g fiber, and the fiber surface is saturatedly covered with Fe3+. The chemical structure of Fe3+-benzimidazole brings about strong metal-enhanced fluorescence emission effect, which, in turn, greatly raises its Uv stability. Owing to the Fe3+ coordination, the tensile strength of Fe-coordinated fiber could preserve as high as 96% after Uv irradiation, compared with 73% of untreated fiber. Meanwhile, the introduction of Fe3+ improves the surface polarity of aramid fiber and consequently leads to the increase of the composite interfacial shear strength by 39%. It is believed that the Fe-coordinated fiber integrates the advantages of easy production, cost-effective and increased Uv stability, as well as high composite interfacial adhesion, and can be used as promising enhancement for the advanced composite material in harsh environment.

Improved adhesion performances of aramid fibers with vinyl epoxy via supercritical carbon dioxide modification

In this paper, aramid fibers were treated under supercritical carbon dioxide (SCCO2) with isocyanate terminated liquid nitrile rubber to improve the adhesion performances of vinyl epoxy composites. The interfacial shear strength (IFSS) of vinyl epoxy composites was investigated by micro-bond test. The results indicate that the surface modification of aramid fibers in SCCO2 was an efficient method to increase the adhesion performances between fibers and vinyl epoxy. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were adopted to investigate the surface structure and composition of aramid fibers. The flexural strength and interlaminar shear strength (ILSS) of treated aramid fibers/vinyl epoxy composites was improved by 18.1% and 28.9% compared with untreated aramid fibers, respectively. Furthermore, the fractured surfaces of the composites were observed by SEM, which showed that the interfacial adhesion of composites has been remarkably changed.

Aging behavior of dielectric barrier discharge‐modified Twaron fibers in different storage environments

The aging behavior of air dielectric barrier discharge plasma treatment was investigated by storing the treated fibers respectively in air and in the oxidizing environment. Based on several testing methods, this study led us to the conclusion that the aging effects in the oxidizing environment were less obvious than that in air. X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy indicated that the decay of fiber surface polar groups was more remarkable for fibers aged in air. The atomic force microscopy photos showed that the further oxidation generated by the oxidizing chemicals such as ozone increased fiber surface roughness. Thus, there was no obvious reduction in the wettability of the modified fibers during the aging process in the oxidizing environment. These changes in surface properties could explain the variation in interlaminar shear strength of Twaron fiber reinforced composites. After the fibers were aged in air for 48 h, interlaminar shear strength of the composites declined by 18.4% while had a decrease of only 11.4% after aging for 48 h in the case of the oxidizing environment. The results were supported by the water absorption test, which also reflected the effects of different storage conditions on the composite interfacial adhesion, and showed the inhibitory effect of the oxidizing environment on plasma aging. Copyright © 2016 John Wiley & Sons, Ltd.

Surface modification of polyimide fibers by oxygen plasma treatment and interfacial adhesion behavior of a polyimide fiber/epoxy composite

AbstractOxygen plasma was used to enhance the surface behavior of polyimide (PI) fibers and PI fiber-reinforced epoxy composites were prepared in our present work. The effects of plasma treating times on the surface properties of PI fiber and the interfacial adhesion of PI fiber/epoxy composites were investigated. Surface chemical composition, surface morphologies and surface free energy of the fibers were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy and dynamic contact angle analysis, respectively. The results suggest that some oxygen functional groups were introduced onto PI fiber surfaces, and the surface roughness of fibers was enhanced. Resultantly, the surface free energy of fibers and the interfacial adhesion of composites were improved by the oxygen plasma treatment. The interlaminar shear strength of the composites increased to 70 MPa when the fibers were treated for 10 min, which proved good interfacial adhesion properties.

High performance natural rubber composites with a hierarchical reinforcement structure of carbon nanotube modified natural fibers

A simple and facile method for depositing multiwall carbon nanotubes (MWCNTs) onto the surface of naturally occurring short jute fibers (JFs) is reported. Hierarchical multi-scale structures were formed with CNT-networks uniformly distributed and fully covering the JFs (JF–CNT), as depicted by the scanning electron microscopy (SEM) micrographs. The impact of these hybrid fillers on the mechanical properties of a natural rubber (NR) matrix was systematically investigated. Pristine JFs were cut initially to an average length of 2.0 mm and exposed to an alkali treatment (a-JFs) to remove impurities existing in the raw jute. MWCNTs were treated under mild acidic conditions to generate carboxylic acid moieties. Afterward, MWCNTs were dispersed in an aqueous media and short a-JFs were allowed to react with them. Raman spectroscopy confirmed the chemical interaction between CNTs and JFs. The JF–CNT exposed quite hydrophobic behavior as revealed by the water contact angle measurements, improving the wettability of the non-polar NR. Consequently, the composite interfacial adhesion strength was significantly enhanced while a micro-scale “mechanical interlocking” mechanism was observed from the interphase-section transmission electron microscopy (TEM) images. SEM analysis of the composite fracture surfaces demonstrated the interfacial strength of NR/a-JF and NR/JF–CNT composites, at different fiber loadings. It can be presumed that the CNT-coating effectively compatibillized the composite structure acting as a macromolecular coupling agent. A detailed analysis of stress-strain and dynamic mechanical spectra confirmed the high mechanical performance of the hierarchical composites, consisting mainly of materials arising from natural resources.

Surface Characteristics of Single Sisal Fiber and Interfacial Adhesion of Composites

Surface characteristics including surface morphology and chemical composition of single sisal fiber and their influences on the interfacial adhesion of sisal fiber/phenolic resin composites were investigated by SEM, AFM, and XPS. The results showed that the surface of the untreated single sisal fiber contained a large amount of lignin (up to 51%). Chlorine dioxide treatment could reduce the surface lignin to a low content (20%). Removal of lignin from fiber surface could enhance the interfacial strength of sisal fiber/phenolic resin composites, giving rise to an increase by 36% in tensile strength. These results indicate that the surface properties of single sisal fiber can be tailored to improve the fiber/resin interfacial adhesion.

Novel high‐performance wave‐transparent aluminum phosphate/cyanate ester composites

AbstractAdvanced wave‐transparent composites are the key materials for many cutting‐edge industries including aviation and aerospace, which should have outstanding heat resistance, low dielectric constant and loss as well as good mechanical properties. A novel kind of high‐performance wave‐transparent composites based on surface‐modified aluminum phosphate AlPO4(KH‐550) and cyanate ester (CE) was first developed. The dielectric and dynamic mechanical properties of AlPO4(KH‐550)/CE composites were investigated intensively. Results show that AlPO4(KH‐550)/CE composites have decreased dielectric loss and higher storage moduli than pure CE resin; in addition, the composites with suitable AlPO4(KH‐550) concentration remain the outstanding thermal property and low dielectric constant of pure CE resin. The reasons attributing to these results are discussed from the effects of AlPO4(KH‐550) on the key aspects such as morphology, curing mechanism, and interfacial adhesion of composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Surface modification of armos fibers with oxygen plasma treatment for improving interfacial adhesion with poly(phthalazinone ether sulfone ketone) resin

AbstractWe introduce in this article oxygen plasma treatment as a convenient and effective method for the surface modification of Armos fibers. The effects of oxygen‐plasma‐treatment power on both the Armos fiber surface properties and Armos‐fiber‐reinforced poly(phthalazinone ether sulfone ketone) composite interfacial adhesion were investigated. The Armos fiber surface chemical composition, surface morphology and roughness, and surface wettability as a function of oxygen‐plasma‐treatment power were measured by X‐ray photoelectron spectroscopy, scanning electronic microscopy, atomic force microscopy, and dynamic contact angle analysis. The results show that oxygen plasma treatment introduced a lot of reactive functional groups onto the fiber surface, changed the surface morphology, increased the surface roughness, and enhanced the surface wettability. Additionally, the effect of the oxygen‐plasma‐treatment power on the composite interfacial adhesion was measured by interlaminar shear strength with a short‐beam bending test. Oxygen plasma treatment was an effective method for improving the composite interfacial properties by both chemical bonding and physical effects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Quantitative determination of interfacial adhesion in composites with strong bonding

An approach was proposed for the quantitative determination of adhesion strength in composites, in which adhesion is created by other mechanisms than secondary interactions. The approach is based upon a model, which gives debonding stress as a function of interfacial adhesion. Debonding stress was determined by acoustic emission experiments. The mechanism of deformation was checked by SEM experiments and the approach was verified on composites with known interfacial adhesion. The results showed that the use of functionalized polymer in PP/CaCO 3 composites resulted in adhesion strength one order of magnitude larger than without the coupling agent. The application of various surface modification techniques in PP/glass bead composites yielded different adhesion values covering a range of about one order of magnitude. The quantitative determination of interfacial adhesion makes possible the design and optimization of most surface modification techniques in particulate filled and short fiber reinforced composites.