Fiber Interfacial Shear Strength Research Articles

Improving the performance of alkali-activated slag mortar with electro/chemically treated carbon fiber textile

Alkali-activated slag is a widely used low-carbon binder. Incorporation of textile can mitigate the brittle weakness of alkali-activated composites. The bonding between fibers and matrix is critical for the performance of textile reinforced mortar. This paper is focused on the effect of different treatment methods on the bonding properties of carbon fiber in alkali-activated slag. The interfacial shear strength of fiber bundles in matrix was determined by the pull-out test. The flexural strength of the reinforced mortar was evaluated by a repeated bending. A scanning electron microscopy test was performed to characterize the interfacial properties of the fiber bundles. The results show that the interfacial shear strength of carbon fibers in matrix is improved by the electroplating with calcium silica slurry (CSS), impregnation in different solutions, and plasma treatments. An electroplating in CSS has the best improvement in the bonding strength with an increase by 620%. The CSS treatment increases the maximum flexural strength of CFT reinforced mortar with 22.5% and 30% at 7 and 28 d respectively, and it significantly inhibits the crack growth under the cyclic loading. This effect becomes more significant after a longer curing age. The electroplating treatment eliminates the cracks in the interface of fiber yarns. Slag reacts with the plated portlandite to strengthen the bonding between mortar and fiber bundles, so it has a better inhibiting effect on the crack growth after a longer curing.

Molecular dynamics simulation study on interfacial shear strength between calcium-silicate-hydrate and polymer fibers

The macroscopic mechanical performance of fiber reinforced concrete (FRC) is determined by the interfacial microstructure and the interfacial bonding properties between hydration products and fibers. This research is dedicated to study the interfacial shear strength, structure and dynamics between calcium-silicate-hydrate (C-S-H) and polymer fibers. To better understand the effects of fiber types on the interfacial shear strength, three kinds of fibers were investigated, including polypropylene (PP), polyvinyl alcohol (PVA) and polyacrylic acid (PAA). The calculation results indicate that the interfacial shear strength is closely related to the fiber types. The interfacial shear strength of fibers restricted in the C-S-H substrate was arranged in the following order PAA fiber > PVA fiber > PP fiber. After measuring the interfacial shear strength, the static molecular structure and dynamics properties, especially at the interface between the fiber and the C-S-H matrix, the cause for the interfacial shear strength discrepancy between different fibers was uncovered. It shown that the Ca atoms in the interface play an important role in the interfacial bonding interactions by the formation of OCSH-Ca-Opolymer connection. The H bonds can be formed between PAA/PVA fibers and C-S-H substrate, also provide some contribution for enhancing the interfacial bonding strength. The chemical bond stability revealed that the interfacial bonding strength of three fibers follows the order of PAA fiber > PVA fiber > PP fiber, which is consistent with the order of interfacial shear strength.

Improved out-of-plane strength and weight reduction using hybrid interface composites

Carbon fiber composites with increased fiber-to-matrix bonding are often susceptible to premature failure due to the creation of overly rigid interfaces. This paper investigates the use of electrochemically functionalised carbon fibers used in novel ‘hybrid interface’ arrangements to improve out-of-plane bending. An improvement of 103.6% in single fiber interfacial shear strength (IFSS) was able to improve out-of-plane strength by 33.6% for short beam shear laminates. However, by combining both functionalised and non-functionalised fibers in complex hybrid interface arrangements such as nature inspired turtle-shell interfaces and circular patterns, mechanical performance was improved significantly. A 170.9% increase to out-of-plane strength was observed using a turtle-shell arrangement which correlated to an 8.7% reduction in composite weight as compared to control fibers.

A novel and facile fabrication of polyphosphazene nanotube/carbon fiber multi-scale hybrid reinforcement and its enhancing effect on the interfacial properties of epoxy composites

The mechanical properties of carbon fiber (CF) reinforced composites are greatly dependent on the interfacial adhesion between fiber and resin matrix. Introducing nanoscale reinforcements into the interface is an effective approach to improve the interfacial adhesion of CF composites. In this paper, we proposed a facile and effective method for assembling poly(cyclotriphosphazene-co-4,4′-sulfonyldiphonel) nanotube onto CF surface as a novel multi-scale hybrid reinforcement through in situ template polymerization. The effects of surface modification on the surface and interface properties of CF and the resulting composite were investigated. After modification, the interfacial shear strength of fiber reinforced epoxy composites showed an increase of 26.4%. The reinforcing mechanisms were also analyzed, and the improvements on interfacial properties should mainly be attributed to mechanical interlocking effect. In addition, the modification even improved the fiber tensile strength by 6.6–16.3%, rather than deteriorating it.

The effect of surface modification on the properties of sisal fiber and improvement of interfacial adhesion in sisal/starch composites induced by starch nanocrystals

A facile approach was utilized to introduce starch nanocrystals (SNCs) onto sisal fiber (SF) to improve the interfacial adhesion between SF and starch. For this, fibers were treated with alkali and then subjected to cold plasma treatment to increase the accessibility with SNCs, which was confirmed through X-ray photoelectron spectroscopy (XPS). It was found that due to the influence of cold plasma treatment, new functional groups were introduced onto SF. The surface characteristics of SF were examined by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The observed results suggested that SNCs were successfully distributed onto SF. Tensile strength and interfacial shear strength of fibers treated under different conditions were calculated and compared through a two-parameter Weibull model. The highest interfacial shear strength of 3.05 MPa was obtained by Alkali-300 W-SNCs, which indicated an increase of 80.6% than untreated SF. It has also been proved that the starch nanocrystals produced hydrogen bonding and physical interlocking between sisal fiber and starch. Notably, the outcome of this investigation indicates that SNCs may be applied for the fabrication of high performance, environmentally friendly sisal/starch composites for a range of technological applications.

Analysis on the interfacial shear strength of fiber reinforced titanium matrix composites by shear lag method

Based on shear-lag method, two models for a single fiber push-out test are proposed to evaluate the interfacial shear strength of SiC fiber-reinforced titanium-matrix composites (TMCs). In the models, the effects of specimen parameters (such as specimen thickness and fiber volume fraction) on the interfacial shear strength are considered. The interfacial shear strengths of SCS-6/Ti-24-11 and SCS-6/Ti-15-3 composites are predicted using the model. The predicted results indicate that the models can be reliably used to predict interfacial shear stress of TMCs.

Influence of atmospheric pressure plasma treatment on surface properties of PBO fiber

In order to improve the interfacial adhesion property between PBO fiber and epoxy, the surface modification effects of PBO fiber treated by atmospheric pressure plasma jet (APPJ) in different time, atmosphere and moisture regain (MR) were investigated. The fiber surface morphology, functional groups, surface wettability for control and plasma treated samples were analyzed by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements, respectively. Meanwhile, the fiber interfacial shear strength (IFSS), representing adhesion property in epoxy, was tested using micro-bond pull-out test, and single fiber tensile strength was also tested to evaluate the mechanical performance loss of fibers caused by plasma treatment. The results indicated that the fiber surface was etched during the plasma treatments, the fiber surface wettability and the IFSS between fiber and epoxy had much improvement due to the increasing of surface energy after plasma treatment, the contact angle decreased with the treatment time increasing, and the IFSS was improved by about 130%. The processing atmosphere could influence IFSS significantly, and moisture regains (MR) of fibers also played a positive role on improving IFSS but not so markedly. XPS analysis showed that the oxygen content on fiber surface increased after treatment, and CO, OCO groups were introduced on fiber surface. On the other hand, the observed loss of fiber tensile strength caused by plasma treatment was not so remarkable to affect the overall performance of composite materials.

Interfacial shear strength of fiber reinforced soil

Abstract The interfacial mechanical interaction between the reinforcement and soil matrix is a key factor in controlling the engineering properties of reinforced soil. To evaluate the factors affecting the interfacial strength properties of polypropylene fiber (PP-fiber) reinforced soil, single fiber pull-out tests were performed by using a modified special apparatus. It has been found that the designed pull-out test is an efficient method to qualitatively obtain the interfacial peak strength (IPS) and interfacial residual strength (IRS) of fiber/soil. Both the IPS and IRS decrease with water content increase, while increase with increasing soil dry density. The cement inclusions dramatically improve the interfacial shear strength of fiber/soil, and the IPS and IRS increase with an increase in additives content and curing time. Finally, by using scanning electron microscopy (SEM), the micromechanical interaction behavior between soil particles and fiber reinforcement were discussed. The interfacial shear resistance of fiber/soil depends primarily on the rearrangement resistance of soil particles, effective interface contact area, fiber surface roughness and soil compositions, etc.

P.261 Massive mandibular idiopathic osteolysis: A new syndrome?

In order to improve the interfacial adhesion property between PBO fiber and epoxy, the surface modification effects of PBO fiber treated by atmospheric pressure plasma jet (APPJ) in different time, atmosphere and moisture regain (MR) were investigated. The fiber surface morphology, functional groups, surface wettability for control and plasma treated samples were analyzed by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements, respectively. Meanwhile, the fiber interfacial shear strength (IFSS), representing adhesion property in epoxy, was tested using micro-bond pull-out test, and single fiber tensile strength was also tested to evaluate the mechanical performance loss of fibers caused by plasma treatment. The results indicated that the fiber surface was etched during the plasma treatments, the fiber surface wettability and the IFSS between fiber and epoxy had much improvement due to the increasing of surface energy after plasma treatment, the contact angle decreased with the treatment time increasing, and the IFSS was improved by about 130%. The processing atmosphere could influence IFSS significantly, and moisture regains (MR) of fibers also played a positive role on improving IFSS but not so markedly. XPS analysis showed that the oxygen content on fiber surface increased after treatment, and CO, OCO groups were introduced on fiber surface. On the other hand, the observed loss of fiber tensile strength caused by plasma treatment was not so remarkable to affect the overall performance of composite materials.

Interfacial reinforcement in composites with PPT aramid fiber modified by network-intercalation method

—A novel surface treatment for poly(p-phenylene telephthalamide) (PPTA) fiber is performed with silanes and urethane binder that are usually used as sizes for glass fiber treatment. The PPTA used for the surface treatment is modified by a spinning process to make the gaps between PPTA crystallites open. In this treatment, supercritical carbon dioxide fluid method is used to impregnate the sizing molecules into open gaps in PPTA fiber. After the impregnation, the fiber is heated at 100–170°C to make the gaps close and turn open-gapped fiber to the normal type of PPTA modified with sizes. The interfacial shear strength of fiber to epoxy resin is measured by microdroplet method. The modified PPTA improves the interfacial shear strength by ca. 67% to the interfacial shear strength given by normal PPTA without treatment. Those improvements are 33% without heating, 18% with only silanes, and 12% with only urethane instead of the mixture of silane and urethane. In addition, the fiber strength shows no remarkable decrease after the treatment.

Rf Plasma Polymerisation for the Improvement of Interfacial Adhesion between Glass Fibres and Polybutene-1

Radio frequency (RF) plasma polymerisation is used to treat glass fibres to improve the interfacial adhesion between polybutene-1 and glass fibre. After the glass fibres were treated with coupling agent, four different monomers were polymerised onto the surface by plasma. The plasma polymers changed the surface morphology and surface free energy of the fibre surfaces. The experimental results indicate that a grain-like surface induces a transcrystalline layer to form onto the fibre surface to improve the polybutene-1/glass fibre interfacial shear strength relative to glass fibres treated with coupling agent only. The glass fibre treated with coupling agent, then treated with acrylonitrile and styrene increased the interfacial adhesion strength by 71% and 78%respectively. Glass fibre surfaces treated with grain-like organosilicon, then plasma polymerised tetramethylsilane (ppTMS) and hexamethyldisiloxane (ppHMDSO), allow a transcrystalline layer to form and this increases the interfacial shear strength by 187% and 180% respectively, achieving 100% and 97% higher strength than when treated with coupling agent only.

EVALUATION OF THE HYBRID EFFECT OF HYBRID COMPOSITE FROM THE VIEWPOINT OF STRENGTH OF BRIDGING FIBERS IN A CRACK

The method of the analysis of a crack with bridging fibers in an infinite orthotropic elastic plate under remote uniform tensile stress is utilized to evaluate the mechanical properties of a hybrid composite with plual kinds of reinforcement fibers. Based on the evaluation of the tensile stress of the bridging fibers, the increment of the tensile stress loaded on the plate of the hybrid composite is confirmed by comparing the tensile stress calculated for the plate of composite reinforced by only one kind of fiber, which is the parent composite of the hybrid composite. The increment is affected by the interfacial shear strength of fiber and matrix, the length of crack and the number of bridging fibers.

Fiber-Matrix Adhesion and Its Effect on Composite Mechanical Properties. III. Longitudinal (0°) Compressive Properties of Graphite/Epoxy Composites

An experimental investigation was performed to quantify the relationship between fiber-matrix adhesion as determined by single fiber interfacial shear strength tests with the compressive properties and failure modes of unidirectional graphite/epoxy com posites. The compression tests were conducted on three identical sets of composites differ ing only in their fiber-matrix interfacial shear strength. The interfacial shear strength was varied by using the same graphite fibers with different surface treatments, namely un treated, surface treated, and surface treated and coated with a thin layer of epoxy. The sur face treatment changed the interfacial shear strength by more than a factor of two, while the properties of the fibers remained unchanged. The experimental results show that the fiber surface treatment affects the compressive modulus only marginally. However, the compressive strength and maximum compressive strain were highly sensitive to the fiber surface treatment. Both the strength and maximum strain increased with the interfacial shear strength. The fracture surface analysis revealed that when the fiber-matrix inter facial shear strength was low the compressive failure occurred due to delamination and global delamination buckling. At intermediate values of the interfacial shear strength, the compressive failure occurred due to shear failure driven by inphase microbuckling of fibers. The composites having the highest values of the interfacial shear strength yielded "stepped" fracture surfaces showing compressive failure of fibers in several planes perpen dicular to the fiber axis.

Fiber-Matrix Adhesion and Its Effect on Composite Mechanical Properties: I. Inplane and Interlaminar Shear Behavior of Graphite/Epoxy Composites

An experimental investigation was performed to establish the relationships between fiber-matrix adhesion as determined by single fiber interfacial shear strength tests with the inplane and interlaminar shear properties of graphite/epoxy composites. ±45°-tension, Iosipescu, and short beam shear tests were conducted on three identical sets of composites differing only in their fiber-matrix interfacial shear strength. The fiber-matrix interphase and consequently the interfacial shear strength was varied by using the same graphite fiber was different surface modifications, namely untreated, surface treated, and surface treated and coated with a thin layer of epoxy. The surface modification changed the interfacial shear strength by more than a factor of two, while the properties of fibers remained unchanged. The experimental results showed that both inplane and interlaminar shear strengths increased approximately in the same ratio as the interfacial shear strength, however, the inplane shear modulus was relatively insensitive to the fiber surface modifications. The fracture surface analysis revealed that when the fiber matrix interfacial shear strength was increased from low to intermediate to high values, the major failure modes changed from primarily interfacial failure to a combination of interfacial and matrix failure to primarily matrix failure, respectively, in a manner identical to that observed with the single fiber fragmentation tests.

The Interfacial Bond Strength in Glass Fibre-Polyester Resin Composite Systems Part 2. The Effect of Surface Treatment

Abstract The effect of surface treatments on the bond strength in glass fibre-polyester resin composites has been investigated using single fibre interfacial shear strength specimens and the short beam shear test for interlaminar shear strength. A range of bond strengths was obtained by using, either alone or in combination, the various components of the size formulation which is normally applied to the fibres, so that the interaction between the glass surface and the polyester ranged from Van de Waal forces through hydrogen bonding to covalent bonding, the bond strength increasing in that order. The relative contribution to bond strength of mechanical bonding due to thermo-mechanical mismatch between the two components and of chemical bonding or physical interaction between the three phases, glass-surface treatment-resin, has been evaluated and found to be one third and two thirds respectively.