Interlaminar Shear Properties Research Articles

Flexural and interlaminar shear response of novel methylmethacrylate composites reinforced with high-performance fibres

This experimental work presents a comparative study on the mechanical behaviour of novel infusible methylmethacrylate matrix (Elium®) composites reinforced with different types of high-performance fibres. A vacuum-assisted resin infusion process was employed to fabricate the laminates using carbon, basalt, Kevlar®, and high molecular weight polyethene (UHMWPE) fibres. Flexural and interlaminar shear properties of the composites were evaluated. Test results revealed that carbon fibre composites had superior flexural strength, stiffness and interlaminar shear stress as compared to the other composites tested. Further, composites containing Kevlar and UHMWPE fibres demonstrated significantly higher flexural strains to failure. Post-testing, specimens were examined using scanning electron microscopy (SEM). Microscopy revealed possible interfacial interaction differences based on the reinforcement fibre type, which was further confirmed by an analytical approach for analysing the flexural behaviour of various types of composites. The sequence of damage progression in specimens was also analysed.

A combined multilevel computational and experimental approach for interfacial screening and mechanical reinforcement of basalt fiber/polyamide 66 composites

Silane coupling agents (SCAs) can improve fiber-resin interface issues, yet selecting an appropriate SCA experimentally is resource-intensive. Herein, a multi-level screening method combining simulation and experiments is proposed to identify SCA-enhancing bonding between SCAs and polyamide 66 (PA66) and the basalt fiber (BF) −PA66 interface. SCAs with organic groups composed of N and O exhibited superior interaction with PA66 due to the more pronounced negative and positive electrostatic potential (ESP) distributions. In SCAs-grafted BF-PA66 models, SCAs not only altered BF surface nanostructure but also changed the arrangement of PA66 main chains from parallel to interpenetrating BF surface atoms. Besides, (3-ureapropyl)trimethoxysilane (SCA6) significantly improved BF-PA66 bonding, which was experimentally validated by enhanced interlaminar shear and mechanical properties. O atoms on SCA6 and PA66 are more electronically bound and have the smallest ESP extremum, providing strong polar interaction sites. Additionally, both simulations and experiments demonstrated a transformation from adhesive to cohesive failure.

Measurement of Interlaminar Shear Properties of Pultruded CFRP Composites Based on Modified DNS Specimens

A double-notch shear (DNS) test was modified for a measurement of interlaminar shear properties of pultruded carbon-fibre-reinforced polymer (CFRP) composites under moderate through-thickness compressive stresses, which were applied by torqued bolts. A range of failure criteria were presented to compare with experimental results. An attempt was made to predict the shear stress-strain relationship in the combined stresses with through-thickness compressive and shear stresses. Results indicate that the modified 2DNS specimen makes the shear surface of the specimen more uniform and reduces the peel stress at the notch tip. The 2DNS fixture made it easier to study the influence of composite interlaminar shear strength and shear stress-strain relationship under moderate through-thickness compression. The initial shear stiffness was not affected by moderate through-thickness compressive stresses. Moderate through-thickness compressive stresses on pultruded CFRP materials can increase interlaminar shear strength and ductility. Of all the failure criteria, the Mohr-Coulomb criterion was preferred to predict the enhancement of the shear strength under moderate through-thickness compression. Based on the Mohr-Coulomb criterion and the inverse solution of Ramberg-Osgood model, a unified equation was proposed and can effectively characterise the interlaminar shear stress-strain relationship under moderate through-thickness compression.

Effects of high temperature and strain rate on the impact-induced inter-laminar shear behavior of plain woven CF/PEEK thermoplastic composites

This paper aims to investigate the interlaminar shear properties and failure mechanisms of plain woven carbon fabric/polyetheretherketone (CF/PEEK) thermoplastic composites under high strain rate impact loads at different temperatures (25°C, 120°C, 295°C). A reliable hot air flow heating method with SHPB is creatively employed for short beam shear experiments. A multi-scale model was developed to predict the impact behavior of plain CF/PEEK composites. Both results show that the thermoplastic composites have strong strain rate and temperature dependence, and which are more sensitive to temperature effect. As the temperature increases, the thermoplastic composites are mainly affected by the softening effect of the matrix due to the glass transition temperature. The shear modulus and peak stress appear to decline at high temperatures, while the failure strain tends to increase. The damage mode changes from interlayer delamination cracking at the glassy state to shear fracture and fiber pullout at a highly elastic state. As the strain rate increases, the failure strain decreases, while the shear modulus and peak stress show the opposite trend. Fiber bundle breakage, debonding, matrix cracking, and significant interlayer delamination occur at high strain rates.

Study on mechanical properties and molecular simulation of nano‐SiO2‐modified hybrid fiber reinforced polymer bar under the dry and alkaline environment

AbstractFiber reinforced polymer (FRP) bars have received extensive promotion and application in the structural engineering. However, due to the limitations inherent in using single material, FRP reinforced concrete structures often encounter issues, such as brittle failure and inadequate energy dissipation, particularly in complex natural environments and under various loading conditions. In this study, the preparation of nano‐SiO2‐modified carbon/basalt hybrid FRP bars was carried out using the pultrusion‐winding process and ultrasonic treatment. The objective was to investigate the influence of the fiber volume ratio and mass fraction of nano‐SiO2 on the mechanical properties of FRP bars under drying and alkaline conditions. Molecular dynamics simulations were performed to construct interface models between fibers and epoxy resin in order to elucidate the toughening mechanism of nano‐SiO2 and the degradation mechanism in alkaline conditions. The research results show that elevating the substitution rate of carbon fibers and incorporating nano‐SiO2 doping bring about alterations in the brittle fracture characteristics of BFRP bars and enhance the post‐yield performance and interlaminar shear properties of hybrid FRP bars, concurrently mitigating the degradation of mechanical properties induced by exposure to alkaline solutions. MD simulations indicate that the addition of nano‐SiO2 improves the binding rate of hydrogen bonds between BF and epoxy resin, resulting in a higher interfacial energy between BF/epoxy resin compared to CF/epoxy resin. Moreover, nano‐SiO2 effectively mitigates the impact of alkaline solutions on the formation of interfacial hydrogen bonds. The findings of this study serve as a valuable reference for the design and application of FRP reinforced concrete structures.Highlights Nano‐SiO2 modified B/CFRP bars made via extrusion‐winding & ultrasonic treatment. Improved mechanical properties and plastic deformation in Nano‐SiO2 modified B/C FRP bars. Nano‐SiO2 inhibits B/CFRP bars degradation in alkaline solution. Nano‐SiO2 bind more at BF/epoxy than CF/epoxy interface. Nano‐SiO2 reduces alkaline solution effect on interfacial H‐bonding.

Effects of preform structure on microstructure and mechanical properties of long/short fiber‐coupled C/C–SiC composites

AbstractC/C–SiC composites with four different preform structures were prepared via chemical vapor infiltration and reactive melt infiltration (RMI). The effects of preform structure on the microstructure and mechanical properties of the C/C–SiC composites were thoroughly investigated. The results indicate that the porous C/C composites with multidirectional long/short fiber‐coupling exhibited consistent pore size distribution (diameter: 5–300 µm) and periodicity pore distribution characteristics. As the effective fiber volume fraction in the loading direction of the C/C–SiC composites increased from 11.71% to 21.04%, the tensile and flexural strength significantly increased by 64.44% and 44.03%, respectively, with minimal effect on compressive and interlaminar shear properties. The introduction of Z‐direction fiber, such as stitched structure, increased the compressive and interlaminar shear strength of the composites by 10.87% and 15.67%, respectively. A theoretical predictive model of ultimate tensile strength after modification was validated for application to the C/C–SiC composites prepared by RMI, through characterization of the volume fraction of each layered unit and the content of each component. However, the presence of defects caused by the stitched structure, such as fiber bending, occupancy, and pores, reduced tensile and flexural strength by 30.45% and 28.56%, thereby impacting the effectiveness of the predictive model negatively.

Effect of adding reinforcing phase to the interface and matrix on the interlaminar shear properties of multilayer-structured composites

Currently, poor mechanical properties limit the application of composite, especially the interlaminar shear strength (ILSS). Herein, this work employed a simple atomization deposition and co-blending method to introduce reinforcing phase on the interface and in the matrix, and then the unique multilayer-structured composites were fabricated by the technology of layer-by-layer assembly and hot-pressing. Benefiting from the presence of mechanical interlocking, hydrogen bonding, and van der Waals forces, the MXene on the interface and inside the matrix can both improve the ILSS of the composite. Specifically, when 0.5 wt% MXene nanosheets are deposited on the interface, the ILSS of the composite is increased by 21.41 %, and when 2 wt% MXene nanosheets are further introduced into the epoxy, the ILSS of the composite is improved by 55.58 %, reaching 59.96 MPa. Moreover, the ILSS of the composites shows good mechanical stability even after 30 days of storage. Besides, the failure modes of the composite were investigated, mainly including fiber debonding, matrix fracture and fiber breakage. This work adopts a facile and effective approach to prepare composites with excellent shear performance, which can provide more possibilities for the development of composites with high mechanical properties.

A review of the effect of hydrothermal aging on the mechanical properties of 2D fiber‐reinforced resin matrix composites

Abstract2D fiber reinforced resin matrix composites (2D FRRMC) are widely applied for aerospace, generator blades, and other high‐end equipment manufacturing fields due to their excellent mechanical properties. However, 2D FRRMC will face a variety of complex environments in the service process, and the long‐term complex environment will significantly impact the physical and mechanical properties of 2D FRRMC. It is necessary to understand and analyze the changes of materials during service. A comprehensive review of the research on the effect of hydrothermal aging on the mechanical properties and re‐ drying of 2D FRRMC in recent years was presented in this article, which contains interlaminar shear properties, compression properties, tensile properties, and aging mechanism, etc. Finally, the current challenges and prospects of 2D FRRMC were discussed. These discussions and proposed strategies will enlighten thoughts and offer ways to apply 2D FRRMC in complex environments better, study 2D FRRMC in complex environments, and study the effects of hydrothermal aging on materials in the future.

Evaluation of the bonding process and interlaminar shear properties of hybrid cross-laminated timber prepared with larch and OSB

Evaluation of the bonding process and interlaminar shear properties of hybrid cross-laminated timber prepared with larch and OSB

Enhancing Sustainability: Jute Fiber-Reinforced Bio-Based Sandwich Composites for Use in Battery Boxes.

The rising industrial demand for environmentally friendly and sustainable materials has shifted the attention from synthetic to natural fibers. Natural fibers provide advantages like affordability, lightweight nature, and renewability. Jute fibers' substantial production potential and cost-efficiency have propelled current research in this field. In this study, the mechanical behavior (tensile, flexural, and interlaminar shear properties) of plasma-treated jute composite laminates and the flexural behavior of jute fabric-reinforced sandwich composites were investigated. Non-woven mat fiber (MFC), jute fiber (JFC), dried jute fiber (DJFC), and plasma-treated jute fiber (TJFC) composite laminates, as well as sandwich composites consisting of jute fabric bio-based unsaturated polyester (UPE) composite as facing material and polyethylene terephthalate (PET70 and PET100) and polyvinyl chloride (PVC) as core materials were fabricated to compare their functional properties. Plasma treatment of jute composite laminate had a positive effect on some of the mechanical properties, which led to an improvement in Young's modulus (7.17 GPa) and tensile strength (53.61 MPa) of 14% and 8.5%, respectively, as well as, in flexural strength (93.71 MPa) and flexural modulus (5.20 GPa) of 24% and 35%, respectively, compared to those of JFC. In addition, the results demonstrated that the flexural properties of jute sandwich composites can be significantly enhanced by incorporating PET100 foams as core materials.

Pseudo-anisotropic damage model of randomly oriented strands (ROS) for reproducing flexural damage behavior

We developed a pseudo-anisotropic damage model of randomly oriented strands (ROS) reinforced thermoplastic composites for reproducing flexural deformation and damage behavior by finite element analysis (FEA). The damage model applied stress triaxiality to capture the differences in the damage initiations among the tensile, compressive, and shear stress states. The damage model also included equivalent damage propagation function depending on the interlaminar shear property of ROS. The developed FE model was focused on the characteristics that ROS composites show macroscopic in-plane isotropic and out-of-plane anisotropic mechanical properties because of the laminated structure of ROS. Furthermore, all of the material parameters in the FE model were identified by performing simple deformation tests. As a result, the flexural numerical simulation could reproduce the experimental flexural deformation and damage behaviors of ROS plates with different thickness despite a complex stress state including in-plane and out-of-plane stresses. The developed FE model has potential to evaluate the safety of ROS-manufactured structural components. The evaluation of safety by FEA constructed in this study can improve the applicability of ROS composites.

Interlaminar Shear Property and Strength Prediction Model for Hybrid Fiber-Reinforced Polymer Bar after Exposure to Simulated Concrete Environments

The load-transfer mechanism in the fiber-reinforced polymer (FRP) bars is different from that of the conventional steel bars. The efficiency of stress transfer in FRP bars mainly depends on the mechanical properties of matrix resin, fibers, and fiber/matrix interface, which are easily degraded after long-term exposure to concrete environment. Herein, the interlaminar shear properties of a novel carbon/glass hybrid fiber-reinforced polymer (C/G-HFRP) bar were experimentally investigated by the accelerated aging tests at 60°C to study the effects of the ratio of carbon to glass fiber volume fractions, distribution configuration of carbon fiber, total fiber volume fraction, exposure environment, and exposure period. Water uptake tests, scanning electron microscopy, and Fourier transform infrared spectroscopy were employed to explore the degradation mechanisms of exposed samples. The results indicated that the interlaminar shear strength (ILSS) retention of exposed C/G-HFRP bars was higher than that of the single glass-FRP bar, which was decided by tooth force and friction. In addition, the degradation of C/G-HFRP bars was also related to water uptake rate, and then waterproof coating and fiber modification are recommended to improve the durability of C/G-HFRP bars. Finally, a model of ILSS retention was proposed for the C/G-HFRP bars after exposure to different concrete environments.

Effects of irregular pores on the shear properties of the plane

Through section analysis and optical microscope observation of thick-section composite materials, it is found that there are significant differences in pore micro-characteristics of samples with different thicknesses. It is pointed out that the difference in pore micro-characteristics in the composite matrix is one of the reasons for the change in the interlaminar shear strength of composite materials. In this paper, irregular pore profiles are obtained through image processing, and the parameters to quantitatively characterize the microscopic characteristics are proposed. A randomly generated three-dimensional representative volume element (RVE) model including fiber, matrix, fiber/matrix interface, and pores. The effect of irregular pores with different sizes and distributions on the interlaminar shear strength of composite materials is given. The RVE numerical analysis results show that the interface failure between the fiber and the matrix near the pore causes damage. At the same porosity, the shear strength decreases with the increase of the maximum pore size. At the same time, the porosity concentration also has a significant effect on the interlaminar shear strength of thick section composite. The numerical results verify that the influence of pores on the interlaminar shear properties of thick-section composites is related to the microscopic characteristic parameters of pores.

Effect of carbon fiber surface treatment with HNO3 and KOH on the interfacial bonding of PMMA resin composite

Abstract This work studied the surface, interface state and physicochemical properties of HNO3-treated and KOH-treated carbon fiber. Poly(methyl methacrylate) (PMMA) composites were prepared by the autoclave molding process using surface-treated carbon fiber as reinforcements. The physical and chemical states of the carbon fiber surfaces and the micro-interface properties and interlaminar shear properties of the composites were studied. The results show that the surface of the HNO3-treated carbon fiber has more groove structure and higher surface roughness and thus forms a better physical bond with the resin matrix. Although the oxygen-containing functional groups of the two carbon fibers are equivalent, the surface oxygen of the HNO3-treated carbon fiber is relatively high, which is beneficial to form a better chemical bond with the matrix resin, and the interfacial shear strength is about 14% higher than that of the KOH-treated carbon fiber composite.

Mode II interlaminar shear behavior of needled/tufted interlocking composites

The needled/tufted interlocking fabric is a new fabric structure. At present, the mode II interlaminar shear behavior of needled/tufted interlocking composite has not been clarified. In this work, the needled/tufted interlocking fabrics and reinforced composites were fabricated, and the interlaminar shear behavior of mode II was studied experimentally and numerically, the mechanism of tufting effect on interlaminar shear properties of needled composites was revealed. The study found that the interlaminar shear properties of needled/tufted interlocking composites were greatly improved by tufted fiber bundles. The maximum failure load of the needled/tufted interlocking specimen increased 108.93%, and the interlaminar shear stress of the needled/tufted interlocking specimen improved by 89.39%. The interlaminar shear strength increased linearly with the increase of tufted fiber bundle implantation volume. The implantation pattern of tufted fibers had effected on interlaminar shear property. Under the same implantation volume, the thinner tufted fiber bundles and more implantation points were more beneficial to improve the interlaminar shear performance. The typical shear failure modes included matrix cracking, fibers pullout, and brittle fracture of tufted fiber bundles and needled fiber bundles. Moreover, a numerical simulation model of interlaminar shear behavior based on three cohesive zones (TCZMs) was proposed. The predicted displacement-load curves were highly in accord with the experiments. The error range was controlled within 1.08% - 3.76%. The simulation model could predict the mode II shear behavior of needled and tufted interlocking composites effectively, which was helpful to the early manufacturing process design of needled and tufted interlocking fabrics.

Bio-Based Pultruded CFRP Laminates: Bond to Concrete and Structural Performance of Full-Scale Strengthened Reinforced Concrete Beams.

This paper presents an experimental study about the use of innovative bio-based pultruded carbon-fiber-reinforced polymer (CFRP) laminates for structural strengthening. The bio-based laminates were produced in the framework of an applied research project (BioLam) using a resin system with 50% (wt.%) bio-based content, obtained from renewable resources. In the first part of the study, their tensile and interlaminar shear properties were characterized and compared with those of conventional oil-based CFRP laminates. In the second part of the study, the bond behavior to concrete of both types of CFRP laminates applied according to the externally bonded reinforcement (EBR) technique was assessed by means of single-lap shear tests performed on CFRP-strengthened concrete blocks; the experimental results obtained from these tests were then used in a numerical procedure to calibrate local bond vs. slip laws for both types of laminates. The final part of this study comprised four-point bending tests on full-scale EBR-CFRP-strengthened reinforced concrete (RC) beams to assess the structural efficacy of the bio-based laminates; these were benchmarked with tests performed on similar RC beams strengthened with conventional CFRP laminates. The results obtained in this study show that the (i) material properties, (ii) the bond behavior to concrete, and (iii) the structural efficacy of the developed bio-based CFRP laminates are comparable to those of their conventional counterparts, confirming their potential to be used in the strengthening of RC structures.

Fabrication and braiding angle effect on the improved interlaminar shear performances of 3D braided sandwich hybrid composites

While the interlaminar hybrid composites have been used widely and still remain in great demands, interlayer delamination, undesirable in most cases, keeps a common defect, due to the lack of interlaminar fiber-connection. Here, on the basis of the yarn interlacing rule in three-dimensional (3D) four-step braiding technology, 3D braided carbon fibers/Kevlar fibers sandwich (S_) hybrid composites with different braiding angles (S_20°, S_30° and S_40°) have been designed and fabricated with interlaminar fiber-connection. Short-beam shear tests were applied to evaluate the interlaminar shear performances of specimens. The in-situ strain maps during tests were characterized by digital image correlation (DIC) technique and specimen damages were observed via scanning electron microscope (SEM) and computed tomography (CT). Results showed that, comparing to the conventional co-cured laminated hybrid composites, 3D braided sandwich hybrid composites resisted the delamination effectively by the fiber-connection hybrid region. Braiding angle effect of 3D braided sandwich hybrid composites revealed that S_20° showed better deformability and higher structural toughness than their counterparts in S_30° and S_40°. The results presented in the current work would be helpful for the design and manufacturing of well structured hybrid preforms and composites with dramatically improved interlaminar shear properties.

Interfacial and interlayer enhancement of highly hydrophilic dual-affinity waterborne polyurethane sizing agent acting on carbon fiber/epoxy resin composites

Dual-affinity waterborne polyurethane (WPU) sizing agents with different solid concentrations were designed to achieve two-stage interfacial properties of carbon fiber (CF) and epoxy resin (EP) reinforced composites. The effects of hydrophilic monomer content on the emulsion dispersion of WPU sizing agents and the thermal properties of the coating films were investigated, and the best performing component was selected as the sizing agent of CF to prepare WPU treated-CF. The analysis focuses on the changes of surface morphology and roughness, ionic group types, tensile strength of CF before and after WPU sizing, and the interfacial properties, interfacial strengthening mechanism of CF/EP composites. Compared with conventional commercial CF, the WPU treated-CF shows a 4 % increase in surface free energy and a noticeable improvement in surface roughness and morphology. The wettability, compatibility and adhesion of WPU treated-CF/EP composites were improved according to the strong polar “similarity intermiscibility” between the strong polar functional groups in WPU and EP. Most importantly, the interfacial shear properties (IFSS) of WPU treated-CF/EP composites were improved by 17.2 % and the interlaminar shear properties (ILSS) were improved by 23.8 %. The dual-affinity WPU sizing agent optimizes the practical effect of CF/EP composites for applications such as instrument components and surface coatings used in new energy vehicles, high-speed rail trains, aerospace and provides a boost to the development of new environmentally friendly high-performance chemical coatings.

Manufacturing of flax- and glass-fibre reinforced thin-walled tubes and measuring their interlaminar shear properties by torsion tests

Recently, methods for determining interlaminar shear properties have been continuously developed to achieve homogeneous stress states and avoid edge effects. In this regard, the torsion test on tube specimens represents a setup with many advantages. Therefore, fibre composites made by a winding of glass and flax fibres were produced at a new type of mandrel, resulting in tubes with a wall thickness between 370 µm (glass) and 640 µm (flax). A new method for determining the shear strain is described in the context of the torsion test. The results are in line with analogous investigations, proving the validity of the new methodology.

Effects of Surface Properties of Fiber on Interface Properties of Carbon Fiber/Epoxy Resin and Its Graphene Oxide Modified Hybrid Composites.

In the present study, surface properties of three types of carbon fibers (CCF300, CCM40J, and CCF800H) on the interface properties of carbon fiber/epoxy resin (CF/EP) were analyzed. The composites are further modified by graphene oxide (GO) to obtain GO/CF/EP hybrid composites. Meanwhile, the effect of the surface properties of CFs and the additive graphene oxide on the interlaminar shear properties and dynamic thermomechanical properties of GO/CF/EP hybrid composites are also analyzed. The results show that the higher surface oxygen-carbon ratio of carbon fiber (CCF300) has a positive effect on improving the glass transition temperature (Tg) of the CF/EP composites. The Tg of CCF300/EP is 184.4 °C, while the Tg of CCM40J/EP and CCF800/EP are only 177.1 °C and 177.4 °C, respectively. Furthermore, deeper and more dense grooves on the fiber surface (CCF800H and CCM40J) are more conducive to improving the interlaminar shear performance of the CF/EP composites. The interlaminar shear strength (ILSS) of CCF300/EP is 59.7 MPa, and that of CCM40J/EP and CCF800H/EP are 80.1 MPa and 83.5 MPa, respectively. For the GO/CF/EP hybrid composites, graphene oxide with abundant oxygen-containing groups is beneficial to improve the interfacial interaction. Graphene oxide can significantly improve the glass transition temperature and interlamellar shear strength of GO/CCF300/EP composites fabricated by CCF300 with a higher surface oxygen-carbon ratio. For the CCM40J and CCF800H with lower surface oxygen-carbon ratio, graphene oxide has a better modification effect on the glass transition temperature and interlamellar shear strength of GO/CCM40J/EP composites fabricated by CCM40J with deeper and finer surface grooves. Regardless of the type of carbon fiber, the GO/CF/EP hybrid composites with 0.1% graphene oxide have the optimized interlaminar shear strength, and the GO/CF/EP hybrid composites with 0.5% graphene oxide have the maximum glass transition temperature.