Interlaminar Shear Tests Research Articles

Spinning waste as reinforcement for epoxy composites: mechanical performance

The present research work studies the feasibility of using waste cotton fibres from carding machines as a reinforcing material in epoxy resin matrix for composite fabrication. Waste cotton fibres were utilized to produced thick paper with an areal density of 150 g/m2. The physico-chemical properties of the produced papers were evaluated by X-ray diffraction methods, chemically and tensile testing. Composites samples were prepared using modified paper with epoxy resin, maintaining with different fibre content (20%, 30% and 40 wt%). The mechanical properties of the composite were evaluated by the tensile, flexural and interlaminar shear test. The tensile fracture behavior of the composites was investigated by scanning electron microscopy (SEM). The tensile strength, flexural strength and inter laminar shear strength (ILSS) of 40% fibre content composite in the machine direction were found to be 48, 54 and 6.1 MPa respectively. The results indicate that waste cotton fibers can be an excellent reinforcing material for composite production.

Static behavior of thick flax/epoxy composite laminates: multi-instrumentation mechanical failure analysis

The use of thick composites in civil engineering and aeronautics fields is becoming increasingly common in primary or secondary structures, and natural fiber composites present a valuable alternative in terms of mechanical performance, cost and environmental impact. Investigating the mechanical characteristics and damage mechanisms that occur in thick flax/epoxy laminates is the primary objective of this research. Firstly, multi-instrumented bending tests and interlaminar shear tests were carried-out to assess the mechanical properties and failure characteristics of the composite. This multi-instrumentation concerns, the Acoustic Emission and the Digital Image Correlation techniques. In addition, postmortem observations utilizing Computed Tomography (CT) Scan and scanning electron microscopy (SEM) were carried out. Finite Elements and analytical models were proposed to evaluate the mechanical response. At the macroscale, results demonstrate a good correlation in the elastic zone between the numerical, analytical and the experimental. However, at the mesoscale the correlation is less evident especially close to the final failure of the laminate. Based on SEM and X-ray tomography images, the differences recorded are related mainly to the plies thickness variations and the waviness phenomenon induced by the manufacturing process.

Study on the preparation and mechanical behavior of carbon fiber reinforced aluminum matrix composites stator blade

Study on the preparation and mechanical behavior of carbon fiber reinforced aluminum matrix composites stator blade

Performance and Life Cycle Assessment of Composites Reinforced with Natural Fibers and End-of-Life Textiles

The growing need for materials that are eco-friendly and sustainable in the industrial sector has shifted focus from synthetic fossil to natural fibers, alongside the utilization of recycled polymer textiles. This research introduces a novel method for using end-of-life textiles, such as polyester and polyamide fabrics, in the production of composite materials, aiming to lessen textile waste and enhance material longevity. The mechanical attributes of flax fabric (FF), flax–recycled polyamide fabric (F/RPA), and flax–recycled polyester fabric (F/RPES) composite laminates are assessed through tensile, flexural, interlaminar shear, and Charpy impact tests. The study revealed that the addition of end-of-life synthetic fibers improves tensile strength, while the trend in modulus values suggests that flax provides a high degree of stiffness to the composites, which is moderated by the addition of synthetic fibers. This effect is consistent across both tensile and flexural testing, although the impact on stiffness is more significant in bending. The inclusion of polyester fibers in the composite laminate resulted in significant enhancements, with an 11.1% increase in interlaminar shear maximum force, a 17.4% improvement in interlaminar shear strength, and a 67.1% rise in un-notch impact energy, compared to composites made with only flax fiber (FF). The microscopic examination uncovered the internal structure and demonstrated a clear, strong bond between the polyester and polyamide fiber layers with the flax fibers. Additionally, the life cycle assessment revealed that the F/RPES composite had less environmental impact than FF and F/RPA in all 18 categories analyzed. This indicates that the environmental footprint of producing F/RPES is smaller than that of both FF and F/RPA.

Optimising Recycling Processes for Polyimine-Based Vitrimer Carbon Fibre-Reinforced Composites: A Comparative Study on Reinforcement Recovery and Material Properties.

We investigated the recycling process of carbon fibre-reinforced polyimine vitrimer composites and compared composites made from virgin and recycled fibres. The vitrimer matrix consisted of a two-component polyimine-type vitrimer system, and as reinforcing materials, we used nonwoven felt and unidirectional carbon fibre. Various diethylenetriamine (DETA) and xylene solvent ratios were examined to find the optimal dissolution conditions. The 20:80 DETA-xylene ratio provided efficient dissolution, and the elevated temperature (80 °C) significantly accelerated the process. Scaling up to larger composite structures was demonstrated. Scanning electron microscopy (SEM) confirmed effective matrix removal, with minimal residue on carbon fibre surfaces and good adhesion in recycled composites. The recycled nonwoven composite exhibited a decreased glass transition temperature due to the residual solvents in the matrix, while the UD composite showed a slight increase. Dynamic mechanical analysis on the recycled composite showed an increased storage modulus for nonwoven composites at room temperature and greater resistance to deformation at elevated temperatures for the UD composites. Interlaminar shear tests indicated slightly reduced adhesion strength in the reprocessed composites. Overall, this study demonstrates the feasibility of recycling vitrimer composites, emphasising the need for further optimisation to ensure environmental and economic sustainability while mitigating residual solvent and matrix effects.

Exploring the impact of hybridization on green composites: pineapple leaf and sisal fiber reinforcement using poly(furfuryl alcohol) bioresin

Abstract This study aimed to examine the mechanical and physical characteristics of hybrid composite prepared using bio-epoxy reinforced with natural fibers extracted from pineapple leaf (PLF) and sisal (SF). The hand lay-up technique was utilized to fabricate the hybridized composite from bi-directional pineapple leaf fiber and sisal fibers using various stacking sequences. In order to understand the impact of hybridization on these composites, physical properties including density, percentage volume of fiber (PVF), and water absorption capacity were ascertained for hybrid composite. In addition, the mechanical characteristics like the tensile, fracture toughness, flexural, and interlaminar shear (ILSS) tests were investigated. Poly(furfuryl alcohol) was prepared and used as bioresin and it was apparent that the addition of more PLF in terms of PVF into hybridized composites, the properties flexural, tensile, and ILSS of the bio-epoxy composites were notably improved. The mechanical properties of hybridized composites were markedly impacted by the stacking order. Inference revealed that the composite attained the maximal tensile strength of 70.8 MPa for alternative sequence of SF and PLF. The composite which contained SF on the outside, had outperformed compared to other hybrid composites in terms of fracture toughness (3302.3 J/m2) and interlaminar shear strength (16.1 MPa).

Investigation of the interfacial bonding of new and old pavement materials for pothole applications: Bonding materials optimization, mechanical properties and structural performance

Investigation of the interfacial bonding of new and old pavement materials for pothole applications: Bonding materials optimization, mechanical properties and structural performance

Durability of hybrid flax fibre-reinforced epoxy composites with graphene in hygrothermal environment

Durability of hybrid flax fibre-reinforced epoxy composites with graphene in hygrothermal environment

Redox cationic frontal polymerization: a rapid curing approach for carbon fiber-reinforced composites with high fiber content

Conventional frontal polymerization processes for epoxy-based composites rely on cations and radicals generated by a short (and local) light or heat stimulus in the presence of an iodonium salt and a radical thermal initiator. However, due to heat losses, the propagation of the exothermic curing front is often limited by sample geometry and filler concentration. Redox cationic frontal polymerization (RCFP) is a promising approach to radically expand the composition and design options of frontally cured epoxy-based composites. By adding stannous octoate as reducing agent, a higher number of radicals and cations are generated at lower temperature, which yields highly cured composite even at elevated filler content. In the current study, RCFP was used to cure standard unidirectional carbon fiber-reinforced composites based on a commercially available epoxy resin and the properties were compared with its anhydride hardener-cured counterpart. Cure degree and thermal properties of the resins were determined by ATR FT-IR spectroscopy and DMA analysis. Subsequently, unidirectional composites with a fiber volume content of ~ 60% were produced via vacuum infusion and subjected to DMA, tensile, compression, and inter-laminar shear tests. The results showed a remarkable similarity between mechanical properties of RCFP and anhydride hardener-cured composites. The RCFP-cured composites exhibited even a higher damping resistance and compression strength than anhydride hardener-cured composites. The results show that RCFP allows for a significant reduction in the curing time (from several hours to 60 min), while it yields composites with properties comparable to classic anhydride-cured systems.Graphical abstract

Influences of Fiber Volume Content on the Mechanical Properties of 2D Plain Carbon-Fiber Woven Composite Materials.

The influence of fiber volume content on the mechanical properties of two-dimensional (2D) plain carbon-fiber woven composites is a crucial concern that necessitates immediate attention for large-scale applications in wind turbine blades. In this study, various mechanical tests were conducted on 2D plain carbon-fiber woven composites with different fiber volume contents, and the influences of fiber volume content on the mechanical properties and failure mode of the composite material were analyzed. Using carbon fiber as reinforcement and epoxy resin as a matrix, three types of plates with fiber volume contents of 47%, 50% and 53% were fabricated by using autoclave technology. The tensile, compression and interlaminar shear tests of the two-dimensional woven composites were carried out using MTS series testing machines. The influences of fiber volume content on tensile strength and modulus, compressive strength and modulus, interlaminar shear strength and shear strain energy were investigated. Additionally, the progressive damage development of these two-dimensional woven composites under different stress states was studied using scanning electron microscopy (SEM). The results indicate that the tensile strength and compressive strength increase almost linearly with the increase in fiber volume content, while the interlaminar shear strength increases slowly at low fiber volume content and rapidly at high fiber volume content. The tensile modulus of elasticity slightly increases as the fiber volume content increases, whereas the compressive modulus remains stable at low fiber volume content but gradually decreases at high fiber volume content. With the increase in fiber volume content, the shear strain energy of the specimen increases significantly.

Interfacial properties of carbon fiber‐reinforced biobased resin composites by single fiber fragmentation, fiber push‐out, and interlaminar shear strength

AbstractThe present study examines the interfacial properties of carbon fiber biobased resin composites by comparing the test methods such as the single fiber fragmentation test, fiber push‐out test, and interlaminar shear strength test. The composites were fabricated using a cold vacuum‐assisted resin infusion method for the preparation of fiber push‐out and interlaminar shear test specimens. The interfacial adhesion from the three different test methods is analyzed and compared to determine their relative effectiveness in evaluating interfacial adhesion. Plasma treatment is performed on the carbon fibers and the interfacial shear stress is evaluated by conducting the push‐out test. The surface characterization of the carbon fibers is done by scanning electron microscopy and x‐ray photoelectron spectroscopy to investigate the influence of the plasma treatment on the fiber surface. Plasma treatment resulted in significant improvement in the interfacial adhesion between the fiber and matrix.Highlights Analysis and comparison of interfacial adhesion by several test methods. Single fiber fragmentation and push‐out tests with IFSS of 40.5 and 42.2 MPa. Plasma surface treatment improved the IFSS by 88.1%. Surface characterization of treated and untreated fibers by SEM and XPS.

High strength, anti-static, thermal conductive glass fiber/epoxy composites for medical devices: A strategy of modifying fibers with functionalized carbon nanotubes

Abstract A series of aliphatic amine-functionalized multiwalled carbon nanotubes (MWCNTs) wherein varied secondary amine numbers were grafted on the MWCNTs’ surface were synthesized and further dispersed onto the glass fibers for reinforcing epoxy-based composites. By tuning secondary amine numbers of aliphatic amines, the dispersion of MWCNTs and ultimately mechanical, thermal, and conductive properties of epoxy-based composites could be adjusted. Using an optimal secondary amine number of aliphatic amine (triethylenetetramine), the interlaminar shear strength, tensile strength, and flexural strength of epoxy-based composite increased by 43.9%, 34.8%, and 35.0%, respectively; the work of fracture after interlaminar shear tests increased by 233.9%, suggesting strengthening/toughening effects of functionalized MWCNTs; significant reduction in surface resistance and increased thermal conductivity were also obtained, implying the superior conductive properties for composites. This work offers a new strategy for designing fiber-reinforced composites with high strength, excellent antistatic properties, and good thermal conductivity for medical device applications.

Ultrahigh-temperature mechanical behavior and failure mechanisms of SiCf/SiC composites

Ultrahigh-temperature mechanical behavior and failure mechanisms of SiCf/SiC composites

Shear performance degradation of basalt fiber‐reinforced polymer bars in seawater environments: Coupled effects of seawater sea‐sand geopolymer mortar coatings and sustained loading

AbstractGeopolymers, as a promising substitute for ordinary cement, exhibit different coating effects with regard to the durability of basalt fiber‐reinforced polymer (BFRP) bars. In this study, a comparative investigation was carried out on the shear performance of prestressed BFRP bars coated with seawater sea‐sand geopolymer mortar (SSGM). The alkaline content of the SSGM was 4% or 6%. The prestress level was 20% of the ultimate tensile strength at room temperature. The immersion temperatures were room temperature (RT), 40, or 60°C. Interlaminar shear tests and transverse shear tests were conducted at each period (30, 60, 120, and 240 days). The results showed that BFRP bar coated with 6% alkaline content exhibited a slightly higher degradation of shear strength. Furthermore, the prestress developed microcracks in the bars and weakened the interface between the fiber and resin matrix, particular at the elevated temperature. This led to further degradation of the BFRP bars. Additionally, a comparison was made between the shear strength results of BFRP bars coated with SSGM and those coated with ordinary portland concrete or seawater sea‐sand concrete, revealing that the long‐term shear performance of BFRP bars was less negatively impacted by the SSGM coating.Highlights Coupled effects of SSGM coatings and sustained loading on the degradation of BFRP bars are investigated. SSGM provides better protection for BFRP bars than cement‐base concrete. Alkaline content of activator in SSGM has insignificant impact on the BFRP degradation.

Hygrothermal aging effects on fiber-metal-laminates with engineered interfaces

Hygrothermal aging effects on fiber-metal-laminates with engineered interfaces

An investigation of bamboo shear test methods and the influence of heat on bamboo shear strength

An investigation of bamboo shear test methods and the influence of heat on bamboo shear strength

Enhanced interfacial and mechanical properties of glass fabric/epoxy composites via grafting silanized carbon nanotubes onto the fibers

AbstractFor enhancing the interfacial adhesion of glass fabric (GF)/epoxy composites, silanized multi‐walled carbon nanotubes (MWCNTs) were used to treat GF surface, where carboxyl MWCNTs were functionalized by silane coupling agents based on the covalent or non‐covalent bonding, followed by the vacuum infusion process of laminated composites. A detailed study was employed to confirm the effects of silanized MWCNTs uniform dispersion and interfacial properties of resultant composites. Making full use of suitable silane coupling agents (γ‐aminopropyltriethoxysilane) treatment, the uniform MWCNTs dispersion and strong fiber/matrix interfacial adhesion could be achieved. Compared with the control sample, flexural and interlaminar shear strengths of resultant composites were enhanced by about 24% and 22%, respectively, indicating superior mechanical strength for composites; flexural modulus and storage modulus in the glassy state were improved by about 36% and 68%, respectively, suggesting higher stiffness for composites; the work of fracture (Wf) under interlaminar shear tests was raised by about 188%, revealing better interlaminar fracture toughness of composites. In addition, glass transition temperature of resultant composites also increased. This work provides a guiding strategy for manufacturing fiber‐reinforced composites requiring adjustable strength, stiffness, and toughness.Highlights Silane coupling agent was grafted on MWCNTs by covalent/non‐covalent bonding. Active groups of silanized MWCNTs induced crosslinking reactions with matrix. Silanized MWCNTs dispersion and glass fiber/matrix adhesion were improved. Strengthening/toughening mechanisms of laminated composites were analyzed.

Improving corrosion resistance of BFRP bars by coating CNTs modified resin in simulated pore solution of seawater sea sand concrete

The corrosion of basalt fiber-reinforced polymer (BFRP) bars restricts their use in alkaline concrete structures. However, developing high-performance resin can improve the anti-alkaline corrosion of BFRP bars. This work investigates the alkaline resistance of BFRP bars by coating carbon nanotubes (CNTs) modified epoxy resin incorporating varying CNTs contents (0, 0.1, 0.3, and 0.5 wt%). The durability of untreated and treated BFRP bars with CNT-modified resin was evaluated using water uptake, transverse shear, and interlaminar shear tests. Scanning electron microscopy (SEM) and X-ray micro-computed tomography (micro-CT) were also used to observe the surface corrosion morphology and interior deterioration of BFRP bars, respectively, while Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were applied to analyze the resin deterioration of BFRP bars. It was found that CNTs modified resin can significantly improve the alkaline resistance of BFRP bars. After 180 d of immersion, the interlaminar shear strength (ILSS) retention of untreated BFRP bars is 31.8%, while it is 63.3, 75.0, 91.3, and 93.7% for BFRP bars treated with 0, 0.1, 0.3, and 0.5 wt% CNTs modified resin, respectively. The improvements in ILSS retention of BFRP bars treated with 0.5 wt% CNTs modified resin are 61.9% and 30.4% more than untreated and pure resin-treated BFRP bars, respectively. BFRP bars treated with 0.3 and 0.5 wt% CNTs modified resin exhibit insignificant resin hydrolysis and less porosity than untreated BFRP bars. The effective prevention of hydroxyl ions into the interior of BFRP bars and the enhancement of the anti-crack behavior of resin by CNTs are the leading causes of corrosion resistance improvement in BFRP bars. The outcomes of this study provide insights into using CNTs modified resin to improve the durability of BFRP bars in marine concrete structures.

Failure analysis and engineering mechanics modeling methods of a stitched ceramic sandwich structure

Failure analysis and engineering mechanics modeling methods of a stitched ceramic sandwich structure

Investigations on physical, mechanical, morphological and water absorption properties of ramie/hemp/kevlar reinforced vinyl ester hybrid composites

AbstractStructural uses in the vehicle, aerospace, and sporting goods industries are being supplanted by hybrid composites that utilized natural fibers as reinforcements. The main focus of this work is to fabricate and characterize the ramie, hemp, and kevlar fabric reinforced hybrid vinyl ester composites. The composite laminates were fabricated via economically feasible and flexible hand lay‐up technique. Overall six composites were prepared by varying the stacking sequence, including both hybrid and non‐hybrid composites. The prepared composites were subjected to physical analysis (density, void fraction), mechanical tests (tensile, flexural, interlaminar shear, and impact test), morphological analysis (scanning electron microscopy), and water absorption test. The hybrid composites exhibited lesser void percentage than the non‐hybrid composites. The mechanical properties were maximum for kevlar fabric skinned with core natural fabric reinforced composites (L‐5, L‐6) due to hybridization of highly strengthened kevlar fabrics. Moreover, the number fabric layers reinforced to achieve the standard thickness also affected the mechanical properties. All composite morphologies exhibited the same failure characteristics, including transverse interlaminar shear cracking, microbuckling, and fiber rip. The texture of the Kevlar yarns is uniform, but the texture of the natural fabric yarns is relatively less uniform. In comparison to the salt water medium, the percentage of water absorbed by composites in normal and distilled water was greater. This is due to the presence and accumulation of salt particles on the surface of the materials, which inhibits the action of water molecules, resulting in a drop in the proportion.