Glass Fiber-reinforced Epoxy Research Articles

Structural health monitoring of scarf bonded repaired glass/epoxy laminates interleaved with carbon non-woven veil

Bonded repair patches/joints often introduce vulnerabilities in composite laminates, making them prime candidates for structural health monitoring (SHM). In this study, stepped-scarf bonded joints were manufactured using glass fibre-reinforced epoxy laminates as representative repair patches, and a novel SHM approach through the electrical resistance change method was applied. To establish an electrically conductive path within the stepped-scarf joint, non-woven carbon fibre veils with areal weights of 10 g/m² and 20 g/m² were interlaid along the stepped bondline. Two types of tensile tests were performed. In the first set of tests, the stepped-scarf joints underwent monotonic quasi-static tensile loading until the bondline was completely fractured (catastrophic failure) and the change in electrical resistance was continuously monitored. The failure stress of the joint with a 10 g/ m² carbon veil was only marginally decreased (∼2 %) in comparison with that of the joints without a carbon veil, while the failure stress of the joint with a 20 g/m² carbon non-woven veil was considerably decreased (by ∼9 %). However, the joints with 10 g/m² and 20 g/m² carbon veils exhibited a significant change in electrical resistance (∼200 % and ∼1000 %, up to full failure, respectively). Simultaneously, the change in electrical resistance was used for the detection of damage initiation and progression, supported by digital images taken during the tests. In the second set of tests, the joints were subjected to a cyclic tensile loading/unloading regime and the change in electrical resistance was monitored. A significant amount of permanent change in resistance during the unloading phases (up to 120 % in the bondline with a 20 g/m² veil) was observed, providing insights into the laminate and bondline damage evolution. In addition, thermal images obtained with the joule heating method in the cyclic tensile tests were used to confirm the damage detected with the electrical resistance change method. Moreover, the micrographs from the fracture surfaces indicated that the variations in electrical resistance change are largely caused by damage occurring within or near the carbon veils. In conclusion, the results demonstrate that the presented SHM approach, which incorporates carbon non-woven fibre veils within non-conductive laminate composites, holds promise for monitoring damage initiation and propagation in repaired composite laminates as well as adhesively bonded composite laminate joints, without adversely influencing the structural integrity of the bondline.

Design and fabrication of an accelerometer structure using glass fiber reinforced epoxy resin for seismic P-wave early warning

Earthquake early warning represents a vital and effective strategy for mitigating earthquake-related losses. Among the existing sensors for earthquake early warning, MEMS accelerometers involve complex manufacturing process, leading to high research and development costs and long cycles. Traditional mechanical sensors are bulky, costly, hence not suitable for large-scale, high-density monitoring network. In this study, a low-cost accelerometer using glass fiber reinforced epoxy resin is proposed for longitudinal seismic waves (P-waves) early warning. Both theorical and finite element analysis are carried out to define and optimize the initial structure of the accelerometer. A pre-deformation structure is implemented into the spring suspension system to offset the influence of the sensor’s gravity, so that a self-balanced state in the direction of gravity is achieved. The simulation results show that the accelerator can achieve an eigenfrequency of 12.67 Hz, a Q-value of 49.2, and mechanical thermal noise of 1.72×10-9g/Hz. Based on the simulation results, the accelerometer’s structure is processed using a computer numerical control (CNC) milling machine, and tested by collecting the voltage signals when the accelerometer’s structure undergoes an impact in the direction of the gravity. The measured eigenfrequency is around 10 Hz, and the signal attenuation rate closely aligns with the simulation results. The accelerometer structure has dimensions within 6 cm and a relatively simplified manufacturing process, making it a cost-effective solution for the development of large-scale, high-density earthquake early warning systems.

Effects of Dolomite Geopolymer Filler on Mechanical Properties of Glass Fibre Reinforced Epoxy Composite

Effects of Dolomite Geopolymer Filler on Mechanical Properties of Glass Fibre Reinforced Epoxy Composite

In Situ Microscopy of Fatigue-Loaded Embedded Transverse Layers of Cross-Ply Laminates: The Role of an Inhomogeneous Fiber Distribution

Composites with continuous fiber reinforcement offer excellent fatigue properties but are tedious to characterize due to anisotropy and the interplay of fatigue properties, processing conditions, and the constituents. The global fiber volume content can affect both monotonic and fatigue strength. This dependence can increase the necessary testing effort even when processing conditions and constituents remain identical. This work presents an in situ edge observation method, enabling light microscopy during loading. As a result, digital image correlation can be employed to study local strains at cracking sites on the scale of fiber bundles. The geometric influence on fatigue damage is examined in non-crimp fabrics of glass and carbon fibers. Two epoxy resins (one modified by irradiation) are investigated to verify the geometric influence under changed polymer properties. The microscopy-based image correlation revealed that damage forms at very low global strains of only 0.2–0.3% in glass fiber-reinforced epoxy laminates. For carbon fiber-reinforced epoxy, laminate cracking was found to emanate mainly from regions containing stitching fibers. Across both reinforcements, irradiation treatment led to delayed cracks, emanating from interfaces. This detailed analysis of the damage formation is used as a basis for proposed applications of the in situ strain information.

Impact response and compression-after-impact properties of foam-core sandwich composites incorporating scrap tyre rubber particles

Integrating scrap rubber particles as fillers into polymer matrix composites offers a cost effective and environmentally sustainable pathway to manage tyre waste through the creation of value-added products. This research explores the low-velocity impact (LVI) response and compression after impact (CAI) properties of rubberised foam-core glass fibre-reinforced epoxy (GFRE) sandwich composites. Syntactic foam cores integrated with rubber particles were manufactured using vacuum-assisted resin transfer moulding (VARTM). The compression properties of rubberised foam core, vital for resisting impact damage during LVI, were examined. Results show more than 40% reduction in compression strength and modulus of the syntactic foam upon the inclusion of 33 wt.% rubber particles. The LVI response and residual compression properties of rubberised foam-core composites were also evaluated. Rubberised foam cores caused a marginal reduction in the peak impact force and led to approximately 60% reduction in the delamination area. The pre-impact compression strength was unaffected by rubber particles within the core as the GFRE face sheets carried most of the compression load. Post-impact compression strength was slightly higher in rubberised foam-core composites due to reduced delamination. Digital Image Correlation (DIC) analysis tracking of the strain evolution during CAI experiments revealed the stress-raising effect of the impact damaged region. This study showcases sustainable scrap tyre management through the inclusion of rubber particles into foam-core composites without substantially reducing in-plane compression properties before or after low-velocity impact.

Enhancing wear resistance, mechanical properties of composite materials through sisal and glass fiber reinforcement with epoxy resin and graphite filler

This study investigates the mechanical and wears properties of sisal and glass fiber-reinforced epoxy composites with graphite as filler material. We assessed the mechanical properties of the hand-layup-fabricated composite materials, including hardness, tensile strength, flexural strength, and impact strength, by ASTM standards. We also performed wear evaluations using a pin-on-disc apparatus. The results showed that the weight fractions of sisal fiber, glass fiber, graphite, and epoxy resin significantly affected the mechanical properties of the composites. In contrast to composites reinforced with individual fibers, hybrid composites exhibited enhanced mechanical properties. The optimized compositions showed improvements in tensile, flexural, impact, and hardness properties. The wear analysis revealed that a variety of factors, including the weight percentage of reinforcement, sliding velocity, load, and sliding distance, had an impact on the composites' wear resistance. The SEM images provided significant insights into the composite material's micro structural characteristics and failure mechanisms. In general, this research showcases the potential of graphite filler-reinforced sisal and glass fiber epoxy composites for use in applications that demand exceptional abrasion resistance and mechanical strength. Further refinement of the composition and processing methodologies could lead to the development of composites tailored to specific application demands.

Pyrolysis process and products characteristics of glass fiber reinforced epoxy resin from waste wind turbine blades

The installed wind power capacity has reached up to 906 GW globally meaning the usage of wind turbine blades (WTBs) with around 9.06 Mt. The waste WTBs with a rapid growth was estimated to be 72.0 kt in 2022 based on the projected lifetime of 20 years. The recycling of fibers reinforced thermoset polymer from waste WTBs has become a knotty environmental issue. This work aimed at studying the pyrolysis behaviors of a glass fibers reinforced epoxy resin materials from a waste WTBs, and revealing the impacts of pyrolysis atmosphere and temperature on the pyrolysis products. It was found that the black glass fibers with deposited carbon and the clean glass fibers were obtained by pyrolysis in N2 and air, respectively. Both pyrolysis in N2 and air produced the pyrolysis oil and gas with similar compositions. The preferable strength of fibers and yield of oil could be obtained at applicable pyrolysis temperature of 450 °C. The oil yields were 13.17 wt.-% and 11.93 wt.-% by pyrolyzing at 450 °C in N2 and air, respectively. The analysis of pyrolysis pathway suggested that the oxygen promoted the decomposition of epoxy resin into small molecules of gases by pyrolysis in air. The utilization of recycled products gas was also discussed. The findings of this work could provide some suggestions to explore a route with low cost to recycling the waste WTBs by pyrolysis.

Effect of Flame Retardant Additives on the Flammability and Flame Spread Rate of Glass-Fiber-Reinforced Epoxy Resin with Varying Binder Content: An Experimental and Numerical Study

ABSTRACT This paper presents a study of flammability and downward flame spread rate in an opposed oxidizer flow over glass fiber-reinforced epoxy resin (GFRER) with the added flame retardants 6,6′-((methylenebis(4,1-phenylene))bis(azanediyl)) bis(6 H-dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (DDM-DOPO) and graphene and with a binder content (BC) of ~ 35 wt% and ~ 52 wt%; the mass ratio of the glass fiber to the binder in the composite was 2:1 and 1:1, respectively. To evaluate the flammability and thermal stability of the obtained materials, the LOI test, the UL-94HB test, and thermogravimetric analysis were conducted. The effective DDM-DOPO concentration for decreasing the flammability of GFRER was found based on the LOI results. During the flame spread experiment with an opposed oxidizer flow, the addition of flame retardants resulted in an increase in the limiting oxygen concentration (LOC). Oxygen concentration increase in the oxidizer flow led to a decrease in the flame retardant effect on the rate of flame spread (ROS) for samples with a BC of ~ 35 wt%. The flame retardant effectiveness for samples with a BC of ~ 52 wt% remained almost the same at 40–60 vol% O2 concentrations. The relationship among the LOI, LOC, and ROS was experimentally established. A numerical simulation of flame spread over reinforced material was performed using a coupled gas-solid heat and mass transfer model to predict the ROS over GFRER with and without flame retardants. The model correctly predicted the ROS for GFRER with ~ 35 wt% BC, while for samples with ~ 52 wt% BC, the model gave lower ROS compared to experiment.

Flame-Retardant Glass Fiber-Reinforced Epoxy Resins with Phosphorus-Containing Bio-Based Benzoxazines and Graphene.

This paper presents a study of the flammability and thermal decomposition products of glass fiber-reinforced epoxy resin (GFRER) with the addition of cardanol-based phosphorus-containing benzoxazine monomer (CBz) and graphene and their combinations in different proportions (up to 20 wt.%). The addition of CBz alone or in combination with graphene resulted in an increase in the limiting oxygen index (LOI) and self-extinguishing in the UL-94 HB test. The flame-retardant samples had better tensile mechanical properties than the sample without additives. The differential mass-spectrometric thermal analysis (DMSTA) of the thermal decomposition products of GFRER without additives and with the addition of CBz and graphene was carried out. CBz addition promoted the thermal decomposition of high-molecular-weight products of epoxy resin decomposition in the condensed phase and at the same time decreased the time of release of low-molecular-weight thermal decomposition products into the gas phase. Graphene addition resulted in an increase in the relative intensities of high-molecular-mass peaks compared to GFRER without additives.

Improving tensile properties of glass fiber-reinforced epoxy resin composites based on enhanced multiphase structure: The modification of resin systems and glass fibers

Glass fiber-reinforced polymer (GFRP) composites have been widely used as reinforced materials in marine engineering due to their good corrosion resistance and economic benefits. However, the mechanical properties of GFRP are lower than that of composites reinforced by carbon and aramid fibers etc. Methods to improve the mechanical properties of GFRP received ongoing attention. GFRP have various mechanical properties due to the characteristics of its multiple phases. This study developed an optimized processing method based on multiphase structures for GFRP composites, significantly enhancing the tensile properties of GFRP laminates. The modified GFRP can be produced efficiently by this method to meet more utilization situations in marine engineering. The influence of curing agents, silane coupling agents (SCA)-treated glass fibers (GFs), and nanomaterials on GFRP's tensile properties was investigated. The findings reveal a 10.64 % increase in the characteristic load of GF bundles due to the improved bonding between fibers by SCA. Besides, the contact angle between SCA-treated GFs and epoxy resin shows a significant reduction (26.69 %). Variations in ply thickness and resin system distinctly influence the tensile properties and failure modes of GFRP laminates. Laminates with 4-ply GF fabrics facilitate more effective load transfer across the matrix-fiber boundary, yielding optimal tensile properties for GFRP. Epoxy/phenolic amine resin system with more reactive functional groups (-OH) enhances the fiber-resin bonding, further improving the tensile properties of GFRP. The enhancement mechanism of the multiphase structure in GFRP was elucidated by microscale characterization, indicating that the multiphase structures in GFRP, enhanced by SCA, nanomaterials, and functional curing agents, significantly improve its tensile properties.

Experimental Design and Analysis of MWCNT, Nanoclay and Zinc Oxide Nanofillers on Bi-directional-Chopped Stranded Glass Fibre Reinforced Epoxy matrix on Mechanical Properties using Multi Response Performance Index Approach

Experimental Design and Analysis of MWCNT, Nanoclay and Zinc Oxide Nanofillers on Bi-directional-Chopped Stranded Glass Fibre Reinforced Epoxy matrix on Mechanical Properties using Multi Response Performance Index Approach

Investigation of Drilling Performances, Tribological and Mechanical Behaviors of GFRC Filled with B4C and Gr

AbstractIn this study, the effects of Gr and B4C filler materials on drilling performance, mechanical, and tribological behaviors of glass fiber-reinforced epoxy composites were experimentally investigated. Glass fiber-reinforced composite materials filled with B4C and Gr at different weight ratios (5%, 10%, and 15%) were manufactured using hand lay-up method. The produced composite materials underwent various tests, including mechanical tests (tensile and flexural tests), tribological tests (wear behavior), and drilling tests under different parameters. Additionally, SEM images of the worn and fractured surfaces were examined. The addition of both B4C and Gr fillers adversely affected the mechanical properties of glass fiber-reinforced composites. It was observed that tensile and flexural strengths decreased with increasing filler ratios. However, the addition of B4C and Gr fillers enhanced the wear resistance of glass fiber-reinforced composites. It was revealed that in drilling operations, as the feed rate increased, the thrust forces increased, while the cutting speed increased, the thrust forces decreased. It was determined that delamination values in glass fiber reinforced composites decreased as the feed rate increase, while delamination values increased as the cutting speed increased. Generally, the thrust forces, vibration, delamination, and moment values obtained during the drilling of B4C-filled glass fiber composites were found to be higher compared to Gr-filled glass fiber composites.

Examining thermogravimetric response and morphological alterations in epoxy composites with hybrid ceramic fillers integration

The investigation explores thermogravimetric (DTA/(mW/mg) and TG%) analysis and morphological traits of glass fibre-reinforced epoxy polymer matrix composites (GFRP) incorporating ball-milled ceramic fillers. ZrSiO4, TiO2, FeTiO3, and SiO2 fillers, at varying weight proportions (0:0, 2.5:2.5, 5:5 and 7.5:7.5 wt %) are blended with epoxy using liquid ultrasonication and compression molding to make composites. Ceramic fillers expedite onset of thermal degradation, elevate DTG peak temperature and enhance thermal stability compared to plain GFRP. The composites exhibit significant weight loss between 341.1 °C and 348.4 °C. Epoxy/E-glass fibre composite with 5:5 wt % fillers demonstrates superior thermal and structural characteristics compared to pristine sample.

Effects of Boric Acid on Laminated Composites: An Experimental Study.

In this study, the effect of boric acid (H3BO3) on fiber-reinforced layered composites was investigated. Glass fiber-reinforced epoxy composites were used, and the effects of boric acid on thermal and mechanical properties were investigated. For this purpose, composite plates were manufactured by adding boric acid (BA) to the epoxy in different ratios (0, 0.5, 1, and 1.5% by weight). Tensile tests, compression tests, and shear tests were performed to determine the mechanical properties of these plates, and DSC, TGA, and DMA analyses were performed to determine their thermal properties. SEM and EDS analyses were performed on the specimens to examine their morphologies. Furthermore, examinations were conducted on how BA affected the specimens' failure behavior. In the study, it was found that, except for the compressive strength, the mechanical properties were improved by the added BA. The highest tensile strength, shear strength, modulus of elasticity, shear modulus, and Poisson's ratio were obtained from 0.5% BA-added specimens and were 24.78%, 8.75%, 25.13%, 11.24%, and 12.5% higher than the values obtained from 0% BA-added specimens, respectively. The highest loss and storage modulus were obtained from 0% and 0.5% BA-added specimens, respectively. The specimens' glass transition temperatures were decreased by the addition of BA; the specimen with a 1% addition of BA had the lowest value. Furthermore, interlayer delamination and fiber/matrix failure were observed in all BA-added specimens.

The noteworthy tensile plasticity and strength of CoFeSiB metallic glass fiber reinforced epoxy composites

AbstractMetallic glass fibers have high strength, poor plasticity and low Young's modulus. In this study, it was used as a reinforcement to prepare metallic glass fiber reinforced epoxy composites with different fiber volume contents (20%, 30%, 40%, and 50%). The effect of fiber volume contents on the tensile properties of the metallic glass fiber reinforced epoxy composites was studied by experiment and the finite element analysis method. The experiment and simulation results are in good agreement. The tensile strength and plasticity of the metallic glass fiber reinforced epoxy composites increase with the increase of fiber volume contents. When the fiber volume content is 40% or 50%, a sharply necking feature appeared on the fibers and exhibited improved plasticity, due to the formation of interacting and arresting events of shear bands occurring at the interface between the metallic glass fibers and the epoxy. In addition, the strain hardening due to plastic deformation of the metallic glass fibers further enhanced the tensile strength of the metallic glass fiber reinforced epoxy composites. This is a first step toward toughening the inherently brittle metallic glass fibers under tensile conditions.Highlights A novel CoFeSiB metallic glass fiber reinforced epoxy resin composite The increase of fiber volume fraction improves the tensile strength and plasticity of fiber reinforced composites. The strain hardening due to plastic deformation of the metallic glass fibers further enhanced the tensile strength of the metallic glass fiber reinforced epoxy composites.

Partnerships Crucial in Developing Nonmetallic Downhole Tubulars

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 23491, “Role of Ecosystem Partners To Make Nonmetallic Downhole Tubulars a Reality,” by Ahmed Aladawy, SPE, and Ameen Malkawi, SPE, Baker Hughes, and Omar El Shamy, SPE, Novel Non-Metallic Solutions. The paper has not been peer reviewed. Copyright 2024 International Petroleum Technology Conference. _ Nonmetallic (NM) downhole tubulars offer a longer lifetime than their steel counterparts while eliminating corrosion concerns and lowering total cost of ownership. Making them a reality, however, requires a rigorous ecosystem with multidisciplinary skill sets and technology expertise. The complete paper discusses the challenges that face the development of such tubulars starting from academia and research institutes to complement expertise and computer computational power and moving through to material suppliers and manufacturing facilities for pipe prototyping. NM Pipe Construction and Technology Status NM pipes also can include metallic elements, where a hybrid system of NM layers is incorporated into multilayered pipe structures that assume specific roles, similar to a metallic pressure armor layer in subsea flexible risers, jumpers, and flowlines. Another example is polymer-lined steel rigid pipes with glass-fiber reinforced epoxy (GRE), or a dual-layer thermoplastic-lined reinforced pipe (Fig. 1). Composite-based NM pipes can broadly be categorized into reinforced thermoplastic pipe (RTP) and reinforced thermoset pipe (RTR), with glass-fiber reinforced plastic pipe (GRP) and GRE considered a subset of RTR. RTP consists of thermoplastic matrices and layers that can soften after heating and can harden when cooled in a reversible process, thus having the potential to recycle. Because of the flexibility of thermoplastic polymer, RTP pipes up to hundreds of meters long can be spooled on reels and deployed through rigless operation, with reduced system cost and deployment time. This synopsis will concentrate, as does the complete paper, on RTP. RTP pipe design can be classified as unbonded, semibonded, or fully bonded. Essentially, three layers of constituents for RTP exist: the inner layer is a fluid barrier (liner), the second layer is a load-bearing component (reinforcement), and the outer layer is external protection (cover). Unbonded RTP pipe means that the layers are not heat-fused to one another during manufacturing and are free to move between layers. This type of RTP pipe usually is low to medium in pressure rating, especially with regard to collapse rating, but also is lower in manufacturing cost and is suitable in onshore applications for fluid transportation. To increase the pressure rating, semibonded RTP pipes can be considered if pipe thickness is a limitation. For offshore and downhole applications, however, where higher pressure and temperature ratings are required, fully bonded RTP pipes, more commonly known as thermoplastic composite pipes, are preferred to handle high burst and collapse-pressure requirements and more-consistent load transfer across the structure. All RTP types can be manufactured continuously into pipe lengths of hundreds of meters because of their flexibility, but fully bonded RTP may be limited to larger-bend radii than unbonded or semibonded RTP; consequently, a need exists to consider reel-size limitations or even carousels to wind long pipe lengths during manufacturing. Conversely, fully bonded RTP structures may be easier to model and analyze than unbonded pipe.

Assessing the crashworthiness of nanocarbon‐filled glass fiber reinforced epoxy composite tubes under axial loading

AbstractThis research aimed to understand how the incorporation of nanocarbon powder (NCP) influences the crashworthiness performance of glass fiber‐reinforced epoxy (GFRE) tubular components, potentially offering insights into improving the safety and resilience of structures or vehicles. Consequently, the crashworthiness behaviors of circular tubes made of GFRE with varying amounts of NCP was studied. Utilizing wet‐wrapping through hand lay‐up technique, GFRE tubes were fabricated with various weight percentages of NCP, that is, 0, 0.25, 0.50, 1, 2, 3, and 4 wt.%. Following that, the crashing load, total absorbed energy against displacement responses, and deformation histories of these tubes under quasi‐static axial loading conditions were calculated and tracked. As part of the crashworthiness analysis, critical indicators were evaluated, including initial peak load (), total absorbed energy (U), mean crash force (), crash force efficiency (CFE), and specific energy absorption (SEA). The findings reveal that the maximum , U, , and SEA were noted at 0.5 wt.% of NCP, with increasing percent's of 30.80, 12.17, 12.16, and 7.50, respectively, compared to the unfilled tube. While, the CFE was recorded by 3 wt.% of NCP with an enhancement of 16.67%. It is worth to note that, the findings reveal that the inclusion of NCP increases crashworthiness metrics up, that is, , U, , and SEA to a concentration of 0.50 wt.% NCP. However, beyond this point, there's a notable decline in performance.Highlights The GFRE tubes were filled with various wt.% of NCP. The planned tubes were made using hand lay‐up methods. The tubes were subjected to axial compression loads to examine their crashing behavior. The crashing load and absorbed energy versus displacement responses for tubes were exposed. The experimental results were analyzed and discussed.

Experimental Design and Analysis of MWCNT, Nanoclay and ZnO Nanofillers on Bi-Directional-Chopped Stranded Glass Fibre Reinforced Epoxy Matrix on Mechanical Properties using L9 and L18 Taguchi’s Orthogonal Technique

Stealth, mechanical and thermal properties, resistance to fire by limiting oxygen and retarding flame can lead to save several human lifes travelling and working in civil, commercial as well as defence air transport and could even develop drone and aircraft meant to escape enemy countries radar tracing and monitoring range. GFRP play very important role in engineering application. The composite manufactured using nanofillers have found to posses better propeties in certain application. In the present work, MWCNTs, Nanoclay and ZnO have been used in GFRP. The developed material can be a promising replacement of composites being used for structural applications in the aerospace sector and space technology apart from the automotives to impart light weight, superior bending and tensile strength. Testing of GFRP infused nanofillers was conducted to obtain the ultimate tensile strength and flexural bending strength of the composite. Experimental design with three Nanofillers as parameters at three levels for optimization of output characteristics with superior properties for structural applications was done using Taguchi’s L9 and L18 orthogonal arrays. ANOVA Analysis was also performed for both L9 and L18 arrays. The effects of three nanofillers infused GFRP was investigated and their impact on tensile and flexural strength were evaluated.

Atmospheric plasma treatment effect on shear strength of GFRP-Aluminum adhesively bonded lap joints

The objective of this study is to investigate the effect of air (dielectric barrier discharge) DBD plasma treatment on the bonding strength of adhesively bonded glass fiber-reinforced epoxy composite-aluminum lap joints. The bonding performance of lap joints produced by the plasma treatment was compared with that of untreated and peel-ply surface treatments. Water contact angles of the substrates were measured for untreated, peel-ply, and plasma surface-treated substrates. Experimental results showed that plasma-treated aluminum and GFRP substrates increased the wettability properties and thus shear strength of adhesively bonded GFRP-Al joints increased. After the shear tests, the fracture surfaces of the substrates were visually examined and three different damage modes were observed, including light fiber tear failure, adhesive failure, and thin layer cohesive failure modes.

High-performance hybrid glass fibre epoxy composites reinforced with amine functionalised graphene oxide for structural applications

Glass fibre-reinforced epoxy (GFRE) composites have had limited use as structural components in industrial applications (e.g., oil and gas, aerospace and civil infrastructure). The use of nanomaterials, such as graphene, has been explored recently to enhance the mechanical and long-term properties of GFRE to realise their full potential and increase their usage. This study evaluated the tensile, creep, and fatigue behaviour of amine-functionalised graphene oxide (fGO) modified glass fibre/epoxy laminate composites. A spray coating technique was used to coat the fGO particles onto the glass fibre surface, and epoxy composite laminates were manufactured using the vacuum resin infusion method. Creep and fatigue testing was performed under a load-controlled mode in tension. Adding fGO within the composites significantly improves the static, creep, and fatigue properties of the fGO-GFRE composites at both room and elevated temperatures. It is shown that fGO acts as a barrier to microcrack initiation and restrains the macrocrack propagation during cyclic loading under elevated temperatures in the GFRE composites. These factors, therefore, prevent the early delamination of the matrix and fibre interface during cyclic loading, which explains the fatigue life extension observed in the fGO-modified composites. With 0.05 wt% fGO, the fatigue life of the fGO-GFRE composites was extended by 8× and 30× at a maximum stress of 124 and 151 MPa respectively, in a 90 °C environment compared to the control GFRE composites. While the creep life compared to the control increased by 63×, 103× and 159× with 0.25 wt%, 0.5 wt% and 1 wt% fGO, respectively. These enhancements are attributed to the large surface area, high stiffness, and functional groups present, which provide a stronger bond between the composite phases. These features help restrict the mobility of the polymer chain during the creeping load and act as barriers to fatigue crack propagation, enhancing the composite’s durability. The nanocomposites produced display attractive properties for many possible industrial applications where improved performance is needed while maintaining a minimum cost.