Vacuum Assisted Resin Infusion Research Articles

Shear strength comparison of single lap and joggle lap adhesive joints in carbon fiber composites manufactured via vacuum-assisted resin infusion

The extensive utilization of composite materials has spurred the advancement of diverse joining techniques suitable for components constructed from such materials. This study focuses on the examination of two specific types of joints: single lap and joggle lap joints. The specimens utilized were composed of unidirectional carbon fiber composite combined with vinyl ester resin, manufactured via the vacuum-assisted resin infusion method. Vinyl ester adhesives were employed in the bonding process, with the joint surfaces undergoing sanding treatment prior to testing. Mechanical testing was conducted on the specimens according to ASTM D5868 standard, employing a constant crosshead speed until failure occurred. The test results reveal that the shear strength of single lap joints surpasses that of joggle lap joints. Within the single lap joint configuration, a mixed failure mode comprising both adhesive and cohesive failure is observed. Conversely, in joggle lap joints, substrate delamination is prevalent, suggesting the predominance of peel stress during loading.

Investigations on the influence of thickness and preform structure on the mechanical performance of novel textile composites with woven Kevlar® fabric reinforcement and poly methylmethacrylate (Elium®) matrix

Abstract Elium (novel methyl methacrylate (MMA)) resin is a liquid thermoplastic resin curable at room temperature and a possible replacement for epoxies. The main objective of this work is to evaluate the mechanical characteristics of novel Kevlar fabric reinforced Elium composites with different thicknesses. The plain-woven structure Kevlar/Elium laminates were manufactured with 1.5 mm and 2.5 mm thicknesses through vacuum-assisted resin infusion moulding, where 8 and 12 layers of woven fabrics were used, respectively. The effect of laminate thickness was measured in terms of mechanical (tensile, flexural, shear, and dynamic mechanical analysis (DMA)) and physical (density and fibre volume fraction (FVF)) characteristics. The density of the laminates was found in the range of 1.18–1.31 g cm−3. FVF was 50.69 and 52.27% for 1.5 and 2.5 mm thick laminates, respectively. The composite with 1.5 mm thickness exhibited the highest tensile strength (667.9 MPa) and flexural strength of 330.7 MPa. Conversely, the highest interlaminar shear strength measured for 2.5 mm thick laminate is 16.5 MPa. The DMA analysis recorded the highest storage and loss modulus for 2.5 mm thickness laminates. The fractography analysis confirmed the quantified experimental observation of excessive interface debonding and delamination. Elium composites may be suitable for high-end structural applications, including marine and aircraft structures.

Self-healable epoxy/graphene oxide vitrimers and their recyclable glass fiber reinforced composites

Glass fiber-reinforced polymers (GFRPs) made from thermoset polymers have been widely used across various industries. However, these composites have significant drawbacks, including poor interfacial adhesion between the fiber and matrix, as well as a substantial contribution to waste and environmental pollution due to the challenges in recycling, reprocessing, and reuse. Herein, firstly graphene oxide (GO) was incorporated in vitrimer matrix to fabricate recyclable vitrimer nanocomposites with improved interfacial interaction, high thermal stability, low dielectric constant, fast stress relaxation as well as rapid self-healing ability. The nanocomposite with 0.2 wt% GO is optimized to achieve excellent remoulding (89% of flexural strength) and self-healing (60 min for a 48 μm scratch) properties due to dynamic disulfide bond exchange mechanism. Furthermore, epoxy/GO matrix was used to develop glass fiber reinforced composites via vacuum assisted resin infusion molding process (VARIM). The developed composites demonstrate tremendous mechanical strength (250 MPa), shape-memory, weldability, and degradable properties. Due to the rapid chemical degradation of epoxy vitrimer under mild conditions in the thiol (2-mercaptoethanol and 1-otanethiol), facilitated by thiol disulfide exchange reaction, glass fibers (GFs) can be effectively recycled. The performance of recycled glass fibers closely matches that of original fibers, exhibiting nearly identical woven structure and mechanical properties. The single yarn of recycled glass fibers can achieve tensile strength of 85% (1-octanethiol) and 72% (2-mercaptoethanol) of the original glass fibers, thus, the recycling of glass fibers would be highly advantageous in terms of achieving the sustainability goals.

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.

Effects of crosslinker concentration on curing process and performances of needled fiber preform reinforced phenolic aerogel composite using process simulation and comprehensive experiments

A kind of needled quartz/carbon fiber preform reinforced phenolic aerogel composite (NQCF/PR) was fabricated through impregnating needled fiber preform with phenolic resin precursor solution, followed by sol–gel polymerization and solvent drying. The needled fiber preform serves as lightweight quasi-three-dimensional reinforcement, while phenolic aerogel matrix provides high porosity and low thermal conductivity. During fabrication of aerogel composite part using vacuum-assisted resin infusion process, distribution of crosslinker hexamethylenetetramine (HMTA) in precursor solution can be problematic, as precipitated crosslinker particles may be filtered by fibrous preform. In this study, the impact of HMTA filtration induced heterogeneous structure on subsequent curing process was investigated using process simulation. Temperature effects of sol–gel polymerization and solvent evaporation were considered through establishment of corresponding kinetic models. Impacts of heterogenous structure on distribution of temperature, resin curing degree and solvent conversion degree in large hemispherical aerogel composite structure were investigated. This leads to variations in gel network and pore structure of aerogel, thereby affecting final material performance. Based on experimental results, as HMTA concentration increases, compressive performance of NQCF/PR obviously increases. Among these, NQCF/PR with 4.7 wt% HMTA provides a balance of lightweight nature (0.25 g/cm3), excellent thermal insulation property (0.052 W·m−1·K−1) and compressive performance (strength of 0.35 MPa).

Research of influence of diluent on the mechanical behavior of triaxial warp-knitted composites

The composites are prepared by different processes of reinforcement and matrix, which are affected by the properties of reinforcement and matrix. In this study, composite specimens were fabricated using vacuum-assisted resin infusion (VARI) with varying mass fractions (0%, 5%, 10%, and 15%) of a diluent mixed with the resin and curing agent, serving as the matrix. Triaxial warp-knitted glass fabric was employed as the reinforcement material. The impact of the diluent mass fraction on the bending, impact, and creep properties of the composites was investigated. The least squares fitting method was applied to analyze the experimental data, leading to the establishment of a mathematical model correlating the diluent mass fraction with the bending strength. The optimal diluent mass fraction for achieving the best bending properties was determined. Furthermore, the failure mechanisms of the composites were examined through an analysis of their thermodynamic properties, reaction principles, and fracture morphologies. The results show that the epoxy group in the diluent will be connected to the cross-linking network structure of epoxy resin by ring-opening reaction, and excessive addition will lead to the increase of flexible chain segments, which makes the mechanical properties of the specimens increase first and then decrease. The mathematical model was verified by experiments, and the mass fraction of diluent was 9.65% when the bending property was optimal.

Failure mode maps for glass fibre-reinforced polymer/polyvinyl chloride foam-cored sandwich structures

Purpose This study aims to understand how the facesheet size, orientation and core size influence the analytical failure mechanism mode of glass fibre reinforced polymer (GFRP)/polyvinyl chloride (PVC) sandwich structures subjected to three-point bending. The purpose of this study was to develop failure-mode map of GFRP/PVC sandwich structures. Sandwich structures with different facesheet and core thicknesses were used to develop the failure map. Design/methodology/approach The sandwich structure and facesheet were fabricated using a vacuum-assisted resin infusion method with core sizes of 10, 15 and 20 mm and facesheet thicknesses of 1.5 and 3 mm and were arranged in three different orientations: angle-ply, cross-ply and quasi-isotropic. The key failure modes that occur in sandwich structures were used to predict possible failures in the developed material. Analytical equations were used in MATLAB for each observed failure mode. The probable failure modes, namely, face yielding, core shear and indentation equations, were used to construct the failure maps and were compared with the experimental data. Findings The boundary of the two failure modes shifts with changes in the facesheet and core thicknesses. The theoretical stiffness of sandwich panels was higher than the experimental stiffness. Based on strength-to-weight ratio, specimens E10-4, A15-8 and E20-8 exhibited the best optimum values owing to their shorter distance to the boundary lines. Originality/value In this study, a failure map was used to predict the possible failure modes for different GFRP facesheet orientations and thicknesses and PVC core thickness sandwich structures. Little is known about the prediction of the failure modes of unidirectional GFRP arranged in different orientations and thicknesses and PVC core thicknesses for sandwich structures. Few studies have used failure mode maps with unidirectional GFRP oriented in angle-ply, cross-ply and quasi-isotropic directions as a facesheet for sandwich structures compared to bidirectional mats. This study can serve as a guide for the correct selection of materials during the design process of sandwich structures.

Effect of halloysite addition on the dynamic mechanical and tribological properties of carbon and glass fiber reinforced hybrid composites

Composite materials have become prominent in the aerospace, automotive, wind energy, biomedical, and machine tool industries. This has demanded the evaluation of the dynamic mechanical and tribological behaviour of composites to understand their performance and ensure their reliability and safety in varied operating conditions. In this study, the effect of halloysite nano-clay addition on the dynamic mechanical and tribological properties of the carbon/glass hybrid composites was investigated. The composites were produced with the vacuum assisted resin infusion process. by varying the content of halloysite nano-clay (1, 3, and 5 wt%). The dynamic mechanical properties of the manufactured composites were examined at temperatures ranging from 30 °C to 180 °C. The tribological properties of the specimens were assessed by varying the applied load (10, 20, and 30 N), sliding speed (1.5, 3, and 4.5 m/s) and sliding distance (500, 1000, and 1500 m). Box-Behnken design was utilized to optimize the number of experiments. The results showed that the halloysite-added samples had better dynamic mechanical and tribological properties than the carbon/glass hybrid composites. Especially, hybrid composites containing 3 wt% halloysite outperformed the other composites investigated. A scanning electron microscope (SEM) was used to examine the worn surface and wreckage in the investigated composite specimens.

Comparison of carbon‐reinforced composites manufactured by vacuum assisted resin infusion with traditional and fully recyclable epoxy resins

AbstractThis study presents a comparative analysis of carbon fiber reinforced polymer (CFRP) composites manufactured through vacuum assisted resin infusion (VARI) using a traditional epoxy resin (E), a fully‐recyclable epoxy resin system with (BBR10) and without (BBR) the addition of a reactive diluent (R*Diluent). Various mechanical and thermal tests were conducted to assess their performance. The BBR10 laminate, incorporating 10 wt% R*Diluent, exhibited competitive mechanical performance, comparable to traditional (E) and fully‐recyclable laminates (BBR). Despite a slightly lower ultimate tensile strength (UTS) compared with BBR, BBR10 demonstrated improved flexural strength and modulus. Low‐velocity impact testing confirmed comparable strength between VARI‐produced composites with the recyclable matrix (BBR and BBR10) and the traditional one (E). X‐ray mCT investigations revealed distinct void arrangements in the CFRP laminates. Additionally, a chemical approach was employed for recovering high fractions of fibers from CFRP laminates with a recyclable matrix (BBR and BBR10). Chemical recycling achieved an almost 100% yield for long carbon fibers.Highlights Comparative analysis of CFRP composites manufactured through VARI. Diluent addition allowed to tailor the recyclable epoxy viscosity. Mechanical characterization of traditional and fully recyclable epoxy resins. Investigation by X‐ray mCT of potential flaws and manufacturing defects. Chemical recycling of CFRP laminates with a recyclable matrix.

Development of New Lignin-Based Coatings with Ultraviolet Resistance for Biobased Composite Materials.

Nowadays, there is a challenge in searching for more sustainable alternatives to decrease the environmental impact of composite materials. In this work, we fabricate new composites based on a biobased-content epoxy system, lignin, and flax fiber; considering these materials could be promising due to their high renewable content of around 40%. In addition, another key requirement for composites, besides being sustainable, is that they present improved properties such as UV resistance. Therefore, throughout this work, priority was given to improving UV resistance in addition to taking into account sustainability. In order to carry out a complete characterization of the materials developed, the mechanical properties, brightness, and thermal, rheological, and fire behavior of these kinds of materials were analyzed by using vacuum-assisted resin infusion processes. By way of conclusion, it should be noted that the manufactured composite with the optimized formulation showed improved UV resistance using lignin and that it could be applied on internal and external walls according to the railway fire regulations.

Effect of MWCNTs on static, dynamic, and wear performance of Vacuum Assisted Resin Infusion Molding (VARIM) processed glass fabric/epoxy polymer composites

In the present work, MWCNTs were used in wt.% of 0.075, 0.15, and 0.3 in epoxy resin, and then glass fabric/epoxy polymer (GF/EP) composites were fabricated using VARIM setup. The mechanical and wear properties of GF/EP composites were compared with and without the addition of MWCNTs. Maximum improvement in tensile and flexural performance were seen in GF/EP composites at 0.15 weight percent MWCNT addition when compared to a neat GF/EP one, based on static testing such as tensile and flexural tests. High-cycle fatigue test results show a relatively higher cycle count with 0.15 wt.% MWCNTs addition in the GF/EP composite compared to the GF/EP without the addition of MWCNTs. The wear performance also improved with a lower friction coefficient as well as a lower track depth and width for MWCNTs with added GF/EP than plain GF/EP composite. Therefore, in addition to decreasing surface softening and improving the wear performance of glass fabric epoxy composites, MWCNTs (0.15 weight percent) increased the interfacial adhesion at the fiber/matrix interface. This study establishes an optimum ratio of 0.15 wt.% of MWCNTs addition in glass fabric/epoxy polymer composites for enhancement in their mechanical and wear performance.

Mechanical properties of glass/epoxy composites under artificial seawater environment: Numerical simulation and experimental validation

In ocean engineering applications, glass fiber reinforced composite materials undergo degradation over time due to various aging processes. Accurately assessing the mechanical properties of these materials as they experience aging conditions in marine environment becomes a crucial factor. Although various approaches, such as experimental, theoretical, or finite element methods (FEM), have been employed to investigate the impact of aging processes on composite materials, limited attention has been given to examining the damage of composite plates under the exposure of artificial seawater environments using the MAT162 material model. The objective of this study is to outline a methodology for identifying a group of MAT162 parameters in LS-DYNA through a unit single element analysis. S2 glass/epoxy composites were produced by vacuum assisted resin infusion method. Aging was carried out in artificial seawater environment for 4, 8 and 12 months. Tensile, through thickness tensile, compression, through thickness compression tests were performed and then the finite element modeling was conducted. Maximum strength (X1T, X1C, X3T and SFC), element eroding axial strain (E_LIMT), modulus of elasticity (E1 = E2, E3), scale factor for residual compressive strength (SFFC), coefficient for strain softening property (AM) parameters were analyzed. It was determined that the proposed model for aging was in good agreement with the experimental study.

Interlaminar toughening of carbon fiber/epoxy composites via interleaving co‐polyamide (Co‐PA) veils

AbstractThermoplastic veil interlayers offer a promising approach to improve interlaminar reinforcement in composite materials. This study investigates co‐polyamide (Co‐PA) interleaved veils, fabricated through the hot melt adhesive (HMA) technique. These veils are then applied with varying areal weight densities as interleaves to simultaneously toughen and strengthen carbon fiber/epoxy (CF/EP) composites, utilizing the vacuum‐assisted resin infusion (VARI) method. Integrating Co‐PA veils with a low melting point in the interlaminar of CF/EP composites improves compatibility and promotes strong adhesion between thermoplastics and epoxy resins. As result, The Co‐PA laminates exhibited significant improvements compared with the untoughened composites, with a maximum enhancement of 148.1% and 67.8% for Mode‐I (GIC) and Mode‐II (GIIC), respectively. Moreover, ILSS, tensile strength, and flexural strength improvements were also 20.9%, 34.9%, and 14.5%, respectively. The fracture surface analysis via scanning electron microscopy directly revealed the crack propagation on the fracture surfaces of Mode‐I and Mode‐II specimens. This analysis revealed that Co‐PA demonstrated excellent compatibility with epoxy resin, melts during the stage of epoxy curing, and undergoes phase separation in the later stage, resulting in the formation of “bead‐like” structures within the fibrous network. Remarkably, this structure significantly enhanced the toughness of the CF/EP composites. The Co‐PA veils can improve the interlaminar toughness of CF/EP composites due to their compatibility with the epoxy matrix and high inherent toughness and strength. This method is straightforward to manage and can be utilized for manufacturing large‐scale composite materials incorporating CF fabrics, demonstrating promise for industrial applications.Highlights With its low melting point, co‐polyamide helps prevent structural failure or excessive damage and is proposed to be utilized in composites to enhance the interlaminar fracture toughness properties. The effects of Co‐PA veils of different areal densities on the mechanical characteristics of interlaminar composites were examined. Co‐polyamide particles with fiber‐carbon laminates offer superior fatigue properties and an optimum carbon fiber‐bridging mechanism. Co‐polyamide veils with CF/EP laminates are feasible for structural use in high‐tech automotive applications.

Improved Mechanical Properties of Graphene/Carbon Fiber Composites via Silanization.

Despite their excellent mechanical performance, carbon fiber-reinforced polymer (CFRP) composites are limited by the interfacial properties due to the inherent nature of laminated structures. One way to modify the interface is by the inclusion of nanomaterials. Here, we use electrochemical exfoliation to produce graphene (EEG) flakes that have hydroxyl and epoxy functional groups. To further improve the interfacial bonding, silanization was carried out on graphene with 3-aminopropyl triethoxysilane, and then, EEA flakes were achieved. Both flakes were dispersed in ethanol and spray-coated onto carbon fibers, followed by vacuum-assisted resin infusion to make hybrid composites. Testing of their mechanical properties showed that EEG flakes tend to act as points of stress concentration, which accelerated the delamination, while the EEA flakes improved interfacial properties owing to the covalent bonding. As a result, with only 0.5 wt % EEA flakes spray-coated onto the carbon fibers, the tensile and flexural strength of graphene/carbon fiber composites improved by 17.6 and 5.4%, respectively. The combination of electrochemical exfoliation, silanization, spray coating, and vacuum-assisted resin infusion enables large-scale hybrid composite fabrication without size or shape limitations, without weakening the CFs or carbon fabric patterns, and is suitable for continuous production. This process has proven to be practical and attractive for engineering applications.

Mechanical and viscoelastic properties of novel resin-infused thermoplastic tri-block copolymer 3D glass fabric composites

The current study investigates the mechanical and viscoelastic properties of a novel acrylic resin-infused thermoplastic (Elium®) tri-block copolymer (Nanostrength®) 3D fibre-reinforced composites (FRCs). The toughened thermoplastic resins with three different concentrations of tri-block copolymer, i.e., 10 wt%, 15 wt%, and 20 wt%, were prepared and used to fabricate thermoplastic 3D-FRCs using a vacuum-assisted resin-infusion process at room temperature. The flexural, interlaminar, and viscoelastic properties and failure modes were evaluated and compared with those of pristine thermoplastic 3D-FRCs. The addition of tri-block copolymer significantly improves the flexural strength of 3D-FRC (up to 75 % and 34 % along the warp and fill directions, respectively, at 15 wt% of tri-block copolymer) and interlaminar shear strength (up to 80 % and 111 % along the warp and fill directions, respectively, at 20 wt% of tri-block copolymer). Additionally, the residual flexure and interlaminar shear strength improved up to 35 % and 109 % at 15 wt% of tri-block copolymer. Dynamic mechanical analysis (DMA) demonstrated that the glass transition temperature and storage modulus of thermoplastic 3D-FRCs were increased up to 11 °C and 24 %, respectively at 20 wt% of tri-block copolymer, which may be due to increased physical crosslinking and the agglomeration of tri-block copolymer particles. The improved mechanical and viscoelastic properties of resin-infused thermoplastic tri-block copolymer 3D-FRCs are attributed to better interface adhesion, improved matrix toughness, and crack-bridging mechanisms induced by the tri-block copolymer. The toughened thermoplastic 3D-FRCs can be utilized in the design and development of composite structures for improved damage tolerance applications.

MODIFICATION OF WOVEN DENDROCALAMUS ASPER IN COMPOSITE APPLICATIONS

The aim of this study is to examine the influence of immersing Petung Bamboo in a NaOH solution on the tensile strength (TS) of composites containing an epoxy matrix. Petung Bamboo Webbing was given 0%, 3%, 6% and 9%, soaking treatment. The Composite utilised in this investigation was fabricated by the Vacuum Assisted Resin Infusion technique. Tensile testing of composites is conducted according to the ASTM D638-1 standard. The findings indicated a positive correlation between the concentration of NaOH immersion and the adhesion between the woven surface of Petung Bamboo and the matrix. Consequently, the TS of the Composite was enhanced. However, increasing the concentrations beyond a certain point leads to more degradation of the lignin and cellulose in the fibers, resulting in a loss in the strength of the composite. The Petung Bamboo woven reinforced Composite achieved the highest TS of 136.06 MPa after being treated with a 6% NaOH immersion. This was followed by a 3% NaOH immersion treatment resulting in a TS of 106.04 MPa. Without any NaOH immersion treatment, the composite had a TS of 97.31 MPa. The lowest TS of the composite was observed after a 9% NaOH immersion treatment, measuring 90.79 MPa. The Petung Bamboo wicker-reinforced composite with NaOH immersion treatment showed higher fiber pullout and fiber-matrix debonding failures, while higher NaOH treatment concentration reduced these failures.

Mechanical Behaviour of Glass Fibre-Reinforced Polymer/Polyvinyl Chloride Foam Cored Sandwich Structures

This study focuses on the fabrication and analysis of the mechanical behaviour of unidirectional (UD) glass fibre-reinforced polymer (GFRP) facesheet and polyvinyl chloride (PVC) foam core sandwich structures fabricated by a vacuum-assisted resin infusion method (VARIM). These sandwich structures are commonly used in marine and wind turbine blade applications. To date, relatively little knowledge about the functional behaviour of UD GFRP compared to composites reinforced with bidirectional mats is available for day-to-day applications. The effects of the facesheet orientation, facesheet thickness, and core thickness on the mechanical behaviour of the specimens were examined. The UD fibres were oriented in cross-ply (0/90), angle-ply (+45/−45), and quasi-isotropic orientations. Various mechanical properties such as tensile, flexural, flatwise compression, and edgewise compression tests were examined. Characterization of the tensile properties of the facesheet showed that the cross-ply orientation had a higher strength than the angle-ply and quasi-isotropic orientations. The flexural load-carrying capacity of the cross-ply facesheet orientation was superior to the other orientations. The increase in the core thickness changed the flexural failure mode from face yield and core shear to core indentation. Flatwise compression (FWC) was tested to determine the core characteristics of the sandwich structure, and the peak loads of 4.90, 1.81, and 3.90 kN were obtained for 10-, 15-, and 20 mm core thicknesses, respectively. Edgewise compression (EWC) exhibited stable end crushing for thinner facesheet, whereas thicker facesheet showed core crushing and buckling. When the facesheet thickness was increased from 1.5 mm to 3 mm in the EWC, the buckling load increase ranged from 2.53% to 44.83% for core thicknesses 10-, 15-, and 20 mm, respectively.

Experimental investigation on damage mechanism of GFRP laminates embedded with/without steel wire mesh under low-velocity-impact and post-impact tensile loading

Abstract To investigate the impact behavior and residual strength of glass fiber-reinforced polymer (GFRP) laminates embedded with/without steel wire mesh, low-velocity-impact (LVI) and post-impact tensile tests are conducted carefully. According to the wire diameter and spacing of steel wire mesh, we manufactured two groups of specimens via conventional vacuum-assisted resin infusion. Further, the digital image correlation technique was applied to record the strain evolution. Based on the results, including impact response history, failure morphology, strain contour, the failure mechanism and effect of the parameters of steel wire mesh is revealed in detail. The results show that the embedding of wire mesh can improve the impact resistance and residual strength, with a more significant effect as both the increase of wire diameter and decrease of wire spacing. Compared with GFRP laminates, the peak force of specimens with the thickest and densest wire mesh increase by 105% and 141% under LVI tests and 254% and 141% in post-impact tensile tests, respectively.

EXPERIMENTAL ANALYSIS OF THE EFFECT OF THE WOVEN ARAMID FABRIC ON THE STRAIN TO FAILURE BEHAVIOR OF PLAIN WEAVED CARBON/ARAMID HYBRID LAMINATES

Remarkable advances in the research and development of micro/mini Unmanned Aerial Vehicles (UAVs) seek thin, lightweight and strong materials for their structural applications. As these structures involve various loading conditions in both the in-plane and through-the-thickness directions during their life cycle, the assurance of the structural stability in each direction is deemed mandatory. The woven Aramid fibers as high strain materials (HSM) are known to improve the through-the-thickness impact strength. However, the addition of the HSM can affect the overall tensile behavior of composite laminates. This study investigates the effect of the woven Aramid fiber on the in-plane tensile behavior of Carbon/ epoxy laminates. Laminates are fabricated using an easy and cost-effective Vacuum Assisted Resin Infusion Molding (VARIM) setup. A uniaxial tensile test was conducted to analyze the tensile behavior of Carbon/Aramid hybrid composites. The effect of adding the woven Aramid layer and the Carbon fabric sequence on the tensile modulus, strain to failure and modulus of toughness are investigated in this study. The results revealed that the presence of Aramid has a positive hybrid effect on the failure strain, exhibiting pseudo-ductile behavior with a compromise in the tensile modulus of the virgin Carbon/epoxy laminate.

Study on impact properties of carbon/kevlar fiber hybrid composites

AbstractIn this article, carbon/kevlar hybrid composites were prepared using Vacuum Assisted Resin Infusion (VARI). The sandwich structure with plain carbon weave fabric as the core layer and plain kevlar weave fabric as the surface layer was selected as reinforcement and the solution of epoxy resin and curing agent was selected as matrix. The low velocity impact experiment and compression after impact (CAI) experiment were carried out on the samples at different hybrid ratio and different temperatures, and the mechanical response on the impact loads were analyzed respectively. The results show that the specimen can limit the delamination defect expansion of the surface kevlar fiber as the carbon fiber used as the core layer, which reduce the delamination defect area and improve the impact resistance of the sample. The toughness of the sample improves the brittle failure mode, that is, the sample still has a certain bearing capacity after the load exceeds the maximum strength, the sandwiched composites presents a positive hybrid effect. With the increase of temperature, the matrix was obviously softened, the macromolecular movement in the system was intensified, the three‐dimensional network macromolecular structure of the matrix and the fiber/matrix interface properties were damaged, and the mechanical properties showed an obvious downward trend. As far as the influences of hybrid ratio and temperature on impact behavior of composite are concerned, it lay a theoretical foundation for the industrial application of carbon/kevlar hybrid composites.Highlights The sandwiched structure was used to design the composites, which greatly improves the impact properties of the specimens. The impact properties and compression after impact properties at different hybrid ratios and different temperatures were studied. Based on the hybrid effect and temperature effect, the impact failure mechanism of the sample was analyzed.