Carbon Plies Research Articles

Behaviour of hybrid fibre reinforced polymer (HyFRP) laminates on high strength concrete (HSC) beams under flexural loading

In this paper, experimental studies of hybrid fibre reinforced polymer (HyFRP) laminates consisting of carbon ply fibre reinforced polymer (CFRP) and glass ply fibre reinforced polymer (GFRP) are reported on in conjunction with studies of concrete beams with high strength (HSC) under the category of with and without HyFRP laminates. The aim of this experimental work is to examine how alternative sequences of CFRP and GFRP ply of hybrid FRPs effect the enhancement of the high strength concrete beams. For the purpose of this study, there are a total of seventeen HSC beams cast. One of the beams was cast without HyFRP to act as a guiding beam, and the residual sixteen beams were cast with HyFRP using reinforced concrete and various combinations of carbon ply fibre reinforced polymer (CFRP) and glass ply fibre reinforced polymer (GFRP). The sequences in which hybrid FRP layers are attached serve as the primary variables in this test. Concrete with reinforcements after laminating beams with two, three, and even four layers of HyFRP, a load was applied in the form of static to the beams until they failed. The findings of the tests lead one to the conclusion that the repercussions of hybrid FRPs on the ductility of HSC beams are strengthened differently depending the order of the FRP layers.

Enhanced vibration damping and viscoelastic properties of flax/epoxy composites and their carbon fibre hybrid laminates

The damping and viscoelastic properties of flax/epoxy composites and their carbon fibre hybrid laminates are investigated. For this purpose, four different types of composite laminates using varied stacking sequences were fabricated by vacuum infusion process. The influence of various parameters on the vibration damping behaviour of flax and flax/carbon hybrid systems is investigated by using two techniques:shaker system utilising half-power bandwidth and dynamic mechanical analysis. In order to show the correlations between damping and mechanical properties, three-point bending tests are used to determine the bending stiffness of each stacking sequence. The results indicate that the location and number of flax plies contribute to the damping behaviour while the bending stiffness is mainly governed by location of carbon plies. Results show that the damping ratio varies for each vibration mode. Specimen type D, which contains the fewest number of carbon plies, exhibits higher values for both flexural stiffness and damping ratio compared to configuration B, which has the highest number of carbon layers. When comparing configurations B and C, it is observed that by trading off 8.1% of flexural stiffness, a substantial 34% increase in damping ratio was achieved in the second vibration mode.

Multivariable Signal Processing for Characterization of Failure Modes in Thin-Ply Hybrid Laminates Using Acoustic Emission Sensors.

The aim of this study was to find the correlation between failure modes and acoustic emission (AE) events in a comprehensive range of thin-ply pseudo-ductile hybrid composite laminates when loaded under uniaxial tension. The investigated hybrid laminates were Unidirectional (UD), Quasi-Isotropic (QI) and open-hole QI configurations composed of S-glass and several thin carbon prepregs. The laminates exhibited stress-strain responses that follow the elastic-yielding-hardening pattern commonly observed in ductile metals. The laminates experienced different sizes of gradual failure modes of carbon ply fragmentation and dispersed delamination. To analyze the correlation between these failure modes and AE signals, a multivariable clustering method was employed using Gaussian mixture model. The clustering results and visual observations were used to determine two AE clusters, corresponding to fragmentation and delamination modes, with high amplitude, energy, and duration signals linked to fragmentation. In contrast to the common belief, there was no correlation between the high frequency signals and the carbon fibre fragmentation. The multivariable AE analysis was able to identify fibre fracture and delamination and their sequence. However, the quantitative assessment of these failure modes was influenced by the nature of failure that depends on various factors, such as stacking sequence, material properties, energy release rate, and geometry.

Thin Hybrid Hemp/Carbon Fiber Composites: Manufacturing, Flexural, and Impact Behavior

This work is focused on the manufacturing and mechanical characterization of hybrid thin laminates in which the reinforcement is a combination of woven carbon and hemp fibers. Two types of hemp fabrics that differ in areal density were adopted for the production of the hybrid samples in sandwich configuration (1.8 mm in thickness), and pure carbon laminates were fabricated as reference. An ad-hoc manufacturing process was presented, and low-velocity impacts (at 2 and 5 J) and flexural tests were carried out. The results proved that, depending on the required performance, two carbon plies can be replaced by one hemp ply without affecting the performance of the structure while at the same time enhancing its sustainability.

Multivariable numerical optimisation and parametric study for a new kick-stage space vehicle for LEO applications

This research article presents a numerical optimisation and parametric study regarding the design process of a new innovative kick-stage component for aerospace applications. Given the intense rush for space-related services and its expected growth over the next few years, more dedicated rockets capable of delivering small satellites into their desired orbits are becoming increasingly popular. Modern design practices of globally elastic and locally plastic structures are commonly used in solutions nowadays. Aligned with more complex shapes of mechanical components, they play a crucial role in optimising mass and volume. During the last few years, aerospace structures have evolved from metal structures to laminated composite and/or sandwich-based ones because of the advantages regarding strength, stiffness-to-density ratios, flexibility, and durability, just to mention a few. This study presents a comprehensive analysis involving the conceptualisation, testing, optimisation, and design of a kick-stage structure using aluminium-based and composite-based models while illustrating how multivariable studies can be used after optimisation analysis to reach a manufacturable and efficient design. Several specimens were analysed to capture their frequency response and eigenmodes, indicating that without proper reinforcement, the structure does not have enough stiffness and structural performance to handle the frequency limits required and is not suitable to the space and vibration environment that will be subjected to. Based on the outputs obtained and by comparing different solutions, the composite-based model that comprises a honeycomb sandwich structure emphasises advantages regarding mass and frequency response. Nevertheless, the study also explores in depth the influence of other design variables on the performance of the space structure such as the thickness and density of the aluminium ribs, thickness of the plates, geometric configuration of the elements, number of carbon plies, and thickness of the core, among others. The conclusions from this study will ultimately be used to decide which option will be selected as the final approach for the design.

Post repair high velocity impact behaviour of carbon-glass hybrid composite: Experimental and numerical study

In this work post repair high velocity impact behaviour of carbon-glass hybrid composite was investigated. Two parent hybrid laminates(H1:G2C4G2 and H2:C2G4C2), two double sided patches (P1: G2C2 and P2: C2G2) and two single sided patches (P3: G2C4G2 and P4: C2G4C2)) were used in this study. The velocities in the range of 80-120 m/s were considered for this study. The effect of patch type and stacking sequence of patch plies on the impact resistance were studied. A 3D finite element model based on continuum damage mechanics approach was also developed to further understand the effect of the ratio of glass to carbon plies in a patch. The Hou damage initiation criteria and strain based damage evolution criteria were incorporated in the proposed numerical model. Overall, the P3 patch repair specimen performed better than all patch repaired specimens and the P2 patch repair specimen performed better than all double side patch repaired specimens. The P3 patch repaired specimen showed an 8% higher ballistic limit than the P2 repaired specimen patch. It was also observed that number of glass plies in the patch govern the damage development in the specimen and residual velocity of projectile.

Debonding-on-demand adhesive film using internal Joule heating effect of the steel-aramid braided reinforcement

Carbon fiber-reinforced polymer (CFRP) composite materials are widely employed as lightweight and high-strength materials. Recently, interest in reuse has increased in terms of price and environmentally friendly. In this study, a novel adhesive film that can selectively control adhesive strength was studied. This debonding-on-demand (DOD) adhesive film is stitched by stainless steel fibers to be heated up to 239.3 °C in 5 min through Joule heating. The polymeric adhesive layer in the midst of the carbon plies is thermally damaged, and then it is successfully delaminated with no further damage to the carbon fiber or CFRP matrix materials. Thermal, optical, and mechanical testing were performed on the prepared DOD film. It is noted that the optimal structure of DOD film includes electrical insulation layers, and the number of stitch lines is carefully designed for reliable bonding and debonding performance.

The Effect of Stacking Sequence on Fatigue Behaviour of Hybrid Pineapple Leaf Fibre/Carbon-Fibre-Reinforced Epoxy Composites.

This study examined the fatigue behaviour of pineapple leaf fibre/carbon hybrid laminate composites under various stacking sequences. The vacuum infusion technique was used to fabricate the symmetric quasi-isotropic oriented laminates, in which the stacking was varied. The laminate was tested under static and fatigue tensile load according to ASTM D3039-76 and ASTM D3479-96, respectively. Maximum tensile strength and modulus of 119.34 MPa and 6.86 GPa, respectively, were recorded for the laminate with external PALF ply and internal carbon ply oriented at [± 45°2, 0°/90°2]s (PCCP_45090). The fatigue tests showed that PCCP_45090 and CPPC_09045 (with internal PALF ply and external carbon ply oriented at [0°/90°2, ± 45°2]s) exhibited a higher useful life, especially at the high-stress level of the ultimate tensile strength. The normalised stress against the number of cycles showed that the stacking sequences of different ply orientations affected the fatigue behaviour more than the stacking sequences of the material. The laminate stacking sequence significantly affected the hysteresis energy and stiffness evolution. The scanning electron microscopy images showed that the fatigue failure modes included fibre pull-out, fibre breakage, matrix cracking, debonding, and delamination. The study concluded that PCCP_45090 exhibited an outstanding fatigue performance.

The wavenumber imaging of fiber waviness in hybrid glass–carbon fiber reinforced polymer composite plates

Out-of-plane waviness is one of the most common defects which degenerates the strength, stiffness, and fatigue life of hybrid glass–carbon fiber–reinforced polymer composites (FRPs). An accurate and high-speed non-destructive testing method is highly desired for large composite structures in industries. Ultrasonic phased array is a great candidate for such application. This paper applies the wavenumber algorithm to image the waviness in hybrid FRP plates which are a multi-layered medium. The central frequency of 5 MHZ is chosen in order to maximize the ply resonance. Transducers are migrated virtually to each interface between glass and carbon plies in order to overcome the difficulty of wave propagation analysis in such multi-layered system. The wavenumber algorithm demonstrates a better computational performance compared to that of the traditional total focusing method (TFM) in time domain up to 6 times. The glass ply depth and waviness angle can be more accurately presented with relative errors less than 1.5% and 14.8%, respectively. In addition, the resin-rich defect characterization is also achievable with a maximum error of 14.4%.

Quasi-Static Cyclic Response of Unidirectional Thin-Ply Hybrid Composites

Quasi-static cyclic loading of unidirectional (UD) thin-ply hybrid composites was conducted to assess the extent of stiffness loss with increasing applied strain. For this study, three types of hybrid configuration were examined: SG1/MR401/SG1, SG1/TR301/SG1, SG1/TR302/SG1, where SG is a high strength glass fibre and MR40 is an intermediate modulus carbon fibre while TR30 is a standard modulus carbon fibre. The strain at first carbon ply failure and the knee point strain (εk) for the SG1/TR301/SG1 hybrid is higher than for the SG1/TR302/SG1 hybrid. This is due to the ‘hybrid effect’ which provides a delay in damage initiation due to a constraint on broken carbon cluster development. For SG1/MR401/SG1 and SG1/TR302/SG1 configurations, the stiffness reduction over the course of loading was governed by fragmentation of the carbon plies and delamination between the carbon and glass plies. A smaller stiffness reduction for the SG1/TR301/SG1 configuration compared to the other hybrid configurations was observed with the fragmentation of the carbon ply as the main damage mechanism responsible for the reduction. With each loading cycle, there was a small amount of hysteresis and residual strain. The response of the UD thin-ply hybrid laminates are considered pseudo-ductile because the damage in the form of ply fragmentation and stable delamination, leads to gradual loss of stiffness. The stable delamination of this hybrid material is due to the low energy release rate of the thin carbon ply.

Enhanced interlaminar shear and impact performance of woven carbon/epoxy composites interleaved with needle punched high performance polyethylene fiber nonwoven

AbstractIn this study, high‐performance polyethylene (HPPE) fiber‐based needle punched nonwovens were interleaved in cross‐plied woven carbon fabric/epoxy composite laminates to enhance their interlaminar and impact properties. The placement of needle punched nonwoven interleaves exhibited considerable enhancement in interlaminar shear strength (ILSS), impact damage tolerance, and compression after impact (CAI) strength of laminates as evidenced by higher interlaminar strength, less absorbed energy, higher elastic energy, reduced damage degree, reduced out‐of‐plane deformation, higher load‐bearing capacity, and higher residual compressive strength as compared to control sample. In particular, the composite laminate with placement of interleaves in alternating sequence between carbon plies resulted in 205.76% increase in ILSS and 129, 103 and 85% increase in CAI at 10, 25, and 40 J impact energy, respectively. Moreover, damaged surface area and out‐of‐plane deformation reduced to 38.75% and 62.5%, respectively for the same specimen impacted at 40 J energy. These results suggest that the HPPE fiber‐based needle punched nonwoven interleaving can be adopted as a simple and low‐cost approach compared with other interleaving techniques, to enhance the resistance to delamination, impact performance, and damage tolerance of traditional structural laminates.

The Effect of Stacking Sequence and Ply Orientation on the Mechanical Properties of Pineapple Leaf Fibre (PALF)/Carbon Hybrid Laminate Composites.

In this paper, the effects of stacking sequence and ply orientation on the mechanical properties of pineapple leaf fibre (PALF)/carbon hybrid laminate composites were investigated. The hybrid laminates were fabricated using a vacuum infusion technique in which the stacking sequences and ply orientations were varied, which were divided into the categories of cross-ply symmetric, angle-ply symmetric, and symmetric quasi-isotropic. The results of tensile and flexural tests showed that the laminate with interior carbon plies and ply orientation [0°, 90°] exhibited the highest tensile strength (187.67 MPa) and modulus (5.23 GPa). However, the highest flexural strength (289.46 MPa) and modulus (4.82 GPa) were recorded for the laminate with exterior carbon plies and the same ply orientation. The fracture behaviour of the laminates was determined by using scanning electron microscopy, and the results showed that failure usually initiated at the weakest PALF layer. The failure modes included fibre pull-out, fibre breaking, matrix crack, debonding, and delamination.

Low-velocity impact resistance of thin-ply in comparison with conventional aluminium-carbon laminates

This study present investigation on the low-velocity impact resistance of fibre metal laminates consisting of aluminium layers and a thin-ply carbon fibre reinforced polymer. A thin-ply effect is compared with fibre metal laminates consisting of conventional thickness plies. Low-velocity impact tests are conducted with impact energies ranging from 2.5 J to 30 J. The low-velocity impact behaviour of conventional and thin-ply laminates is estimated and compared by analysis of key characteristics describing impact during the impactor-laminate contact. In addition, impact damage of the laminates is analysed, focusing on the identification of dominant damage modes and locations. Results demonstrate that the use of a thin-ply carbon fibre reinforced polymer neither increases the low-velocity impact resistance of the laminates nor significantly changes their low-impact impact response as compared to the laminates with conventional ply thickness. Results demonstrate that the damage mechanism of the composite thin plies does not significantly differ from that of the conventional carbon plies. Results also confirm that the use of thin-ply fibre metal laminates is an interesting and promising materials solution.

Environmental durability of carbon/flax fiber hybrid composites

Hybridization of synthetic fibers with natural fibers is receiving more attention in recent years. Experimental study on the durability of carbon/flax fiber reinforced polypropylene composites and single flax fibers was carried out. Three composite lay-ups were designed by altering the position of the carbon fiber ply, i.e., pure flax/polypropylene laminates, laminates with flax ply at the surface and laminates with the carbon ply at the surface. Samples were exposed to water immersion ageing at elevated temperature until saturation. The transport law of moisture in hybrid composites and mechanisms of possible change in microstructures and mechanical properties were particularly explored. Carbon fibers reduced the amount of water absorption in flax/polypropylene composites and improved their mechanical properties. These beneficial effects were optimum when carbon fibers were placed at the outer layers. However, the interface between the carbon ply and flax ply was vulnerable to both hygrothermal attack and delamination. After hygrothermal ageing, the tensile and flexural properties of the laminates decreased while the tensile failure strain increased, primarily due to plasticization and fiber/matrix interface deterioration. Single flax fibers which were exposed to the same ageing condition also experienced decrease in strength and modulus. However, elongation-at-break of single flax fiber decreased after ageing.

Structuring the thermoplastic interleaf with lotus-leaf-like structure and its interlaminar toughening for CFRPs

A new kind of self-supporting thermoplastic film with two-sided lotus-leaf-like structure was prepared and its effect on the interlaminar fracture toughness of carbon fiber/epoxy composite was studied. Phenolphthalein modified polyetherketone films with uniform, large scaled lotus-leaf-like structure were prepared by soft lithography. After interleaved with the structured films, the mode I interlaminar fracture toughness of the composite is slightly increased by 17%, whereas the mode II interlaminar fracture toughness is substantially increased as high as 325%. It is found that a special interlayer structure was formed, which contains thermoplastic nails and thermoplastic-rich layer. The mode I fracture path occurred mainly inside the carbon plies, whereas the mode II fracture path propagated through the highly tough thermoplastic nails and the thermoplastic-rich layer, and it frequently deflected near the thermoplastic nails, causing a high energy dissipation. This new method for preparing structured interleaves is expected to provide a new route for interlayer design.

Fatigue behaviour of pseudo-ductile unidirectional thin-ply carbon/epoxy-glass/epoxy hybrid composites

This paper is the first detailed investigation of the fatigue behavior of pseudo-ductile unidirectional (UD) thin-ply interlayer hybrids made of thin-ply carbon/epoxy plies sandwiched between standard thickness glass/epoxy plies under two scenarios: without any initial damage (pristine hybrids) and after the introduction of damage in the laminates by loading past the pseudo-yield point (overloaded hybrids). The laminates were subjected to different percentages of the critical stress level at which multiple fragmentation of the carbon plies was established (knee-point stress). The stress levels for fatigue delamination initiation and growth were evaluated experimentally. Based on the experimental work, it was observed that (1) when pristine hybrid composites were fatigued well below the carbon failure strain, at a stress level of 80% of the knee-point stress, there is no stiffness reduction after a significant number of cycles (105 cycles) (2) gradual stiffness reduction and very slow delamination growth was observed for pristine hybrid composites when fatigued at 90% of the knee-point stress, (3) when overloaded hybrid composites were fatigued at 90%, 80% and 70% of the knee-point stress, they did not fail immediately but delaminated slowly (4) the slow growth was due to the low energy release rate of the thin-ply hybrid composites (5) the strain energy release rate approach related to delamination rates provides a good way to characterize the fatigue damage accumulation of overloaded hybrid composites and as a basis to predict the fatigue life.

Effect of interlayer carbon fiber dispersion on the low-velocity impact performance of woven flax-carbon hybrid composites

This work investigates the effects of interlayer hybrid fiber dispersion on the impact response of carbon-flax epoxy hybrid laminates at low carbon volume fractions, and benchmarks the mechanical performance enhancement against the non-hybrid flax epoxy. Five hybrid laminate stacking sequences with similar carbon-to-flax weight ratio were fabricated and subjected to low-velocity impact at three different energy values, generating non-perforated and perforated damage states. A virtual drop-weight impact test that models intralaminar failure based on continuum damage mechanics approach, and delamination using cohesive elements, was also implemented to evaluate the material behavior and damage development in the composites. Simulation results were then verified against experimental data. Results suggested that positioning stiffer carbon plies at the impact face does not necessarily lead to enhancement of the hybrid's impact properties. On the contrary, flax plies at the impacted side lead to significant improvement in impact resistance compared to the non-hybrid flax composite with similar thickness. Results of finite element analysis showed that carbon plies play a significant role in the hybrid laminate's energy absorption characteristics due to lower failure strain.

Effect of Paper or Silver Nanowires-Loaded Paper Interleaves on the Electrical Conductivity and Interlaminar Fracture Toughness of Composites

The effect of plant-fiber paper or silver nanowires-loaded paper interleaves on the electrical conductivity and interlaminar fracture toughness of composites was studied. Highly conductive paper was prepared by surface-loaded silver nanowires. The percolation threshold appeared at about 0.4 g/m2. The surface resistivity reached 2.3 Ω/sq when the areal density of silver nanowires was 0.95 g/m2. After interleaving the conductive papers in the composite interlayers, in-plane electrical conductivity perpendicular to the fiber direction was increased by 171 times and conductivity through thickness direction was increased by 2.81 times. However, Mode I and Mode II interlaminar fracture toughness decreased by 67.3% and 66.9%, respectively. Microscopic analysis showed that the improvement of conductivity was attributable to the formation of an electrical conducting network of silver nanowires which played a role in electrical connection of carbon fiber plies and the interleaving layers. However, the density of the highly packed flat plant fibers impeded the infiltration of resin. The parallel distribution of flat fibers to the carbon plies, and poor resin-fiber interface made the interlaminar fracture occur mainly at the interface of plant fibers and resin inside the interleaves, resulting in a decline of the interlaminar fracture toughness. The surface-loading of silver nanowires further impeded the infiltration of resin in the densely packed plant fibers, resulting in further decline of the fracture toughness.

Influence of ply blocking on tensile stiffness in woven flax–carbon hybrids

The influence of carbon ply blocking on tensile stiffness in interlaminar flax–carbon epoxy hybrids is studied through various lamination schemes of similar nominal fiber volume fractions. Finite element mesoscale analysis accounting for distortions induced during compaction in the thinner carbon plies as a result of crimp mismatch was conducted. These distortions are shown to undermine hybrid stiffness, the extent of which is less pronounced when plies are blocked due to fewer hybrid interfaces, denoting that higher stiffness is achievable with blocked carbon plies. Backed by experimental evidences, it is suggested that detailed analysis on hybrid stiffness should treat hybrid interface as an independent variable a priori, and that modeling tools for carbon–flax fiber reinforced composites should consider not only the nonlinearity of flax response but also the waviness of both fabrics.

Viscoelastic Behavior of Cellulose Coated Glass/Kevlar Epoxy Composite Laminates using Dynamic Mechanical Analyzer

The dynamic behaviour of fiber reinforced composites plays a significant role on the performance of the laminated composite materials. In the present study the dynamic characteristics of cellulose Glass Epoxy Composites (CGEC) and Cellulose Kevlar epoxy composites (CKEC) were investigated and compared with pristine glass epoxy (GE) and Kevlar Epoxy (KE) composites using Dynamic Mechanical Analyzer (DMA). Cellulose particles were liquefied in organic solvents such as Acetone, Dimethylformamide (DMF), Ethanol and Sodium Hydroxide (NaOH) to inspect the settling time and it was found that cellulose particles settled in short interval of time in solvents and hence NaOH was used to make solution as better dispersion with high settling time was observed with NaOH. The Glass and Carbon plies were coated with Cellulose using semi automated coating technique. The DMA test was conducted in accordance with ASTM 1867-13. The tests results revealed that initially all the samples exhibited high storage modulus but there was a small drop in storage modulus in the temperature range of 50-70˚C and considerable drop in storage modulus was observed in the temperature range of 70-90˚C and also it was found that composite laminates changed in state from solid to elastic beyond glass transition temperature (Tg)