Properties Of Composite Laminates Research Articles

Research on the flexural property of composite laminates with embedded PZT

Research on the flexural property of composite laminates with embedded PZT

Inspired by nacre: α-ZrP three-dimensional network structures for interlaminar toughening of laminates

This work study enhancing the mechanical properties of composite laminates by using a three-dimensional network structure that mimics the nacre-like structure. The optimal interlaminar structure was developed by utilizing α-ZrP with ultrasonic-assisted exfoliation for 6 minutes. The mode-I critical energy release rate (GIC) and mode-II critical energy release rate (GIIC) of the toughened composite are 104.44% and 74.20% higher than those of the unmodified sample. Observation of the region around the crack by SEM and OM reveals that the three-dimensional network structure across the fiber fabric undergoes energy dissipation behaviors, such as fracture, slip and pull-out when cracks penetrate thin walls. In addition, the effect of the thin-walled structure of the α-ZrP aerogel on interlaminar crack propagation is discussed, taking into account the inhomogeneous and multi-surface of the composite interfaces, and the toughening mechanism is investigated.

Flexural and impact performance of Kevlar/basalt fabric interlayer hybrid curved composites

FRP composite has become one of the most preferred materials in lightweight applications. Design freedom is a key benefit which is reflected in the choice of fibres, stacking sequence and others. Hybridisation of hard inorganic fibre and organic ductile fibres can lead to synergetic effects. In this paper, an interlayer hybrid curved laminated composite reinforced with woven Kevlar and basalt fabrics and manufactured by a hand lay-up process with epoxy resin was prepared. Experimental investigation on the flexural and impact properties of composite laminates has been performed. The results of the investigation showed that the placement of Kevlar fibres on the impact side can increase the impact and flexural strengths, sample H3 (K3B2K3B2) has the highest impact strength and absorbed energy among seven hybrid laminates, valued at 92.89 KJ/m2 and 2.48 KJ. Compared with H5(B4K6) improved 41.6% and 40.9%, respectively. However, H5 has the highest flexural strength, reaching 231.7 MPa. In addition, the use of basalt fabric on the impact reverse side or multi-layer hybrid structuring further improves the impact properties of the materials. A sandwich-structure composite with basalt layers in the middle and Kevlar layers on both sides shows further improvement in the flexural properties.

Synergistic mechanism of strengthening and toughening of tissue regulation response to Mg/Al composite laminates by hard plate accumulative roll bonding

The significance of light alloy in realizing the national strategy of energy saving and emission reduction and promoting the upgrading of the manufacturing industry is self-evident. Mg/Al composite laminates combine the lightweight of magnesium alloy and the plasticity and corrosion resistance of aluminum alloy. Traditional accumulative roll bonding technology relies on the advantage of introducing large deformation. Although high strength is obtained, it is often accompanied by a large loss of ductility, and there is a problem that it is difficult to balance strength and ductility. To solve this problem and optimize the process conditions, a new hard-plate accumulative roll bonding process is proposed in this paper, which is used to prepare high-performance Mg/Al composite plates, and the influence of forming temperature on the microstructure and mechanical properties of Mg matrix is studied. The results show that when the forming temperature is 350 °C, the properties of composite laminates are the best, the tensile strength can reach 243 MPa, the elongation is 14.7 %, and there are a lot of tearing edges and dimples on the fracture surface. At the same time, complete recrystallization can be realized at this temperature, and the opening of non-base slip can coordinate deformation stress, promote the dislocation slip, and reduce the dislocation density, SEM images show that there are no defects such as delamination at the interface, and a firm metallurgical bonding is achieved. It provides a new approach to the forming and manufacturing of high-quality lightweight heterogeneous composite laminates.

Mechanical properties of vinyl ester hybrid composite laminates reinforced with screw pine and glass fiber

<abstract> <p>The screw pine and E-glass fibers were hybridized in the vinyl ester resin matrix to prepare the hybrid composite laminates in the present communication. Hybrid composite laminates at the constant volume fraction of 35.12% has been fabricated using the hot press compression molding in two forms, namely dispersed and skin-core, to evaluate the mechanical properties. Mechanical properties of composite laminates were studied based on the various volume fraction of glass fiber content (0, 3.32, 8.15, 12.44 and 16.53 vol.%). The scanning electron microscopy (HITACHI S-3000N) was used to study the fracture surface of composite laminates. The results of hybrid composite laminates were compared with a neat resin sample and screw pine fiber (35.12 vol.%) alone composite. The results revealed that the mechanical properties of both the type of composite laminates increased as glass fiber addition was increased. The SPF18.59/GF16.53 hybrid composite laminate exhibits the highest level of mechanical properties because of the concentration and higher elongation percentage of glass fibers. Moreover, the skin-core type composites perform better than those of the dispersed type hybrid composites. Because of the stretching nature of screw pine fibers, they elongate when the load is transferred from glass fibers to screw pine fibers, resulting in an increase in mechanical properties. The property values were predicted using a theoretical model, and it was found that the two were in good agreement.</p> </abstract>

Low‐velocity impact response and post‐impact assessment of self‐healing composites with different stacking configurations of core–shell nanofibers

AbstractThis work investigates the low‐velocity impact (LVI) and self‐healing behavior of carbon fiber composite laminates interlaced with electrospun polyacrylonitrile core–shell nanofibers (PAN@CFRP). The main goal is to investigate the influence of different stacking configurations of core–shell nanofibers on the impact resistance and self‐healing properties of composite laminates. To achieve the purpose, three different stacking configurations were designed and tested alongside virgin specimens. The damage mechanism and self‐healing of laminates following LVI were determined using ultrasonic C‐scan and cross‐sectional microscopy examinations. At an impact energy of 14.1 J, the flexural strength of the post‐healing PAN‐3@CFRP specimen reached 95.0% of the initial value, whereas at an impact energy of 21.8 J, severe impact damage was observed in the laminates with different configurations. Among the laminates, the PAN‐1@CFRP specimen had the highest flexural strength after healing, which reached 80.1% of its pre‐impact strength. As observed, the impact resistance and self‐healing capacity of composites could be significantly enhanced by optimizing the distribution configuration of core–shell nanofibers for various impact energies.Highlights The introduction of electrospun core–shell nanofibers has not significantly compromised the mechanical properties of the composites, but rather enhanced their toughness. The addition of core–shell nanofibers significantly enhances the impact resistance of the composites and imparts excellent self‐healing properties to the material. The flexural strength of impact‐damaged specimens with different stacking configurations can be restored up to 95% of the undamaged specimen after repair treatment. Significantly improved impact resistance and self‐healing ability of laminates by optimizing the distribution configuration of core–shell nanofibers between composite layers.

Gamma-ray irradiation to achieve high tensile performance of unidirectional CNT yarn laminates

Continuous carbon nanotube (CNT) yarn fabricated from a floating catalyst chemical vapor deposition (FCCVD) method is treated under gamma-ray irradiation to enhance the mechanical properties of the CNT yarn and its unidirectional composite laminates. Gammy-ray doses varying from 50 kGy to 1200 kGy are used to irradiate CNT yarns and their microstructures, tensile properties and surface characterizations are studied. The graphitic structure change is not clear from the transmission electron microscopy, however, the specific tensile strength and modulus of yarn vary slightly within 10 % as the dose increased. This modulus trend coincides with mesoscopic distinct element modeling (mDEM) simulation results. Surface characterization shows additional oxygen functional groups and smaller contact angles after irradiation. Interestingly, the specific tensile properties of composite laminates also increase relative to the yarns, and the unidirectional laminate from CNT yarn treated with the optimal dose of 700 kGy achieves specific strength and modulus as high as 1.89 GPa/gcm−3 and 258 GPa/gcm−3, respectively, which are 30.9 % and 37 % increases compared to the control laminate. The results indicate that radiation-induced crosslinking among the CNTs and the formation of surface-active sites leads to enhanced load transfer in the yarns and promote CNT/resin interfacial bonding.

Effect of Fabric Areal Weight on the Mechanical Properties of Composite Laminates in Carbon-Fiber-Reinforced Polymers

The present work aims at studying the effect of the reinforcing fabric areal weight on the mechanical properties of composite laminates in carbon-fiber-reinforced polymers. Three different pre-impregnated 2 × 2 twill weaves, characterized by the different areal weight values of 380, 630, and 800 g/m2 were used to produce laminates. These areal weights were selected to represent typical values used in structural application. A hand lay-up technique followed by an autoclave cycle curing was employed to produce the laminates. The desired final thickness of the laminates was obtained by laying-up a different ply number, as a function of the areal weight and thickness of each fabric. Uniaxial tensile and in-plane shear response tests were performed on samples obtained from laminates after curing. Furthermore, the presence of voids in composite materials were detected by performing resin digestion tests. Finally, light optical microscopy and stereomicroscopy analyses allowed observing the different arrangement of the plies in the cross-sections of laminates after curing and evaluating the degree of compaction as a function of the reinforcing fabric used. It was demonstrated that the fabric areal weight significantly affects the mechanical performances of the composite laminates; specifically, the decrease in the areal weight of the twill weave leads to an increase in tensile strength, elastic modulus, and in-plane shear stress, i.e., of about 56.9%, 26.6%, and 55.4%, respectively, if 380 g/m2 and 800 g/m2 fabrics are compared. These results are crucial for an optimal material selection during the design process for industrial applications and help to better understand composite material behavior.

Improvement of the tensile properties of laminated composites reinforced with Heli‐Coil forms of carbon nanotubes

AbstractThe traditional composite laminated structures suffer from the absence of reinforcements in the thickness direction between the laminae and microfibers, which will result in poor interaction between the laminae, individual microfiber filaments, and the resin. In addition, out‐of‐the‐plane properties are generally dominated and controlled by poor matrix properties (e.g., mechanical, electrical, and thermal). Most prior investigations were focused on the use of straight carbon nanotubes (CNTs), graphene, or nanomaterials in particle forms to improve the resin properties. Our previous research has shown that CNTs with helical (Heli‐Coil) geometries (HCNTs) are more effective as a nanoscale reinforcement to improve the properties of polymeric resins. Because of their inertness, the interfacial bonding between CNTs and the resin is generally weak, and they can be easily pulled out of the resin (inefficient load transfer) if the CNTs are in their straight forms. However, the helical geometries of HCNTs can provide unique mechanical‐interlocking mechanisms between the constituents that can substantially improve their effectiveness as a nanoscale reinforcement, leading to improvements in composite performance, properties, and multifunctionality. In this research, HCNTs at low concentrations below 0.1 wt% were processed and then used to fabricate nanocomposite laminates. Tensile test specimens were carefully prepared following the ASTM D3039/D3039M standard and then tested, analyzed, and evaluated. Additionally, the fractured test specimens were inspected and analyzed using optical and 3D scanning laser‐confocal‐microscopy imaging. The test results showed improvements of 12.3%, 11.3%, and 17.5% for the tensile strength, modulus, and strain‐to‐failure, respectively. In conclusion, traditional fiber‐reinforced composites can considerably benefit from the helical forms of HCNTs.Highlights The helical geometry of CNTs (HCNTs) is more effective for composite reinforcement. HCNTs provide unique interlocking mechanisms between the composite constituents. HCNTs can considerably improve the multifunctional characteristics of the composites. HCNTs can considerably improve the tensile properties of composite laminates. Traditional composites can substantially benefit from the helical forms of HCNTs.

Composite Laminates for Aerospace and Packaging Fields

Composite materials have become increasingly popular and widely used in the present world due to their unique combination of properties that cannot be achieved by any single material. In the current study the mechanical properties of composite laminates (Jute, palm and banana fibers) were fabricated by varying groundnut husk and seashell powders quantities (5, 10, 15 and 20gms) in epoxy resin using hand layup technique. In according to the ASTM standards, a mixture of Epoxy (LY556) and Hardener (araldite) HY951 is used. The ratio of epoxy to hardener is 10:1. The material will be properly mixed for some time before being used to create laminates. Samples were fabricated with different compositions of jute, palm and banana fibers. Tensile, Compression properties of laminates were analyzed by testing composite laminates on universal testing machine. In this context the weight ratio of groundnut husk to seashell powder is 2:1. Analysis states that both the powders have impact on the mechanical properties of laminates. The impact of groundnut husk powder is slightly more on the laminates mechanical properties (tensile, compression) when related to seashell powder.

Experimental Study of Fiber Orientation on the Mechanical Properties of Glass Fiber Reinforced Thermoplastic Composites

This research work aims to perform a comparative study on the effect of fiber orientation distribution (FOD) on the mechanical properties of composite laminates for aircraft and automobile structure. The objective of this project works is to use an analysis method to study the effect of significant parameters namely, with and without orientation on the glass fibre epoxy composites. The experimental work is used to investigate the mechanical behavior and to examine the properties with respect to fibre orientation on the composite laminates. The glass fibre orientation characteristics for the composite laminates is considered since they affect the strength of the specimen laminates. In this connection, the specimens were fabricated with different orientations and undergone for mechanical testing like tensile, compression and impact tests with Data Acquisition System. The experimental results indicate that the specimens with orientation provide more strength, high stiffness and good toughness than the normal specimens without orientation.

Supersonic flutter of variable stiffness circular cylindrical shells

Curvilinear reinforcement fibres allow to tailor the elastic properties of composite laminates in space, leading to Variable Stiffness Composite Laminates (VSCL). In this work, the aeroelastic stability of VSCL cylindrical shells under a supersonic airflow along the axial direction is analysed in order to verify if curvilinear fibres can be used to increase the flutter speed. A linear mathematical model for thin circular cylindrical VSCL shells is developed for that purpose. The aerodynamic pressure caused by the supersonic airflow is modelled recurring to the linearised piston theory. The p-version of the finite element method is used to transform the differential equations of motion from partial to ordinary. Using the latter, eigenvalue problems are defined to obtain the natural frequencies and mode shapes of vibration, and the critical flutter conditions. Various types of curvilinear fibre paths are explored, to find paths that result in higher values of critical flutter free stream pressure. The values are compared with the ones of conventional, constant stiffness, composite laminated shells.

A Review of Electrospun Nanofiber Interleaves for Interlaminar Toughening of Composite Laminates

Recently, polymeric nanofiber veils have gained lot of interest for various industrial and research applications. Embedding polymeric veils has proven to be one of the most effective ways to prevent delamination caused by the poor out-of-plane properties of composite laminates. The polymeric veils are introduced between plies of a composite laminate, and their targeted effects on delamination initiation and propagation have been widely studied. This paper presents an overview of the application of nanofiber polymeric veils as toughening interleaves in fiber-reinforced composite laminates. It presents a systematic comparative analysis and summary of attainable fracture toughness improvements based on electrospun veil materials. Both Mode I and Mode II tests are covered. Various popular veil materials and their modifications are considered. The toughening mechanisms introduced by polymeric veils are identified, listed, and analyzed. The numerical modeling of failure in Mode I and Mode II delamination is also discussed. This analytical review can be used as guidance for veil material selection, for estimation of the achievable toughening effect, for understanding the toughening mechanism introduced by veils, and for the numerical modeling of delamination.

Synergetic improvement of the thermal conductivity and interlaminar fracture toughness of carbon fiber/epoxy composites by interleaving BN@ZnO particles

AbstractSynergetic improvement of the thermal conductivity and interlaminar fracture toughness of carbon fiber/epoxy resin composites (CF/EP) is a challenging research job. In this work, hexagonal boron nitride coated ZnO (BN@ZnO) particles were firstly prepared by sol–gel method and BN@ZnO composite laminates were manufactured by mold pressing process. X‐ray diffraction, x‐ray electron spectroscopy and scanning electron microscopy were used to analyze the structure, chemical components and morphology of the BN@ZnO and composite laminates. The effects of BN@ZnO on the impact strength, model II interlaminar fracture toughness (GIIC) and thermal conductivity of composite laminates are investigated. The results show that the interlaminar fracture toughness and thermal conductivity of composite laminates are synergistically enhanced owing to the introduction of hybrid fillers with different dimensions and morphology. The thermal conductivity of the 10 wt% BN@ZnO coated composite laminates is increased by 78% and 90% at 25 and 100°C, respectively. The mechanical properties of composite laminates are enhanced. The model II interlaminar fracture toughness of 2 wt% BN@ZnO composite laminates is 15.4% higher than pure laminate. This work is of significance to realize the structural and functional integration of composite materials.

Finite Element Analysis of Flexural Behavior of Shape Memory Alloy Hybrid Composites Laminates

In this paper, experiments and finite element analysis methods were adopted to study the flexural performance of shape memory alloy hybrid composites (SMAHC). The effect of embedding content and position of shape memory alloy (SMA) wire on the flexural properties of composite laminates was analyzed, and the optimal content and position of SMA wire were obtained. The optimal number of SMA wires for SMAHC laminates (B-2) is four. Compared with GFRP laminates, the flexural modulus of B-2-4 laminates increases by 5.19%, while the strength decreases by 5.76% on average. The finite element model of the SMAHC laminate was established by using ABAQUS finite element analysis software, and the validity of the model was verified by the comparison between the simulation results and the experimental results. The microscopic morphology results show that the weak interface between the matrix and SMA has a certain influence on the flexural performance of SMAHC specimens.

Mechanical properties of Assam’s bamboo-epoxy composite laminates – An experimental investigation

The dominance of contemporary composite materials has reached heights as well worth weight-saving materials. The current policies for manufacturing cost-effective and sustainable composites lead toward utilizing natural materials in polymeric matrixes. Bamboo is one of the rapidly growing crops which is as stronger as timber and can be utilized in developing semi-replaceable industrial products. Lack of adequate standardization and codes restricts its direct utilization for commercial use. The current study aims to investigate the mechanical properties of composite laminates from high-performance bamboo strips collected from the North-Eastern (NE) region of India. In this study, the alkali-treated bamboo samples were infiltrated with epoxy resin using VARTM (vacuum-assisted resin transfer molding) process. The Fourier transform infrared spectroscopic (FTIR) and Field Emission Scanning Electron Microscopy (FESEM) analysis is carried out to have a better understanding of the chemical composition, and surface morphology. It has been confirmed from the obtained results of FTIR that lignin content is greatly reduced from the delignified samples. In addition, the FESEM images have depicted an outsize layer of epoxy along the fiber cross-section and some pores have been observed as unfilled. On the other hand, these composites are also subjected to tensile, compressive, flexural, and impact tests. The composites achieved a maximum tensile strength and stiffness of 259 MPa and 16.8 MPa which is 253 % and 384 % higher than neat epoxy. However, the strength of the alkali-treated samples is found to be decreased which may be due to the loose fiber bundles and holes formed during the chemical treatment. Improvements in dimensional stability against moisture are achieved for the composites with treated fibers which can be related to better fiber-matrix interlocking. The investigation of the mechanical strength of these highly-cellulosic fiber composites is conducted through various experiments and the results are validated with theoretical equations. It is found that the theoretical values are in good agreement with the experimental data with an error < 15 %. These composites demonstrate large-scale production of lightweight, environmentally friendly, and sustainable future materials with high strength and stiffness. • Laminates with three species of bamboo from the North-Eastern region are developed. • A significant increment of 253 % in strength of composite laminates is observed. • Both longitudinal and transverse material properties are evaluated. • Experimental results differ by < 15 % error from theoretical. • Simultaneously, an increase in bending and toughness is observed.

Span length effect on flexural properties of composite laminate reinforced with a plain weave carbon fiber fabric in a polymer matrix

Abstract This article focuses on an experimental study of the flexural response of a polymer composite laminate (CL) reinforced with a plain weave carbon fiber fabric. The aim of this research is to investigate the effect of the span length-to-specimen thickness ratio on the flexural properties of the selected CL. The laminate specimens were tested in the three-point flexure configuration for span length-to-specimen thickness ratios of 16, 20, 32, 40 and 60. The investigations were carried out to identify on-axis and 45° off-axis flexural responses of the CL. For this reason, two types of rectangular flat specimens were prepared, differing in reinforcement orientation relative to the support span. Using the special code, the lay-up of the specimens was designated as [(0/90)F]8 and [±45 F]8, respectively. It was found that the flexural modulus and flexural strength of the specimens depend on the span length-to-specimen thickness ratio. Despite testing the same CL, the response of the specimens to the change in the span length is different. In addition, it was concluded that the span length also has a significant influence on the final failure of the laminate specimens.

Failure analysis and experimental study on bolted composite joints based on continuum damage mechanics

This study focuses on the numerical analysis and experimental evaluation of failures and damages in the bolted joints of CFRP composite laminates under tensile loads. Firstly, failure criteria for fiber and matrix are established based on the Puck/LaRC failure criteria and in-situ strength theory. A mechanical model for composite damage analysis is established by adopting the nonlinear stiffness degradation method. Secondly, the tensile properties of composite laminates and perforated plates are analyzed using a mechanical model developed above. Finally, we conducted an experimental investigation of the composite joints and finite element analysis of their failure and damage evolution. The comparison between the calculated and experimental results demonstrated that the employed mechanical model and calculation method could accurately predict the strength and damage of carbon fiber composite joints under tensile loads. Moreover, to evaluate the fracture angle in matrix failures, we proposed a new method, which is found to be beneficial in improving the accuracy and efficiency of evaluating fracture angles.

Study on behavior and mechanism of low-velocity impact and post-impact flexural properties of carbon-aramid/epoxy resin laminated composites

This paper aims to investigate the effects of the hybrid effect and stacking configuration of carbon fiber and aramid fiber fabric on the low-velocity impact and post-impact flexural properties of composite laminates. The damage characteristics and mechanism of the composite surface and interior were analyzed. The results show that the ACACA laminated structure combines the advantages of carbon fiber’s high strength and aramid fiber’ high toughness, showing the most excellent impact resistance and the residual flexural property. Micro-CT analysis indicates the damage modes of ACACA laminates under impact is internal delamination failure, and that the delamination phenomenon is evenly distributed along the thickness direction. The damage modes under post-impact flexural are fiber kink, drawing and delamination. This is because aramid fibers distributed at intervals in the laminate can effectively spread the stress to a larger area along the in-plane direction, thus reducing the material damage caused by stress concentration.

Mechanical properties prediction of composite laminate with FEA and machine learning coupled method

In order to predict mechanical properties of composite laminate, a method coupling finite element analysis (FEA) and machine learning is established to analyze three examples of composite laminates, such as failure factor of Puck theory under random stress state, failure factor and critical buckling eigenvalues of open-hole laminate. By writing Abaqus script, parametric FEA models of composite laminates are built and large samples are generated. Artificial neural network (ANN) model and random forest (RF) model are set up to learn these virtual samples to predict their corresponding mechanical properties for these examples. By analyzing predicted results and FEA values of these mechanical parameters, predicted data are well consistent with the curves of FEA values and the calculated root-mean-square errors are much smaller, which proves this FEA and machine learning coupled method is effective. Even if these errors predicted by ANN model are smaller than RF model, and the learning processes of RF model take less time, these methods with ANN model and RF model are all appropriate to predict mechanical properties of composite laminates.