Polymer Composite Structures Research Articles

Natural Frequencies of Soft-Core Composite Sandwich Plates Reinforced by FG Graphene Platelets

Superior mechanical properties such as ultrahigh stiffness and strength along with amazing physical properties have led to the use of nano graphene platelets (GPLs) as a reinforcement in polymer composite structures such as sandwich plates. In this research, free vibration analysis of rectangular sandwich plates with functionally graded (FG) GPL-reinforced face sheets and a soft core is investigated. A high-order three-layer accurate sandwich plate theory is employed to model the soft-core sandwich structure. Third order shear deformable plate theory is applied for functionally graded graphene nano-composite face sheets while second and third order polynomials are used for displacements of the soft core. In this theory, the transverse flexibility of the core as well as the continuity conditions of transverse shear stresses are assumed. Hamilton’s principle is applied to extract the motion equations and the corresponding analytical solutions are presented. The effects of materials properties and geometrical parameters on the natural frequencies of the sandwich plates are studied. A comparison of the present results in particular cases with those of published studies confirms the accuracy of the present analysis. Results show that the natural frequencies of the sandwich plates are enhanced by reinforcing the face sheets with GPLs.

Low-Profile Polymer Composite Radar Absorber Embedded With Frequency Selective Surface

This paper proposed a novel design for a thin, lightweight polymer composite Radar Absorber (RA) with broadband bandwidth in the frequency range 2.8-9.6 GHz. A 3-mm-thick, thin polymer composite structure comprised of glass fiber, epoxy resin, and FSS films was then fabricated using the hand layup process. The β-phase behaviour enhanced polyvinylidene fluoride (PVDF) through electrospinning was deposited on a frequency selective surface (FSS). The PVDF phase structure was evaluated using X-Ray diffraction (XRD). The formation of nanofibers was evaluated by scanning electron microscopy (SEM). A significant increase in the absorption of electromagnetic (EM) waves with a broad operational bandwidth is produced by the addition of FSS to the glass fiber. Experiments were carried out and assessed by comparing the results to numerical models in CST Microwave Studio, indicating that the RA integrated with PVDF coated FSS has an operational bandwidth of 2.8-9.6 GHz and a reflectivity of less than -10dB. Finally, the absorption and mechanical characteristics of the fabricated Radar Absorbing Structure (RAS) was also investigated.

Experiments and Simulations on the Shape Memory Process of Thermally-Induced Shape Memory Polymer Composite Thin-Wall Structure Considering Progressive Damage

Experiments and Simulations on the Shape Memory Process of Thermally-Induced Shape Memory Polymer Composite Thin-Wall Structure Considering Progressive Damage

Silica aerogel infused hierarchical glass fiber polymer composites

Hierarchical systems can address the matrix-dominated failures of structural fiber polymer composites. Here, a new synergistic hierarchical structure combines conventional structural glass fibers with a bi-continuous silica-based aerogel matrix; both pure-silica and organically-modified silicate aerogels are demonstrated. When infused with an epoxy matrix, this type of hierarchical architecture showed a marked improvement in mechanical properties: without any loss in modulus, both the compressive strength and the interlaminar shear strength increased by up to 27%, relative to the equivalent glass-fiber reinforced epoxy composite baseline. The bi-continuous network modification strategy uses industrially-relevant infusion techniques, at or near room temperature, and retains a similar final composite density (within 2%). The strategy presented here provides a versatile and readily applicable means to improve state-of-the art continuous fiber reinforced composite systems in compression and offers an opportunity to develop a new generation of composite materials.

Sustainable 4D printing of magneto-electroactive shape memory polymer composites

Typical techniques for creating synthetic morphing structures suffer from a compromise between quick shape change and geometric complexity. A novel approach is proposed for encoding numerous shapes and forms by magneto-electroactive shape memory polymer composite (SMPC) structures and integrating sustainability with 4D printing (4DP) technology. Electrically driven, remote controllability, and quick reaction are the features of these sustainable composite structures. Low-cost 4D-printed SMPC structures can be programmed remotely at high temperatures to achieve multi-stable shapes and can snap repeatedly between all programmed temporary and permanent configurations. This allows for multiple designs in a single structure without wasting material. The strategy is based on a knowledge of SMPC mechanics, magnetic response, and the manufacturing idea underlying fused deposition modelling (FDM). Iron-filled magnetic polylactic acid (MPLA) and carbon black-filled conductive PLA (CPLA) composite materials are investigated in terms of microstructure properties, composite interface, and mechanical properties. Characterisation studies are carried out to identify how to control the structure with a low magnetic field. The shape morphing of magneto-electroactive SMPC structures is studied. FDM is used to 4D print MPLA and CPLA adaptive structures with 1D/2D-to-2D/3D shapeshifting by the magnetic field. The benefits of switchable multi-stable structures are reducing material waste and effort/energy and increasing efficiency in sectors such as packaging.Graphical

The orientation and inhomogeneous distribution of carbon nanofibers and distinctive internal structure in polymer composites induced by 3D-printing enabling electromagnetic shielding regulation

Carbon nanofiber (CNF)/polycaprolactone (PCL) composites were three-dimention (3D) printed into electromagnetic interference (EMI) shielding parts. 3D-printing process led to an inhomogeneous CNFs distribution in printed composites. The special high-resistance “internal surfaces” introduced between printed threads reduced the conductivity of printed parts and resulted in characteristic secondary percolation phenomena. Meanwhile, the accelerated melt flow in nozzle oriented CNFs in composites along the printing direction, increasing the percolation threshold compared to the random arrangement. As two stage of percolation networks formed, the 3D-printed CNF/PCL parts exhibited excellent EMI shielding performance, with EMI shielding effectiveness value up to 58.7 dB. By controlling the packing density of the printed part, a large number of apertures and heterogeneous interfaces were easily introduced into the interior of parts. It promoted multiple reflection and absorption of electromagnetic waves inside the parts, and enabled adjustment of weight and shielding effectiveness. Therefore, the 3D printing enabled the flexible formation of complex porous structures. From basic materials to designed components, the 3D printing technology can facilitate the transformation of shielding materials into high performance components that are finely designed both internally and externally, making it a promising technology in the field of manufacturing lightweight, high performance EMI shielding materials.

Single-Impact Failure of Multi-Layered Automotive Coatings: A Finite Element-Based Study

Automotive coatings are a multi-layered polymer composite structure whose impact resistance is closely related to the appearance and safety of a vehicle. Since experimental methods are of high cost and poor repeatability, in our work, a finite element model is developed for the single-impact failure of automotive coatings. In this model, a multi-mechanism damage model and a large deformation cohesive zone model are employed to account for the polymer-ply and interlaminar failures of the coating, and some rate-dependent material models are adopted to capture the effect of impact velocity. The simulated results indicate that the proposed model can reproduce the failure patterns of automotive coatings well. In addition, the impact failure mechanisms of the coating are revealed. Numerical findings show that both brittle and ductile failures are found in the coating and there are three stages for the propagation of the delamination crack. Finally, we numerically investigate the effects of primer mechanical properties, i.e., Young’s modulus, yield strength, and re-hardening modulus, on the impact resistance of automotive coatings. Our work is helpful to the design of coating, which can improve the impact resistance of automotive coatings.

Effect of the number of stiffeners on the lateral deformation behavior of additively manufactured thin-walled cylindrical tubes

Nowadays, thin-walled cylindrical tubes with stiffeners have been rapidly considered in crashworthiness applications owing to their outstanding energy absorption characteristics and comparatively light weight. This research article deals with the influence of the internal linear stiffeners with varying numbers on the lateral crushing characteristics and impact energy absorbing response of cylindrical tubes subjected to quasi-static loading through experimental approaches. Five different configurations were proposed and all the tubes were additively manufactured through Fusion Deposition Modeling (FDM)-based 3 D printing method. Eventually, the fabricated tubes were tested under quasi‐static lateral crushing force and their crashworthiness characteristics were determined. The obtained results revealed that the PLA-CF-based C6S tube exhibited Specific Energy Absorption of 4.99 kJ/g and attained Crush Force Efficiency is 98.68%. Overall outcomes reported that both the carbon fiber reinforced polymer composite tube structures presented better crushing behavior and enhanced energy absorbing capability. Therefore, the proposed linear stiffener induced cylindrical tubes could be employed as a crash box for absorbing energy under lateral impact.

A Fatigue Model to Predict Interlaminar Damage of FRP Composite Laminates Subjected to Mode I Load.

In fiber-reinforced polymer (FRP) composite laminate structures operating under fluctuating stresses, interface delamination is seen as one of the significant damage mechanisms. The constant degradation of their relatively low interlaminar strength and stiffness are the primary reasons for delamination. This study develops an interlaminar fatigue damage model to quantify the mechanics of the damage process and address the reliability of composite structures. The model considers the failure process in two stages: (1) damage due to degradation of interlaminar elastic properties, and (2) damage due to dissipation of fracture energy through the damage evolution process. The model is examined for a case study of mode I fatigue loading of a carbon-fiber-reinforced polymer (CFRP) composite laminate. The results show that the interlaminar normal stress is confined to the crack front region, with tensile stress peaks at 70% of the interlaminar strength. Furthermore, a stable interface crack growth is predicted initially, followed by a sudden crack "jump" at 14,000 cycles. The simulation results are compared with the experimental data, with very good agreement, showing a successful validation of the fatigue model.

Regulation binary electromagnetic filler networks in segregated poly(vinylidenefluoride) composite for absorption‐dominated electromagnetic interference shielding

AbstractExcellent conductivity and optimized impedance matching are vital for superior absorption‐dominated electromagnetic interference (EMI) shielding. An efficient binary electromagnetic filler network regulation method has been proposed. Poly‐ (vinylidenefluoride)‐ferroferric oxide‐reduced graphene oxide/single‐wall carbon nanotube (PVDF‐Fe3O4‐RGC) composite has been synthesized as a layered segregated polymer composite structure by using an electrostatic assembly and hot compression strategy. Binary electromagnetic filler networks have surpassed the obstacles of magnetic materials in conductive networks, and are thereby beneficial for outstanding conductivity and impedance matching. Therefore, a superior conductivity of 1.28 S cm−1 and an outstanding electromagnetic shielding interference and effectiveness of 44.5 dB have been obtained for loading of 2.02 vol.% single‐wall carbon nanotubes (SWCNTs), with an absorption rate larger than 85.0% in the X‐band. The enhanced EMI shielding performance is attributed to the regulation of the binary electromagnetic filler network.

A review on epoxy granite reinforced polymer composites in machine tool structures – Static, dynamic and thermal characteristics

AbstractMachine tool structures produced with Epoxy Granite reinforced polymer composites (EGPCs) have gained prominence in recent years and have replaced conventional cast iron materials and other metals due to its remarkable damping characteristics. However, machine tool structures manufactured with EGPCs tends to exhibit limited strength, stiffness and stability. Such challenges in EGPCs are resolved by incorporation of steel as additional reinforcement and enhanced mechanical properties are observed in these hybrid machine‐tool structures. Hybrid epoxy granite machine tool structures with enhanced mechanical performance are prone to thermal errors resulting in machining inaccuracies and limited performance. Thermal errors induced in machine tool structures could be attributed due to effect of temperature distribution and displacements at the Tool Center Point (TCP). This review work carried out focuses predominantly on design methods adopted in resolving the challenges identified in development of machine tool structures and further analyses results of several polymer concrete‐based machine tool structures with regard to static, dynamic and thermal characteristics. Several review works conducted earlier have discussed the results of static and dynamic characteristics, whereas this review work provides additional information on thermal based errors induced and discusses the methods adopted in compensation of thermal errors. In this review paper, research studies pertaining to static and dynamic characteristics of different machine tool structures performed in last three decades have been discussed and a wholistic information is provided in relation with static, dynamic and thermal characteristics and properties toward developing a machine tool structure with a novel, newer class or alternative materials.

Estudio comparativo de las propiedades mecánicas de materiales compuestos de fibra de carbono para el desarrollo de elementos estructurales aeronáuticos.

  Carbon fibre reinforced polymer composite material structures continue to be, despite the tremendous technological maturity achieved in recent decades, one of the most promising options to address the challenges of the aeronautical industry with respect to behaviour in the face of efforts such as improvements, regarding weight or costs. Ongoing demands to address major societal challenges, promote industrial leadership in Europe, and address aviation decarbonisation for the purpose of protecting the environment drive the demand for more optimal materials designed to improve these aspects. The previous tasks carried out to complete the test campaign will be described, showing its plan and design, details of preparation, assembly of the specimens and the execution of the tests. The philosophy proposed by Airbus (ADS) is presented with the consolidation of admissible design against alterations of the material that could realize its evolution or arise in the manufacturer's batches. Observing changes in the material, leading to the improvement of its mechanical and handling characteristics, a comparison has been made by Airbus with the one used previously for the determination of admissible design. It is intended to incorporate assessments of effects associated with the process of its industrialization. Once the results and analyzes are available, the normalized results of the conclusions would be presented. The activity carried out is included within the CERES project (Advanced Rear End Structural test program), belonging to the Clean Sky 2 Joint Undertaking European research aeronautical program.

Improvement of Natural Fiber Mechanical Properties for Structural Polymer Composites

Improvement of Natural Fiber Mechanical Properties for Structural Polymer Composites

The Influence of Coating and Adhesive Layers on the Mechanical Performance of Additively Manufactured Aluminum–Polymer Hybrid Joints

AddJoining technique has been recently introduced to produce metal–polymer composite hybrid layered structures. The methodology combines the principles of joining and polymeric additive manufacturing. This paper presents three AddJoining process-variants investigated and demonstrated for the material combination aluminum 2024-T3 and acrylonitrile butadiene styrene to form hybrid single lap joints. The microstructure and mechanical performance were assessed. The process variant using heating control showed the ultimate lap shear force of 1.2 ± 0.05 kN and displacement at a break of 1.21 ± 0.16 mm as a result of strong bonding formation at the interface of the hybrid joints. For instance, the other two process variants tested (with epoxy adhesive, and with thin-acrylonitrile butadiene styrene (ABS) coating layer applied on the metal) presented reduced mechanical performance in comparison to process variant using heating control, namely approximately 42% and 8.3%, respectively. The former had a mixed adhesive–cohesive failure due to the lower bonding performance between the adhesive and ABS printed layers. The latter displayed a slight decrease in force in comparison to heat-control specimens. This could be explained by the presence of micro-voids formed by solvent evaporation at the ABS coating layer during AddJoining.

Synergistic effect of h-BN on thermal conductivity of polymer composites

The conductivity characteristics of polymers and polymer composites have become more significant recently. Good heat dissipation is required in many applications, such as circuit boards and heat exchangers, so it is essential to develop the thermal conductivity characteristics of the materials. The micro-fillers have been replaced with nano or hybrid fillers to increase the low thermal conductivity of the polymer. Hexagonal boron nitride (h-BN) and multi-walled carbon nanotubes (MW-CNT), both of which have good conductivity properties, are two popular filling materials. The presence of hydroxyl and amino active groups at the corners of the hexagonal structure of BN improves the thermal conductivity properties of the polymer composite. In addition, it shows high thermal conductivity behavior in polymer composite structures with BN and MW-CNT. It is essential to demonstrate the effects of the volume fraction of additives on the thermal properties of composites with various approaches. In this study, the thermal conductivity behaviors of h-BN/high-density polyethylene and h-BN/MW-CNT/high-density polyethylene composites are demonstrated using the theoretical Bruggeman model, which is based on the assumption that there are constant infinitesimal changes in the material so that there is an interaction between particles. The coefficient of determination (R²) between the thermal conductivity values of the composites and the predictions of the Bruggeman theoretical model is greater than 0.98. This way, the synergetic effect of h-BN and MW-CNT/h-BN additives on thermal conductivity has been theoretically proven.

Sensory methods and machine learning based damage identification of fibre-reinforced composite structures: An introductory review

Fibre-reinforced composite materials are extensively used for manufacturing critical engineering components in diverse applications, which demands intelligent and reliable structural health monitoring (SHM) schemes to prevent catastrophic failures associated with composite structures. Composite materials have complex failure mechanisms, and it is essential to employ reliable SHM methods with high accuracy to detect damages at the incipient stage. Although there are several SHM technologies available, no single strategy is impeccable for tackling all damage types due to the incredibly complex failure mechanisms of the composite materials. Machine learning (ML) methods are frequently integrated to compensate for the limitations of the traditional SHM methods. This paper presents the state-of-the-art sensory methods and deep learning (DL) techniques while emphasizing the future directions for the engineering and scientific community interested in developing novel SHM systems for fibre-reinforced polymer composite structures intended for civil, aerospace, automotive, marine, oil and gas exploration industries.

Preform Porosity and Final Thickness Variability Prediction after Controlled Post-Infusion External Pressure Application with the FEA Model

One of the reasons for the insufficiently wide use of the low-cost and low-labor vacuum infusion process in the production of polymer composite structures is the uneven distribution of pore pressure, porosity, and preform thickness at the final stage of filling the preform with liquid resin. This article presents the results of a theoretical study of the factors that govern the effectiveness of the known method of external controlled pressure on the preform in order to eliminate or significantly reduce the listed disadvantages. The study includes an analysis of scenarios for the implementation of this method, which differ in the state of the resin gate when external pressure is applied to the preform (open or closed), as well as the pressure in the vacuum vent (maintained unchanged or gradually increased to atmospheric pressure). The research tool was a finite element (FE) model that simulates resin flow according to Darcy’s law and controlled boundary conditions for a thin-walled rectangular preform. The results of the study confirmed the effectiveness of the process in achieving a more uniform distribution of porosity and preform thickness and are good qualitative agreement with the results of borrowed experiments, revealing the conditions for the occurrence of critical situations associated with the possible penetration of air into the preforms through the vacuum port and the reverse flow into the preform of the resin previously forced out through the resin gate.

Lightweight and flexible sensors based on environmental‐friendly poly(butylene adipate‐co‐terephthalate) composite foams with porous segregated conductive networks

AbstractConstructing the microcellular structure in the conductive polymer composites (CPCs) is a promising approach to improve the sensitivity and durability of the piezoresistive sensor. Selectively placing the conductive fillers, to form the segregated network between the polymer region, can effectively improve the electric performance of CPCs. However, few researches have focused on the influence of the polymer bead size on the segregated network and the large‐scale production of spherical polymer beads with low cost is still difficult to realize. Herein, plenty of regular‐shaped poly(butylene adipate‐co‐terephthalate) (PBAT) beads were manufactured through underwater pelletizing process, which was further coated with carbon nanotube (CNT) particles with the assistance of ball milling technology, and eventually the sensor was successfully fabricated through supercritical carbon dioxide (scCO2) bead foaming technology. The lightweight and flexible sensor exhibited the uniform cell structure with the mean cell size of 51.0 μm and cell density of 3.9 × 108 cells/cm3 when the pelletizing cutter speed was 2500 rpm and the foaming temperature was 117.5°C. And the conductivity of the sensor reached 6.5 S/m incorporated with 3 wt% CNT, which possessed high sensitivity, good stability and long‐term durability, attributed to its excellent microcellular structure and segregated conductive network.

Modal properties investigation of a carbon/glass fiber-reinforced polymer composite sandwich structure with lozenge-like core: An experimental and finite element simulation

The vibration properties of a carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP) composite sandwich panels with lozenge-like core and free-free boundary conditions are experimentally determined in this research. The sandwich panels manufactured for this study are composed of CFRP, GFRP, and epoxy resin. A modal experiment is performed using a modal hammer with an acceleration sensor to obtain modal properties of the structure, including natural frequencies, damping ratio, mode shapes, and frequency responses. Eventually, the comparison of vibration characteristics of the CFRP sandwich panel with the GFRP sandwich panel with almost identical geometry is discussed in detail. Furthermore, a finite element simulation is developed to validate the precision of the experimental data. It is recognized that the finite element results are in remarkably good agreement with those obtained by modal experiments. Hence, the finite element analysis and experiment method could be utilized to predict the modal properties of the CFRP and GFRP composite sandwich panels.

Influence of curvy stiffeners on the axial crushing response of 3D-printed polymer composite cylindrical tubular structures

Fused deposition modeling, is one of the highly efficient layer-wise additive manufacturing techniques that have shown great prospective in fabricating the energy-absorbing structures as per the designed geometry with appreciable accuracy. In this research study, the axial crushing performance of various polymer and polymer composite-based cylindrical tubular structures with different types of curved stiffeners is investigated experimentally. Four design configurations were proposed for the cylindrical tube with curved stiffeners and all the tubular samples were fabricated through fused deposition modeling-based 3D printing technique. Subsequently, quasi-static axial crushing tests were performed for the successfully fabricated tubes and their axial crushing characteristics were determined and compared. Overall results indicated that the P/CF-CCS1 configuration shows highly improved energy absorption efficiency than the other tube configurations considered in this study. Cylindrical tubes with curvy stiffeners show a more stabilized crushing response with better energy absorption capability in all of the proposed tube configurations.