Carbon Fiber Reinforced Polymer Sandwich Research Articles

Nonlinear dynamic analysis of aircraft CFRP sandwich wings under explosive blast loading: Introducing SVM-DNN algorithm to predict dynamical information

The aircraft wings are a crucial component, particularly during mechanical shock excitation. Thus, for the first time, an inventive adaptable model to simulate the nonlinear dynamics of the wings under explosive blast loading at the moment of the collision is described in this article. It is crucial to increase the structure's stability because of explosive blast loading. The mentioned structure is made of two composite face sheets and a carbon fiber-reinforced polymer (CFRP). Functionally graded (FG) graphene origami (GOri)-enabled auxetic metallic metamaterial (GOEAM) is introduced to improve the stability of this kind of applicable structure, especially in air maneuvers. The analysis is conducted utilizing Reddy's third-order shear deformation of Reddy theory (TSDRT), incorporating Hamilton's principle and Von Kármán nonlinear geometric assumptions. The governing and boundary equations are accurately computed at the domain and boundary edges of the doubly curved structure. The coupled mesh-free radial point interpolation method (MRPIM) and Newton-Raphson method are applied for numerically simulating the current doubly curved structure by employing Newmark's temporal integration method with a constant-average acceleration approach. The present findings are cross-checked against the machine learning method and open-source results from the literature. Based on physical data, machine learning integrates supervised machine learning to predict the nonlinear vibration of the system. In this case, nonlinear transient bending properties are found using hybrid machine learning methods and solutions. The findings demonstrate the significance of GOEAM for nonlinear vibrations of the composite system. The current study's conclusions could be used as a benchmark and useful recommendations for future structural design techniques with enhanced features.

Flexural behaviors and failure mechanisms of CFRP sandwich structures with enhanced dual-phase lattice cores

Inspired by bionic/metallurgical microstructures, novel dual-phase lattice/ Carbon Fiber Reinforced Polymer (CFRP) composite sandwich structures are proposed to improve the energy absorption (EA). The composite sandwich structures for different dual-phase strengthening strategies are designed, where the topology optimization is used to yield efficient lattice distribution configurations. The experimental samples are fabricated by 3D-printing and three-point bending tests are conducted. The flexural failure process and failure modes are observed and analyzed to reveal the failure mechanisms. Results show that DPL-1-CFRP and DPL-2-CFRP have higher peak load (+24.8 % and 18.0 %), post-peak average load (42.6 % and 20.8 %) and specific energy absorption (+7.8 % and + 21.1 %) compared to SPL-1-CFRP. It is indicated that the interactive failure mechanism of dual-phase lattice is effective in improving the mechanical properties of sandwich structure. It represents the occurrence of synergistic deformation between struts rather than a single brittle fracture. Finally, several potential failure mechanisms for the separation of the core and end faces are revealed. This novel concept and structural design greatly contribute to improve mechanical properties of sandwich structure.

An experimental study on the drilling of CFRP sandwich structures with filled and unfilled aramid honeycomb cores

Lightweight carbon fibre-reinforced polymer (CFRP) sandwich structures with honeycomb cores have excellent specific bending stiffness and good dimensional stability; therefore, their future applications will extend extensively, despite their difficult-to-manufacture nature. Although the drilling of single CFRP structures has been widely investigated, the published experience of drilling honeycomb cored CFRP sandwich panels is strongly limited. Therefore, the main objective of the present paper is to experimentally analyse the machinability of CFRP sandwich panels with filled and unfilled aramid Cormaster honeycomb cores through the analysis of thrust force, drilling torque and drilling-induced burrs. A twist and a brad and spur drill were used in two sandwich structures at three feed levels for the drilling experiments. The thrust force and drilling torque were measured by a KISTLER dynamometer, and the burrs were processed through digital image processing of optically captured images. The experimental results show that the application of fillers in the honeycomb only slightly decreases the nominal specific stiffness of the CFRP/honeycomb sandwich structures and slightly increases the thrust force; however, a significant improvement is achievable by their application in the drilling-induced burr formation of the honeycomb core.

Optimization Design of the Bending-Vibration Resistance of Magnetorheological Elastomer Carbon Fibre Reinforced Polymer Sandwich Sheets

An optimization design of the bending-vibration resistance of magnetorheological elastomer carbon fibre reinforced polymer sandwich sheets (MECFRPSSs) was studied in this paper. Initially, by adopting the classical laminate theory, the Reddy's high-order shear deformation theory, the Rayleigh-Ritz method, etc., an analytical model of the MECFRPSSs was established to predict both bending and vibration parameters, with the three-point bending forces and a pulse load being considered separately. After the validation of the model was completed, the optimization design work of the MECFRPSSs was conducted based on an optimization model developed, in which the thickness, modulus, and density ratios of magnetorheological elastomer core to carbon fibre reinforced polymer were taken as design variables, and static bending stiffness, the averaged damping, and dynamic stiffness parameters were chosen as objective functions. Subsequently, an artificial bee colony algorithm was adopted to execute single-objective, dual-objective, and multi-objective optimizations to obtain the optimal design parameters of such structures, with the convergence effectiveness being examined in a validation example. It was found that it was hard to improve the bending, damping, and dynamic stiffness behaviours of the structure simultaneously as the values of design variables increased. Some compromised results of design parameters need to be determined, which are based on Pareto-optimal solutions. In further engineering application of the MECFRPSSs, it is suggested to use the corresponding design parameters related to a turning point to better exert their bending-vibration resistance.

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.

Assessment of high-velocity impact effects on carbon fiber reinforced polymer sandwich panel with M-shaped core reinforced by nano-SiO2: Experimental and numerical study

This paper describes the high-velocity impact behavior of composite sandwich panels with different amounts of nano-SiO2. The sandwich panels were manufactured by carbon/fiber epoxy composite face sheets and an M-shaped core using the vacuum-assisted resin transfer molding method. To enhance the mechanical strength of the matrix, especially impact resistance, the nanoparticles were added to the resin epoxy matrix as filler with the ratios of 1%, 2%, and 3% of the composite's total weight. A scanning electron microscope was utilized to observe the microscopic structure of the composites, and it revealed an exceptional homogeneous mixture of nano-SiO2 particles in the resin epoxy matrix. Afterward, high-velocity impact tests were carried out using a single-stage gas gun test machine. A spherical steel projectile with a diameter of 8.7 mm was used for the test with a speed of 235 m/s. The experimental results indicated that adding 1–3 wt% of nano-SiO2 into the matrix remarkably increased the impact resistance of the composite. Moreover, the results showed that when the projectile collides with the core of the sandwich panel, it remains in the sandwich panel and its output velocity becomes zero, while when the projectile does not collide with the core, its output velocity is not zero. In order to validate the results, the experimental data were compared to the finite element models, and good agreement was observed.

Mechanical behaviors and fracture mechanisms of CFRP sandwich composite structures with bio-inspired thin-walled corrugated cores

This paper investigates mechanical behaviors and fracture mechanisms of bio-inspired thin-walled corrugated-core sandwich composite structures made of carbon fiber-reinforced polymer (CFRP) under four-point bending and flatwise compression. Biomimetic thin-walled corrugated cores, inspired by nature's structures, were proposed and manufactured using the hot vacuum molding method. Quasi-static bending and compression tests were conducted to characterize the load capacity, compressive strengths, and failure progressions with the assist of the digital image correlation and thermography method. Measured full-field strains revealed critical bending/compression strains of the samples while a temperature increase was observed in full-field thermal maps, which was a sign of crack initiation. We concluded that the fracture mechanisms of specimens in bending tests depend on the fiber orientations of the core. The sandwich structure with a core angle of ±45 degrees exhibited a larger load capacity and bending stiffness than the structure with a core angle of 0/90 degrees. The cracks were mostly initiated at the core (0/90 degrees) and the facesheet (±45 degrees) with a core crushing and facesheet fracture, respectively, and propagated in the core with shear cracks due to fiber fractures. In addition, the failure of the thin-walled corrugated cores in flatwise compressions arose first by buckling and was followed by the subsequent collapse of the cores. The theoretical calculation provided a useful understanding of the different failure mechanisms of the sandwich structure. The proposed sandwich structures achieved prominent mechanical performances that were 26.5 MPa/gcm−3 in bending and 11.8 MPa/gcm−3 in compression and the experimental technique can depict the successive events that lead to the complex fracture of thin-walled corrugated core sandwich composites.

Manufacture of braided-textile reinforced multi-walled tubular structures and axial compression behaviors

Carbon fiber reinforced polymer (CFRP) thin-walled tubular structures have been widely used in lightweight energy absorbing components. In this paper, CFRP tubular braided-textiles, foam-filling technique, and sandwich structure were applied to make low-cost multi-walled sandwich tubular structures. Through axial compression tests, the compression behaviors, crushing modes and energy absorption performance of the braided-textile reinforced multi-walled sandwich tubes were contrastively analyzed. Experimental results show that the foam-filling technique and the sandwich structure are both effective in modifying the crushing patterns and improving the energy absorption efficiency. Especially for the multi-walled sandwich structure, it can increase the specific energy absorption (SEA) by at least 66% and change the crushing mode from local bucking to progressive diamond folding.

Influence of multi‐walled carbon nanotubes reinforced honeycomb core on vibration and damping responses of carbon fiber composite sandwich shell structures

AbstractIn the present study, vibration and damping characteristics of the multi‐walled carbon nanotubes (MWCNT) reinforced honeycomb embedded sandwich composite shell structures have been investigated numerically using finite element (FE) method. The efficacy of the FE method by deriving the governing equations using higher order theory is verified by comparing the natural frequencies assessed using ABAQUS 3D FE model. The influence of MWCNT reinforcement, support condition, and radius of curvature on the dynamic performance of honeycomb sandwich shell with carbon fiber reinforced polymer (CFRP) composite face sheets are explored. In addition, the optimal ply orientations of the various configurations of CFRP sandwich shells with MWCNT/GFRP honeycomb are identified using the developed FE model coupled with genetic algorithm (GA) to enrich the natural frequencies and loss factors. Further, it can be observed that the reinforcement of MWCNTs in honeycomb core, geometry of shell structure, and optimal ply orientations significantly influences the natural frequencies and loss factors of the sandwich composite shell structures.

Low-velocity ice impact response and damage phenomena on steel and CFRP sandwich composite

This study investigates the low-velocity impact (LVI) response of ice impactor on steel and carbon fiber reinforced polymer (CFRP) sandwich composite. This research explores the effect of impactor's shape and length at different impact velocity by preparing customized conical and cylindrical ice impactors. Ice impactors that are frozen at -12 °C for 48 h are found to have the highest occurrence of partial damage, while ice impactors conditioned at -22 °C for 72 h experienced full damage. Although higher peak force is observed during ice-steel interaction, greater displacement and absorbed energy are evident in ice-composite impact. Results also show that full damage of ice impactor is more prominent for sandwich composite specimens, while partial damage is commonly seen in steel specimens. This is attributed to multiple hits and higher ratio of collision velocity during impact on sandwich composite. Damage type occurrences also vary depending on shape, length, and impact velocity of the ice impactors. Presence of pre-existing cracks during freezing as well as variation in stress level at the impact region influence the strength of the ice impactors. Matrix crack and facesheet dent are observed as the dominant damage mechanism in composite using X-ray micro-computed tomography. Different ice fragmentation processes are also characterized in this study.

Flexural strength of foam‐filled polymer composite sandwich panel with novel M‐shaped core reinforced bynano‐SiO2

AbstractPresent article has experimentally determined the flexural strength of carbon fiber reinforced polymer sandwich panel reinforced by nano‐SiO2with novel M‐shaped lattice core. For this purpose, a polymer composite sandwich panel with M‐shaped core made of carbon‐epoxy fiber has been fabricated in this experiment. In order to fabricate the sandwich panels, the vacuum assisted resin transfer molding has been used to achieve a laminate without any fault. Afterward, polyurethane foam (PU) has been injected into the core of the sandwich panel. In order to determine the flexural strength of the sandwich panels, they have been subjected to three‐point bending loads. From the results of the study, it was figured out that: a) Adding 1 to 3 wt% of nano‐SiO2into the carbon fiber had the most desirable effects on the enhancement of flexural strength of the sandwich panels. b) PU has improved the flexural strength of sandwich panels. c) The new M‐shaped core can well postpone the buckling and failure of the composite sandwich structures.

A Bayesian probabilistic approach for damage identification in plate structures using responses at vibration nodes

Structural health monitoring for plate structures is important since they are essential structural components in many applications. One interesting topic for structural health monitoring methods is to achieve accurate damage detection with a small number of sensors and without the requirement of a high-fidelity finite element model. Traditional damage detection techniques for plates need many sensors to be distributed on the surface of the plate. This paper adopts dynamic responses at a few vibration nodal points combined with a Bayesian probabilistic approach for damage identification in plate structures. Vibrational amplitudes at nodal points, also referred as node displacement or NODIS, have the potential to achieve real-time damage assessment with a relatively small number of sensors. Thus, they can serve as efficient structural damage indicators. Despite these advantages, this method has not been applied to plate-type structures. This paper proposes a vibration-based SHM method for plates that is suitable for real-time monitoring, requires a small number of industrial sensors, does not rely on a high-fidelity FE model and can be applied for damage assessment of location and severity. In the Bayesian framework, an efficient perturbation-based surrogate model is derived for plate structures to replace the expensive FE model. The accuracy of the perturbation-based surrogate model is investigated and compared with FE results. Then, this paper evaluates the performance of the NODIS-based Bayesian framework with the perturbation method by comparing it with FE results. At last, the proposed method is applied to a carbon fiber reinforced polymer sandwich structure with different grinding depths.

Materials Selection Methods in the Design of Monocoque for a Fuel Efficient Concept Vehicle

A multiple criteria decision methods (MCDM) using Complex Proportional Assessment (COPRAS), Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), and Cost per Unit Property were utilized to determine the best material in the design of monocoque for a fuel efficient vehicle. Specifically, the material properties being evaluated from the different alternative materials for the floorboard and body of an urban concept eco-car underwent necessary calculations based on the integration of the various material selection methods. The study showed that the glass fiber-reinforced polymer (GFRP) was the best floorboard material among other options from magnesium alloys, aluminium alloys, mild steel and carbon fiber-reinforced polymer (CFRP). The criteria considered in the calculation include the ultimate strength, yield strength, modulus of elasticity, density and cost. Moreover, the face sheet CFRP and honeycomb core sandwich combination, particularly the T700-Nomex honeycomb, was the best option for the car body. The properties being considered in this calculation were the maximum in plane stress (MIPS) of the face sheet material, the maximum shear stress of the core, the weight and the cost.

3D printing of composite sandwich structures using continuous carbon fiber and fiber tension

Many modern aircraft components are made from carbon fiber reinforced polymer sandwich structures with two outer skins possessing high tensile and compressive strengths separated by a lightweight core that provides shear stiffness. However, the conventional manufacturing method involves a complicated and costly bonding process. This study used a continuous carbon fiber 3D printer to manufacture sandwich structures with honeycomb, rhombus, rectangle, and circle core shapes as a single piece. The functional properties of the sandwich structures were quantified by shape evaluations and three-point bending tests. Three-point bending tests showed maximum load and flexural modulus increased as effective density increased for all core shapes, but the rhombus core shape was the strongest. Because the mechanical properties depended on the core shape, continuous carbon fiber 3D printers can be used to flexibly design core shapes that satisfy the desired strength and stiffness.

Novel development of dynamic behavior of carbon fiber reinforced polymer sandwich panels with stepwise graded adhesive layer

Purpose The purpose of this study is to focus on the developments of carbon fiber reinforced polymer (CFRP) panels with stepwise graded properties on adhesive layer. The various arranges of the graded properties of the adhesive layer have been checked according to experimental results of the literatures and based on applicability. Design/methodology/approach The finite element (FE) models and experimental modal tests of the manufactured CFRP sandwich panel specimens have been investigated. The core thickness, core density and orientation of the fiber direction of the sandwich panel face – sheets have been parametrically checked based on modal behavior. Two fully free and fully clamped boundary conditions (BC) have been checked in stepwise graded adhesive zone (SGAZ) cases and first five non-zero natural frequencies (NF) have been compared. Dynamic response of the SGAZ includes modal analysis and transient dynamic loading have been performed numerically with ABAQUS 6.12 well-known FE code. Findings The first non-zero NF of SGAZ Case 4 was 11.69 per cent higher than homogenous Case 2 and 7.06 per cent lower than Case 1 in fully free boundary conditions. A total of 26.38 per cent is the greatest discrepancy between fist five non-zero NFs of all cases with two BCs (Case 1 vs Case 2 in fully clamped BC). Maximum structural damping behavior and minimum stress picks have been studied during transient dynamic loading analysis of CFRP panel with SGAZ. SGAZ Case 3 (middle adhesive with lower modulus) has increased the maximum structural damping while reducing the minimum out of plain tip displacements during transient dynamic loading by 111.26 per cent in comparison with homogenous Case 2. Also, Case 3 has reduced the Mises stress picks on the adhesive region by 605.68 per cent. Practical implications Making a stepwise graded adhesive region (without any added mass) has been shown that it is a novel and useful way to achieve a wide range of stiffness on CFRP panels. Originality/value Development of the sandwich panels with various stiffness and damping properties.

Compressive strength after blast of sandwich composite materials

Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene–acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3 m sized panels were subjected to blast of a Hopkinson–Cranz scaled distance of 3.02 m kg−1/3, 100 kg TNT equivalent at a stand-off distance of 14 m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411–413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast.

Experiment Study and Numerical Simulation of CFRP Sandwich Structure on Aircraft Ditching Model

This paper do the research of molding process, experimental study, numerical simulation for carbon fiber reinforced polymer (CFRP) sandwich structure under an aircraft ditching model. The model is simultaneous restricted to the weight and strength requirements. Choosing three types of expandable polystyrene (EPS) foam, testing their properties in different kinds of conditions: density, thickness of the core, layer. By the experiment to verify the design, we can gain the optimized layer, thickness of the core and parameters. This project can provide the basis to the design of manufacturing, process parameters and weight control for CFRP sandwich structure on aircraft ditching model.

Mechanical behaviour of CFRP sandwich structures with tetrahedral lattice truss cores

A method of manufacturing carbon fibre reinforced polymer (CFRP) tetrahedral lattice truss core sandwich structure by thermal expansion silicon rubber mould was developed. The sandwich structure was manufactured integrally without secondary bonding and the silicon rubber mould can be made mass-production with low cost in this approach. The intrinsic property of the CFRP was fully exploited because of carbon fibres aligned in the axial orientation of the truss member. The mechanical properties of CFRP tetrahedral lattice truss core sandwich structures were investigated by flatwise compression and shear test. The experimental results indicate that CFRP tetrahedral lattice truss core sandwich structures have higher weight-specific compressive strength than some metal truss cores, and are competitive with conventional honeycombs.