Carbon Fiber Composite Sandwich Research Articles

Experimental study on compression properties of composite aluminum honeycomb sandwich structures

AbstractThe mechanical properties of the carbon fiber and glass fiber composite honeycomb sandwich structure were studied through compression experiments. The influence of different aluminum honeycomb edge lengths, upper and lower panel thickness, aluminum honeycomb thickness, and loading speed on the compression failure load of carbon fiber composite laminates sandwich structure is analyzed. The influence of different aluminum honeycomb edge lengths and thicknesses on the compression failure load of glass fiber composite laminates sandwich structure was studied. The results show that the thickness of the panel has a significant effect on the failure load of the carbon fiber composite laminate sandwich structure, and the loading speed has a significant effect on the failure load of the carbon fiber composite laminate sandwich structure. The greater the loading speed, the greater the value of the failure load. The edge length and thickness of the aluminum honeycomb have a certain effect on the damage load of the carbon fiber composite laminates sandwich structure, but the influence on the mechanical properties of the glass fiber composite laminates sandwich structure is much greater.Highlights The compression performance of composite sandwich structures was experimentally studied. The influence of composite panel thickness was studied. The influence of aluminum honeycomb edge length and thickness was studied. The influence of loading speed was studied.

High‐velocity impact resistance of the carbon fiber composite grid sandwich structures

AbstractThe carbon fiber composite grid sandwich structure represents an innovative category of lightweight composite sandwich structures, showcasing remarkable attributes including reduced weight, high‐specific strength, exceptional specific stiffness, and robust design flexibility. Using ABAQUS, the high‐velocity impact performance of carbon fiber composite grid sandwich structure is numerically simulated. This study delved into examining the impact patterns arising from various factors, including the equivalent density, height, and geometric configuration of the core layer. Additionally, the effects of the impact punch's initial velocity, size, and impact position on the high‐speed impact resistance performance of the carbon fiber composite grid sandwich structure were explored. The fracture absorption work of the structure and the kinetic energy attenuation rate of the impact punch are positively correlated with the equivalent density, height of the structural core layer, as well as the initial velocity and dimensions of the impact punch. Notably, the square carbon fiber composite grid sandwich structure was most significantly influenced by the equivalent density of the core layer, while the mixed carbon fiber composite grid sandwich structure was most sensitive to variations in core layer height and punch size. When impacted at the intersection of the ribs, compared with the central position between the two ribs, the structure shows enhanced fracture absorption energy and greater impact kinetic energy attenuation rate.Highlights The structure was modeled based on the interlocking assembly process. The high‐velocity impact resistance of the structure was studied. Different structural parameters were designed for the core layer to study. The initial velocity, size and impact position of the punch were involved.

Free vibration behaviours of composite sandwich plates with reentrant honeycomb cores

The free vibration behaviours of carbon fiber composite sandwich plates with reentrant honeycomb cores were explored by experiment, theory and finite element method (FEM) in present study. The composite sandwich plates with reentrant honeycomb cores were designed and fabricated through hot-press and secondary forming technology. The modal characteristics of composite auxetic honeycomb sandwich plates were tested under simply supported boundary conditions. Furthermore, the influences of relative densities and dimensions on the natural frequencies of composite auxetic honeycomb sandwich plates were studied. The equivalent moduli of the unit cell of reentrant hexagonal core were deduced. The free vibration control equation was derived to gain the natural frequencies of the sandwich plates by Zig-Zag theory. The theoretical results of the natural frequencies were obtained and compared with the experimental results and finite element calculation results. The results showed that the theory and FEM could estimate the natural frequencies of this kind of sandwich plates accurately. The natural frequencies of the sandwich plates raised as the increasing of relative densities and influenced by dimensions of the core.

Mechanical behaviors of the carbon fiber reinforced X-core sandwich structure under the dynamic compression

A split Hopkinson pressure bar technique was applied to investigate the dynamic response of carbon fiber composite sandwich structures with the X-cores. The compressive mechanical behaviors of the composite X-core unit cells and its foam reinforced unit cells at the strain rates ranging from 3•10−4 s−1 to 600 s−1 were obtained. During the dynamic tests, the dynamic stress equilibrium state in the unit cells was achieved by adopting the pulse sharpers and discussed comprehensively. The measured structural strength increased by 81.9 % on average at the high strain rates than that under the quasi-static compression. Under the dynamic compression, the failure modes captured by a high-speed camera were found similar with that of the quasi-static tests. Finite element analysis was utilized to study the variation history of stress and strain rate fields of the core. Because of the material failure strain enhancement effect, the experimental and simulated compressive strength of the composite unit cells both increased significantly at the high strain rates. At the same high-speed compressive strain rate, the dynamic reinforcement effect of the composite sandwich unit cell was smaller than that of the parent material.

The design of continuous carbon fiber composite honeycombs and study on its properties

A lot of researches on continuous carbon-fiber composite laminates have been conducted, but no scrutiny has been devoted to continuous carbon-fiber composite honeycomb sandwiches. This paper is aimed to assess the design and properties aspects of honeycomb sandwiches made of continuous carbon-fiber composite laminates. The applicability of the existing theoretical formulas for the mechanical properties of isotropic material honeycomb sandwich on continuous carbon-fiber composite honeycomb is examined by comparing the obtained results from the finite-element modeling and experimental results. The results reveal that the theoretical formulas of isotropic material honeycomb sandwich in density and out-of-plane compressive elastic modulus are suitable for continuous carbon-fiber composite honeycomb, while other performances cannot be achieved by theoretical formulas of isotropic material honeycomb sandwiches. The out-of-plane compression and shear properties of continuous carbon-fiber composite honeycomb can be evaluated by finite-element modeling. The effects of cell side length, wall thickness, and 45° ply content on the honeycomb density, out-of-plane compression properties and out-of-plane shear strength are researched. Subsequently, the out-of-plane compression experiments of honeycomb are carried out to show the accuracy of the finite-element modeling. Finally, a design approach for continuous carbon-fiber composites honeycomb structures is proposed. This methodology results in the design of honeycomb sandwiches with better performances. The chief innovation of this paper is to develop the concept of continuous carbon-fiber composite honeycomb sandwich structures. To this end, a honeycomb structure finite-element model of continuous carbon-fiber composite is established, and the mechanical properties of continuous carbon-fiber composite honeycomb sandwiches are explored. A methodology for the rapid design of honeycomb size parameters of continuous carbon fiber composite honeycomb sandwich is also proposed.

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.

Failure of carbon fiber composite sandwich cylinders with a lattice core under axial compressive loading

Sandwich cylinders with a low-density pyramid-like truss core made of plain-woven carbon fiber fabrics are manufactured using a sequential hot press method. Then, the structural compressive strengths corresponding to four possible failure modes (Euler buckling, axisymmetric buckling, local buckling and face panel crushing of the sandwich cylinders) are obtained by theoretical analysis. The 3D failure mechanism map is accordingly generated to guide the design and preparation of the cylinder specimens. Thereafter, axial compressive tests are performed on the specimens to investigate the failure mechanisms of these structures and to validate the theoretical predictions. The errors between theoretical and experimental results, including both the axial compressive ultimate loads and failure modes, are acceptable. The developed 3D failure mechanism map provides an intuitive guide for the design of sandwich cylinders with a pyramid-like lattice truss core against buckling failure.

Investigation of carbon nanotube reinforcement to polyurethane adhesive for improving impact performance of carbon fiber composite sandwich panels

In this study, the development of a polyurethane adhesive by using carbon nanotubes (CNT) to enhance the low-velocity impact behavior of aluminum honeycomb sandwich composite structures was investigated. The interaction of CNT and polyurethane for the impact behavior of sandwich composite panels is the main originality of this paper. The fabrication of carbon fiber reinforced composite (CFRC) sandwich structures was conducted using different polyurethane (PU) adhesives and different honeycomb cell sizes. CFRC sandwich structures were fabricated with multi-walled carbon nanotube (MWCNT) added and neat PU adhesives, 6.78 and 10.39 mm honeycomb cell sizes, and carbon fiber prepregs. Neat and nanotube added PU adhesives with MWCNT at reinforcement of 0.1% and 0.2% by weight percent were prepared. Sandwich composite panels were manufactured using the hot pressing method. Specimens of 100 × 100 mm were cut from the sandwich panels, and low-velocity impact tests were conducted at 100 J initial impact energy according to ASTM D7136 standard. After experiments, load-deflection curves, load-time, and energy-time histories were acquired. The absorbed energy values at maximum load were evaluated as a function of MWCNT content and honeycomb cell size. Specimens were sectioned from the impacted region and scanned using scanning electron and optical microscopes to analyze the damaged area. Specimens with MWCNT reinforced adhesives carried higher maximum loads compared to neat ones. CFRC sandwich structures with MWCNT added PU adhesives exhibited a 6% higher impact resistance at 100 J energy levels. Experimental results demonstrated that an increase in MWCNT loading and a decrease in PU adhesive cell size increased the maximum load values in CFRC sandwich panels. Among the nanotube added adhesives, 0.1 wt percent showed the best impact performance.

Preparation and sound transmission loss analysis of carbon fiber composite sandwich panel

Preparation and sound transmission loss analysis of carbon fiber composite sandwich panel

High-force dynamic mechanical analysis of composite sandwich panels for aerospace structures

High-force dynamic mechanical analysis (DMA) has enabled the non-destructive evaluation of thermo-mechanical properties for highly stiff structures over a range of loading frequencies, allowing for additional insight not provided by commonly used static and impact test procedures. In this study, carbon fiber composite sandwich panels with both aluminum and aramid honeycomb cores are characterized based on application conditions in the airframe structure of a high-performance two passenger aircraft. The relative stiffness and damping ability across critical flight frequencies (1 – 100 Hz) for different panel cores are compared. It is found that the damping of the composite sandwich panels is dependent on the applied static load as well as the core material used. Temperature sweeps are also conducted and found to be capable of detecting differences in the glass transition temperature of the composite face sheet matrix material based on post-curing procedures of the manufactured panels.

Investigation on the shear behaviors of carbon fiber composite sandwich panels with the X-core

In-plane shear response of an all-composite X-core sandwich panel was investigated experimentally, numerically and analytically in this paper. The shear experiments of the X-core sandwich panels with three different relative densities were performed and the delamination on the joint and web was the dominant failure mode. Finite element analysis were conducted to further investigate the large deformation and progressive failure of the X-core sandwich panels under in-plane shear loading. The numerical models can correctly simulate the initiation and extension of the delamination and the predictions for the shear response were in good agreement with experiments. A theoretical model based on a modified Reddy zig-zag laminated beams theory and a spring model for the joint were employed to forecast the shear mechanical properties. The analytical results indicated the member shear deformation and joint stiffness had significant effects on the shear modulus and had a reasonable agreement with the experimental results.

The three-point bending responses of carbon fiber composite sandwich beams with Y-frame cores at high and low temperatures

An experimental investigation was performed to explore the effects of the temperature on the three-point bending properties and failure mechanisms of carbon fiber composite sandwich beams with Y-frame cores in this paper. The composite sandwich beams with Y-frame cores firstly were fabricated using hot-press method. Subsequently, the three-point bending experiments of composite sandwich beams were tested at eight selected temperatures which ranged from -70 °C to 200 °C. Then the effects of temperature on the bending load–displacement curves, failure mechanism and bending failure load were analyzed and discussed. The experimental results showed that the bending load–displacement curves went down as temperature increased. The fiber fracture occurred for the specimens at temperature below the glass transition temperature, while the fiber microbuckling was observed for the specimens at temperature above the glass transition temperature. In addition to the change of load–displacement curves and failure modes, the bending failure load and the value of PT∕δT decreased as temperature increased. Finally, the analytical model of bending failure load and the value of PT∕δT for the composite sandwich beam was presented. The analytical predictions were calculated and compared with experimental results.

Modal response and vibration attenuation of carbon fiber composite sandwich cylindrical panels made of bi-directional corrugated strip cores

To explore desirable structures with both higher fundamental frequency and better vibration suppression, we designed and fabricated carbon fiber composite bi-directional corrugated sandwich cylindrical panels (BCSCPs) by a hot press molding and post-assembly approach. Modal response and vibration attenuation performance of such structures were investigated experimentally and numerically. Furthermore, the free and forced vibration responses of simple laminated cylindrical panels (SLCPs), axial corrugated sandwich cylindrical panels (ACSCPs) and circular corrugated sandwich cylindrical panels (CCSCPs) with almost the same relative density were investigated and compared with that of BCSCPs. The results indicated that the numerical models were reasonable to estimate the vibration properties of BCSCPs, and the vibration attenuation performance can be improved by suitably increasing the thickness of face sheet and bi-direction corrugated core. Besides, it was revealed that the BCSCPs, ACSCPs and CCSCPs all had comparatively better vibration attenuation performance than that of the SLCPs, and the present BCSCPs generally had higher natural frequencies than those of the ACSCPs and CCSCPs with almost the same weight, which may provide some references for further engineering application of such kinds of composite sandwich structures.

Failure analysis and bending performance of carbon fiber composite sandwich structures with corrugated cores

In recent years, composite materials have been more widely used in sandwich structures, which have been proved better performance in sandwich structures than other materials in some cases. In this paper, an analytical model is developed to predict the key stress, failure modes, and failure loads of the composite corrugated-core sandwich structures under three-point bending in both longitudinal and transverse directions. Then a three-dimensional finite element model by using Hashin’s model to predict fiber composite laminates and cohesive zone model to predict extra epoxy layer of fiber composite laminates is developed and validated by the corresponding experiments. The analytical model is also validated through both simulation and experiment. Finally, the failure mechanism maps and effects of orientation angles on failure have been further studied based on the analytical model.

Temperature effects on the compressive properties and failure mechanisms of composite sandwich panel with Y-shaped cores

The effects of temperature on the mechanical properties and failure mechanisms of composite sandwich panel with Y-shaped cores under out-of-plane compression have been studied in this paper. The carbon fiber composite sandwich panel with Y-shaped cores was manufactured by a hot-press method using unidirectional carbon/epoxy prepregs. The out-of-plane compression tests of composite sandwich panels were conducted at temperatures ranging from 20 °C to 200 °C. Then the stress-strain curves, failure modes, compressive stiffness and strength of composite sandwich panel at high temperatures were analyzed and compared with those ones at room temperature. The results have shown that temperature had a significant effect on mechanical properties and failure behaviors of composite sandwich panel. And high temperature resulted in the decreasing of compressive stiffness and strength. Finally, the analytical expressions were presented to predict the compressive stiffness and strength of composite sandwich panel and compared with experimental results at different temperatures.

Compressive and shear properties of carbon fiber composite square honeycombs with optimized high-modulus hierarchical phases

This paper focuses on strengthening carbon fiber hierarchical composite square honeycomb structures (HCSH) by selecting high-modulus hierarchical phase and optimizing its thickness. HCSH have been manufactured from carbon fiber composite foam sandwich structures by a simple snap-fit and bonding method. The measured compressive and shear strengths are shown to be well predicted by micromechanics failure models of HCSH. Compared to the monolithic composite square honeycomb structures (CSH), the measured specific out-of-plane compressive strength of HCSH improves to approximately 330% and the specific shear strength improves to about 180%. Furthermore, the relationships between hierarchical phase modulus and its optimum thickness are developed to design the optimum HCSH. Carbon fiber HCSH are found to exhibit better mechanical properties than other cellular structures, and thus provide new opportunities for light-weight multifunctional sandwich structures.

Experimental and numerical study on the modal characteristics of hybrid carbon fiber composite foam filled corrugated sandwich cylindrical panels

To further improve the vibration damping behavior of carbon fiber composite sandwich structures without too much redundant weight, empty and foam filled corrugated sandwich cylindrical panels (CSCPs) are designed and their corresponding modal characteristics are investigated experimentally and numerically. Axial and circular CSCPs (ACSCPs and CCSCPs) are simultaneously manufactured by a hot press moulding and post-assembly approach. It has been demonstrated that foam filled CSCPs can obviously improve the structural damping compared to the empty CSCPs without significant change of the corresponding natural frequencies. Furthermore, validated finite element analysis (FEA) models are adopted to systematically study the effects of the corrugated inclination angle, sandwich core thickness, arc-length and topological corrugated configurations on the modal properties. Several conclusions are drawn, which may be useful for the multifunctional design of such kinds of composite sandwich structures.

Compression and shear response of carbon fiber composite sandwich panels with pyramidal truss cores after thermal exposure

ABSTRACTThe composite pyramidal truss core sandwich panels with reinforced joints are manufactured by the water jet cutting and interlocking assembly method. The effect of thermal exposure on the out-of-plane compression and shear performances of composite sandwich panels is investigated experimentally. In particular, the out-of-plane compression and shear moduli and strengths of the structures after thermal exposure are predicted theoretically. Experimental results show that the out-of-plane compression and shear performances of composite pyramidal truss core sandwich panels first increase and then decrease with thermal exposure temperature at the thermal exposure of 6 h. The failure modes depend on the particular temperature and time of the applied thermal exposure. As well, the compression and shear performances first increase and then decease with thermal exposure time at 150°C. However, their compression and shear performances have a decreasing tendency with time for a given 230°C exposure temperature. In addition, the destruction responses of composite sandwich panels are also investigated and their possible failure modes (including the crushing, delamination and local buckling of struts) are complemented with the analytic results.

Influence of manufacturing defects on modal properties of composite pyramidal truss-like core sandwich cylindrical panels

Defects can easily appear in composite lattice truss core sandwich structures during the complex preparation process, which may significantly affect the structural response and decrease the load-carrying capability. The purpose of this paper is to investigate the manufacturing defect sensitivity of modal vibration responses of carbon fiber composite pyramidal truss-like core sandwich cylindrical panels by modal experiments and finite element analysis. Defects including debonding between face sheets and truss cores (DFT), truss missing (DTM), face sheet wrinkling (DFW) and gap reinforcing (DGR) are introduced into the present intact specimen artificially and modal testing is conducted to study their dynamic behavior under free-free boundary conditions. Finite element models consistent with the experiments are then developed to further study the effect of defect extents, locations and forms on the modal parameters of the present sandwich cylindrical panels. Results indicate that the degree of sensitivity of natural frequencies of the present sandwich cylindrical panels mainly depends on the vibration modes, defect extents, locations and forms. In addition, damping loss factors are much more sensitive than their corresponding frequencies. Some conclusions and essential mechanisms are summarized, which is helpful to vibration-based non-destructive evaluation (NDE) of such kind of composite lattice sandwich structures.

Analysis of Energy Density Spectrum of Lowvelocity Impact in Honeycomb Sandwich Panel with FBG

As a kind of structure commonly used in satellite, carbon fiber composite honeycomb sandwich panels are vulnerable to various kinds of damage, especially low-velocity impact damage in the process of using. In this paper, an impact monitoring system based on Fiber Bragg Grating (FBG) sensor is constructed. The frequency domain information of the signal can be obtained by Fourier transform. Monitoring results of different impact points show that the natural frequency of structure is 110Hz and 380Hz, which amplitude of different natural frequency is changed with position of impact point. The energy status of impact response signal can be obtained by wavelet packet analysis. The monitoring results of the same impact point shows that the change of the sensor signal is obvious in thirteenth order and energy size is related to the distance and angle between the impact point and sensor.