Fiber-reinforced Composite Panels Research Articles

Influence of Nanodiamonds on Mechanical, Acoustic, Vibration Damping and Flame Retardancy in Jute Fiber-Reinforced Epoxy Composite Panels Used in Indoor Applications

Influence of Nanodiamonds on Mechanical, Acoustic, Vibration Damping and Flame Retardancy in Jute Fiber-Reinforced Epoxy Composite Panels Used in Indoor Applications

Study on the trouser tearing characteristics of airship skin film materials

Abstract In this paper, the tearing properties of Kevlar fiber-reinforced lightweight composite panels are thoroughly investigated through a combination of experimental and theoretical analysis. The research focuses on the tearing strength of airship skin materials, especially on the trouser-tearing behavior of Kevlar materials. By establishing a physical model of a “triangle-like region”, the change of material morphology during trouser tearing is analyzed, and a quadratic model is proposed to describe the tensile elongation of the weft yarn bundle. In the experimental part, the model’s accuracy was verified by the trouser tearing test, and the elastic modulus of the skin material was calculated by generating the tensile force-displacement curve with super test software. The test results show that the material’s maximum tensile load capacity and minimum tensile load capacity. Eventually, by comparing the experimental data with the simulation results, the validity of the established physical model is verified, which provides an important reference for the design and selection of the skin material of the airship.

Compression after impact (CAI) failure mechanisms and damage evolution in large composite laminates: High-fidelity simulation and experimental study

This study focuses on developing and validating a high-fidelity finite element model for predicting damage evolution and residual strength in fiber-reinforced composite panels. Impact and compression after impact (CAI) tests were conducted at both barely visible impact damage (BVID) and clearly visible impact damage (CVID) levels. The ASTM D7137 standard 100 mm × 150 mm CAI coupons were inadequate to cover the range of experimental studies required for model validation. Therefore, larger 254 mm × 304.8 mm laminates were investigated under two CAI testing conditions: one a scaled-up version of ASTM standard coupon, and the other with additional anti-buckling support plates to reduce unsupported areas to 127 mm × 177.8 mm. The model captured inter- and intra-laminar failure modes, including fiber breakage, splitting, kinking, pull-out, and crushing as well as matrix cracking, delamination, and their interactions. This was achieved by cohesive zone modeling technique and enhancement of the LaRC05 failure criteria through modeling the fiber damage evolution and utilizing an efficient search algorithm to determine the matrix fracture plane and fiber kink band angle. This study underscores the efficacy of the high-fidelity modeling approach in accurately predicting both impact damage and CAI strength in typical aircraft impact damage scenarios. Additionally, it provides insights into complex CAI failure mechanisms and energy release associated with various damage modes and highlights the effect of global buckling on the failure behavior and compressive strength of composite laminates. Furthermore, it shows that the proposed fixture with support plates is suitable for testing a broader range of impact scenarios without experiencing global buckling.

Transient Aerodynamic Heating Effects on Aeroelastic Dynamic Response of Curved Fiber-Reinforced Composite Panel in Supersonic Airflow

The nonlinear aero-thermo-elastic behaviors of the curved-fiber composite panel are studied accounting for transient aerodynamic heating effects with two-way coupling method. The Von Karman assumption is utilized to depict the large deflection of the composite panel and the supersonic aerodynamic load is incorporated through first-order piston theory, respectively. The aerothermal and aeroelastic models are coupled with each other by performing the iterative procedure in the time domain. The aerodynamic heating heat flux is obtained by the Eckert reference temperature method, the transient temperature field is solved by the finite difference method, and the aeroelastic dynamic response is solved by the combination of the Newmark method and Newton–Raphson method. The accuracy and validity of the established model are justified by comparing the present solutions with the present numerical results in published literature. Then, the influences of the key parameters such as the transient temperature field, coupling step, heat transfer coefficient, shock wave, initial disturbance force and fiber configurations on aerothermoelastic responses of the composite panel respectively are discussed in detail.

Experimental study on fiber-reinforced ceramsite concrete composite wall panel and correction of seismic damage model

In order to study the damage model of the new fiber-reinforced ceramsite concrete composite wall panels under seismic action, two groups of six wall panels are subjected to seismic tests. The failure mechanism, hysteresis and skeleton, load-bearing capacity, energy dissipation, stiffness, and other seismic indicators are analyzed. The test results show that the displacement angle of the new composite wall panels is greater than the limit of ordinary shear walls. The ratio of ultimate displacement angle to yield displacement angle is approximately 3, indicating a high ductility and strong deformation capacity of the wall panels. The comprehensive indicators show that both types of wall panels exhibit excellent seismic performance. By utilizing analytical tools to simulate and analyze two types of wall panels, the calculated results demonstrate a small error compared to experimental results, confirming the accuracy of the computational model. Building upon experimental results and previous research findings, this study proposes a seismic damage model suitable for new composite wall panels and further defines the damage indicator range of the model. Through example applications and comparative analysis of effects, the correctness and universality of this damage model are proven. The seismic damage model presented in this study not only improves upon the Park-Ang damage model but also enriches the types of damage assessment for wall panel components.

A shield of defense: Developing ballistic composite panels with effective electromagnetic interference shielding absorption

The primary goal of this study is to develop cost-effective shield materials that offer effective protection against high-velocity ballistic impact and electromagnetic interference (EMI) shielding capabilities through absorption. Six fiber-reinforced epoxy composite panels, each with a different fabric material and stacking sequence, have been fabricated using a hand-layup vacuum bagging process. Two panels made of Kevlar and glass fibers, referred to as (K-NIJ) and (G-NIJ), have been tested according to the National Institute of Justice ballistic resistance protective materials test NIJ 0108.01 Standard-Level IIIA (9 mm × 19 mm FMJ 124 g) test. Three panels, namely, a hybrid of Kevlar and glass (H–S), glass with ceramic particles (C–S), and glass with recycled rubber (R–S) have been impacted by the bullet at the center, while the fourth panel made of glass fiber (G-S) has been impacted at the side. EMI shielding properties have been measured in the X-band frequency range via the reflection-transmission method. Results indicate that four panels (K-NIJ, G-NIJ, H–S, and G-S) are capable of withstanding high-velocity impact by stopping the bullet from penetrating through the panels while maintaining their structural integrity. However, under such conditions, these panels may experience localized delamination with variable severity. The EMI measurements reveal that the highest absorptivity observed is 88% for the K-NIJ panel at 10.8 GHz, while all panels maintain an average absorptivity above 65%. All panels act as a lossy medium with a peak absorptivity at different frequencies, with K-NIJ and H–S panels demonstrating the highest absorptivity. In summary, the study results in the development of a novel, cost-effective, multifunctional glass fiber epoxy composite that combines ballistic and electromagnetic interference shielding properties. The material has been developed using a simple manufacturing method and exhibits remarkable ballistic protection that outperforms Kevlar in terms of shielding efficiency; no bullet penetration or back face signature is observed, and it also demonstrates high EMI shielding absorption. Overall, the materials developed show great promise for various applications, including the military and defense.

Coupled Thermo-Mechanical Numerical Modeling of CFRP Panel under High-Velocity Impact

Advanced composites have a brittle nature making them highly susceptible to failure and propagation under impact loading conditions. Appropriate modeling techniques to accurately simulate these conditions are required. This study presents and examines a coupled thermo-mechanical modeling technique and its associated numerical simulations for analyzing carbon fiber-reinforced composite panels subjected to high-velocity impact. The essential numerical parameters necessary to accurately simulate the selected configuration are determined through a physical-based approach, which has not been previously reported. By following the proposed framework, the conventional trial-and-error calibration process that relies on an extensive testing campaign is minimized. A stacked shell-cohesive methodology has been applied to T800/F3900 unidirectional carbon fiber/epoxy composite panel with 16 plies in a quasi-isotropic layup configuration [(0/90/45/-45)2]s. The flat composite panel was manufactured according to ASTM D8010 standards. Both failure condition and progressive damage analysis have been explored and discussed in comparison with numerical and experimental test cases available in the open literature. Thermal effects on the mechanical performance of composite targets are also discussed based on the application of the constitutive transient thermal coupling method available in LS-DYNA®. The contact heat generated by the conversion of impact-induced damage and the kinetic energy of the projectile is also evaluated and analyzed. New observations regarding modeling techniques, energy transfer, and damage mechanisms in target plates are offered. Additionally, findings related to changes in material characteristics resulting from heat transfer are discussed.

Analysis of damage localisation results in GFRP panel for different configurations of air-coupled transducers

In this paper results of the damage assessment of fiber-reinforced composite panels using guided wave propagation phenomenon are presented. For this purpose, non-contact elastic wave generation based on an air-coupled transducer (ACT) is utilised. Elastic wave sensing was based on a scanning laser Doppler vibrometer (SLDV). The problem of ACT slope angle for the effectiveness of elastic wave modes generation is analysed. It was shown that for an excitation frequency of 40 kHz it is possible to generate A0 wave mode. The authors also investigated the damage sensitivity related to panel coverage area by elastic waves with large energy. An artificial damage in the form of Teflon inserts was utilised. Moreover, the influence of single and multiple acoustic wave sources on artificial damage localisation results was investigated. For this purpose RMS wave energy maps, statistical parameters, and damage indices are utilised. Different locations of ACTs and their influence on damage localisation results are investigated. A damage imaging algorithm based on wavefield irregularity mapping (WIM) has been proposed. In this research low-cost and popular, low-frequency ACT was utilised giving the possibility of realisation of the non-contact damage localisation method.

Acoustic Emission Damage Detection during Three-Point Bend Testing of Short Glass Fiber Reinforced Composite Panels: Integrity Assessment

In this study, an acoustic emission (AE) technique was used as a passive non-destructive tool to detect the damage progress in short glass fiber-reinforced composite panels. AE detection was conducted during three-point bend tests, thus illustrating the flexural damage accumulation for composite panels with different sizes and fiber volume content. To demonstrate the universality of the employed integrity assessment methodology, AE data was detected using different timing parameters and two different transducer types, i.e., medium-band and wide-band frequency sensors. The AE waveform classification presented in this study is based on peak frequency distributions. Frequency bands that are associated with certain failure mechanisms, including matrix micro-cracking, fiber debonding, delamination, and fiber breakage, were obtained from the technical literature. Through this investigation, the concept of cumulative signal strength (CSS) and cumulative rise time versus peak amplitude ratio (CRA) as AE output parameters are shown to facilitate integrity assessment for the employed complex composite material system. Significant jumps in CSS and CRA curves could be correlated to critical strain levels and distinct damage events in the composite panels subjected to flexural loading.

Mechanical and damping property evaluation of jute fiber reinforced composite periodic core sandwich panels

ABSTRACT The present article investigates the dynamic characteristics of jute fiber-reinforced sandwich composite panels with periodic cores. The sandwich panel contains the jute fibers-reinforced polymer (JFRP) composites as face layers and the silicone rubber as the core layer. The tensile and flexural properties of JFRP composite material were examined using ASTM D3039 and ASTM D7264 standards. The finite element model was developed to obtain the dynamic properties of the composite sandwich panel with conventional and periodic cores. Furthermore, the influence of end condition, core to face layer thickness ratio, and face layer to core thickness ratio on the dynamic properties of the sandwich panels are presented. The numerical results indicate that the periodic core composite sandwich panel greatly influences the structural stiffness compared with a conventional composite sandwich panel.

Electrothermal Performance of Heaters Based on Laser-Induced Graphene on Aramid Fabric.

Nanostructured heaters based on laser-induced graphene (LIG) are promising for heat generation and temperature control in a variety of applications due to their high efficiency as well as a fast, facile, and highly scalable fabrication process. While recent studies have shown that LIG can be written on a wide range of precursors, the reports on LIG-based heaters are mainly limited to polyimide film substrates. Here, we develop and characterize nanostructured heaters by direct writing of laser-induced graphene on nonuniform and structurally porous aramid woven fabric. The synthesis and writing of graphene on aramid fabric is conducted using a 10.6 μm CO2 laser. The quality of laser-induced graphene and electrical properties of the heater fabric is tuned by controlling the lasing process parameters. Produced heaters exhibit good electrothermal efficiency with steady-state temperatures up to 170 °C when subjected to an input power density of 1.5 W cm–2. In addition, the permeable texture of LIG–aramid fabric heaters allows for easy impregnation with thermosetting resins. We demonstrate the encapsulation of fabric heaters with two different types of thermosetting resins to develop both flexible and stiff composites. A flexible heater is produced by the impregnation of LIG–aramid fabric by silicone rubber. While the flexible composite heater exhibits inferior electrothermal performance compared to neat LIG–aramid fabric, it shows consistent electrothermal performance under various electrical and mechanical loading conditions. A multifunctional fiber-reinforced composite panel with integrated de-icing functionality is also manufactured using one ply of LIG–aramid fabric heater as part of the composite layup. The results of de-icing experiments show excellent de-icing capability, where a 5 mm thick piece of ice is completely melted away within 2 min using an input power of 12.8 W.

Damage characteristics of high-performance fiber-reinforced cement composites panels subjected to projectile impact

The authors examined both experimental and numerical studies on the structural response of high-performance fiber-reinforced cement composite (HPFRCC) panels with a matrix strength of 180 MPa and a high fiber content from 1.0 to 3.0% subjected to projectile impact. The failure mechanism, such as penetration and scabbing, of HPFRCC panels was experimentally investigated according to volume fractions, the thickness of specimens, and impact velocities. The effect of fiber volume fraction and thickness on the compressive and tensile performance of HPFRCCs was also assessed through a comparison with empirical equations. In addition, a finite element model was established by using LS-DYNA to predict the impact behavior of the panels with calibration of a concrete material model based on previous experimental data. The numerical simulations of HPFRCC panels subjected to impact were verified through comparisons with the experimental results. Based on the verified FE model, a parametric study was also conducted and discussed to better understand the mechanical characteristics of HPFRCC panels under impact loading.

Spectral element formulation for damped transversely isotropic Micropolar-Cosserat layered composite panels

The present paper aims to develop governing equation of motion for in-plane dynamics of Micropolar-Cosserat composite models with damping. Constitutive model of linear elastic damping system is formulated for an anisotropic domain fiber-reinforced composite panels (FRCP); undergoing large macro as well as micro geometric deformations. The air damping and Kelvin–Voigt strain linear rate damping have been considered into the governing equations of model, while mathematical modelling and simulation of composite panel is restricted to the free-vibration and in-plane static response. The composite panel has been modeled as a Micropolar-Cosserat continuum assuming second-order micro-length of the fiber deformation; by embedding an additional equation of kinematics through the micro-rotation degree of freedom in the classical continuum model. This account for the in-plane curvature bending effects of composite panels during the loss of ellipticity of the governing equations. A transformation matrix based on Rodrigues’ rotational formula for transversely isotropic Micropolar-Cosserat lamina has been introduced; which reduces it to the well-known non-classical (classical and couple-stress) elastic formulation. The equivalent single layer (ESL) resultant stresses of FRCP in global coordinates is introduced to calculate in-plane damped and undamped response. The geometric and material linear elastic model for FRCP is derived using the spectral element method within state–space approach, and the corresponding plane-stress finite element model is validated with the undamped responses. Analytical response of damped composite panel is proposed based on available undamped simulation results.

Anisotropic water diffusion in mechanical joints of fiber-reinforced composite panels: numerical study

This paper presents numerical study on the effect of diffusion anisotropy on the accumulation of moisture in the net-tension and shear-out failure planes in fiber composite bolted connection. A composite plate containing four bolt holes was investigated. The effect of the edge distance-to-hole diameter ratios and the distance between two holes-to-hole diameter ratio was analyzed. The diffusion process was described by Fick’s law, and it was assumed that moisture is penetrating only through bolt holes in the composite joints. Technical computing software Mathematica was used to solve the 2D diffusion equation over the plate region and find the moisture concentration distribution. The numerical approach was validated against analytical expressions for diffusion in 2D plate. It was found that diffusion anisotropy ratio strongly influences the equilibrium moisture content. It was shown that depending on the joint geometry, there are significant differences in moisture content on the expected failure paths because of sorption anisotropy, which can lead to premature failure due to the increased damage done to the composite matrix, interface, interphase, and fibers.

Theoretical modeling and experimental verification of co-curing carbon fiber-reinforced polymer hat-stiffened panels with silicone airbag male mandrels

For closed-hole panels such as hat-stiffened panels, it is inevitable to use mandrels during the manufacturing process. However, the uniformity of pressure transmission of the silicone rubber mandrel with the prefabricated hole is not good, the vacuum bag mandrel is easy to be broken and wrinkled, the water-soluble mandrel is high in cost, and the invar steel metal mandrel is difficult to demold. To solve these problems, this article proposed a new method for co-curing carbon fiber-reinforced resin matrix composite hat-stiffened panels by using a silicone airbag as a mandrel through autoclaves. Firstly, the thermo-force-flow multi-field coupling finite element model of co-curing carbon fiber-reinforced polymer (CFRP) hat-stiffened panels was established by using finite element software. The co-curing process of hat-stiffened panels was simulated and studied. The influence of different thickness of silicone airbag mandrels on the wall thickness and pressure of the workpiece were found to be relatively uniform in the new process. Then, the autoclave experiment was carried out to verify the correctness of the finite element model. Lastly, the interfacial bonding strength test was carried out to verify the mechanical properties of the parts. In summary, the practicability of co-curing CFRP hat-stiffened panels with silicone airbag male mandrels was proved in this article. The precision of CFRP hat-stiffened panel was efficiently promoted by this new process.

An acoustical investigation of partial perforation in jute fiber composite panel

This study aims to develop a novel acoustic panel that constitutes more natural fiber rather than a resin matrix, and the effect of perforation depth in the composite panel is investigated. Jute fiber-reinforced composite panels undergo partial perforation using a tapping machine of depth 7.5 mm, 15 mm, and 22.5 mm to the total thickness of 30 mm. The samples are tested experimentally in an impedance tube and sound transmission loss test setup to evaluate the acoustic capabilities for the frequency range of 100–1600 Hz. For validation, the intrinsic parameters are predicted from experimental sound absorption data using the inverse characterization technique. Insight of application aspect, the panel is modeled to be present in a rectangular acoustical cavity and analyzed numerically in COMSOL Multiphysics. The impedance tube test results indicate that the peak of the sound absorption coefficient increases with increases of perforation depth. Similarly, perforation depth influences the transmission loss of the panel, and significant results noticed. The use of a jute panel in rectangular enclosure results in a 3–6 dB reduction in the overall sound pressure level of one-third octave frequencies.

Smart Adhesive Joint with High-Definition Fiber-Optic Sensing for Automotive Applications.

Structural health monitoring of fiber-reinforced composite-based joints for automotive applications during their manufacturing and on-demand assessment for its durability in working environments is critically needed. High-definition fiber-optic sensing is an effective method to measure internal strain/stress development using minimally invasive continuous sensors. The sensing fiber diameters are in the same order of magnitude when compared to reinforcement (glass, basalt, or carbon fibers) used in polymer composites. They also offer a unique ability to monitor the evolution of residual stresses after repeated thermal exposure with varying temperatures for automotive components/joints during painting using an electrophoretic painting process. In this paper, a high-definition fiber-optic sensor utilizing Rayleigh scattering is embedded within an adhesive joint between a carbon fiber-reinforced thermoset composite panel and an aluminum panel to measure spatially resolved strain development, residual strain, and thermal expansion properties during the electrophoretic paint process-simulated conditions. The strain measured by the continuous fiber-optic sensor was compared with an alternate technique using thermal digital image correlation. The fiber-optic sensor was able to identify the spatial variation of residual strains for a discontinuous carbon fiber-reinforced composite with varying local fiber orientations and resin content.

Simulation and experimental analysis of autoclave co-curing CFRP hat-stiffened panels with silicone airbag mandrels

The inflatable mandrel is easy to be broken and wrinkled during the co-curing process of the hat-stiffened wall panels. The metal mandrel is difficult to demold, the water-soluble mandrel is easy to be broken, and the pressure transmission uniformity of the silicone mandrel with preformed apertures is difficult to ensure during the manufacturing process. To solve these problems, a new process for co-curing carbon fiber-reinforced polymer hat-stiffened panels based on silicone airbag mandrel was proposed in this paper. The co-curing process of the hat-stiffened panels was simulated using finite element software and the effects of silicone airbag mandrels with different thicknesses on the thickness and pressure of the parts were studied by establishing a thermo-force-flow multi-field coupling finite element model, and found that the thickness and pressure of the parts were relatively uniform during the manufacturing process of the new method. The correctness of the finite element model was verified by the autoclave co-curing experiment. At the same time, it demonstrated the feasibility of a new process of autoclave co-curing CFRP hat-stiffened panels with silicone airbag mandrels. This new process greatly improved the accuracy of the carbon fiber-reinforced resin matrix composite hat-stiffened panels compared to conventional processes.

Multiscale Composites: Assessment of a Feasible Manufacturing Process

A very interesting field of research on advanced composite materials is the possibility to integrate new functionalities and specific improvements acting on the matrix of the composite by means of a nanocharged resin. In this way, the composite becomes a so-called “multiscale composite” in which the different phases change from nano to macro scale. For example, the incorporation of nanoscale conductive fillers with intrinsically high electrical conductivity could allow a tailoring of this property for the final material. The properties of carbon nanotubes (CNT) make them an effective candidate as fillers in polymer composite systems to obtain ultralight structural materials with advanced electrical and thermal characteristics. Nevertheless, several problems are related to the distribution in the matrix and to the processability of the systems filled with CNT. Existing liquid molding processes such as resin transfer molding (RTM) and vacuum-assisted resin transfer molding (VARTM) can be adapted to produce carbon fiber reinforced polymer (CFRP) impregnated with CNT nanofilled resins. Unfortunately, the loading of more than 0.3-0.5% of CNT can lead to high resin viscosities that are unacceptable for such kind of processes. In addition to the viscosity issues that are related to the high CNT content, a filtration effect of the nanofillers caused by the fibrous medium may also lead to inadequate final component quality. This work describes the development of an effective manufacturing process of a fiber-reinforced multiscale composite panel, with a tetra-functional epoxy matrix loaded with carbon nanotubes to increase its electrical properties and with GPOSS to increase its resistance to fire. A first approach has been attempted with a traditional liquid infusion process. As already anticipated, this technique has shown considerable difficulties related both to the low level of impregnation achieved, due to the high viscosity of the resin, and to the filtration effects of the dispersed nanocharges. To overcome these problems, an opportunely modified process based on a sort of film infusion has been proposed. This modification has given an acceptable result in terms of impregnation and morphological arrangement of CNTs in nanofilled CFRP. Finally, the developed infiltration technique has been tested for the manufacture of a carbon fiber-reinforced panel with a more complex shape.

Characterization and structural performance of hybrid fiber-reinforced composite deck panels

This paper presents the experimental and analytical investigation on the behavior of hybrid fiber-reinforced composite deck made up of glass and jute fibers embedded in vinyl ester matrix. Finite element evaluation of the flexural performance of the composite decks was carried out using ANSYS, FE software. It was observed that analytical evaluation underestimates the value of deflection of deck panels 1 and 2 by 10.91% and 18.57%, respectively, when compared to the experimental results. However, the value of strain obtained by FEA is appreciably higher than that observed during the experiment. The analytical evaluation of deck panels was further extended to HYFRP and GFRP (glass fiber-reinforced polymer) decks with varied cross sections obtained by changing the location and shape of stiffeners. The specifications stipulated by Ohio Department of Transportation (ODOT), USA, for FRP decks were used for evaluating the performance of deck panels. The values of maximum deflection and strain experienced by the deck panels with stiffeners at the web-flange joint were found to be less than that of deck panels provided with stiffeners at the center of top flange of each cellular unit. Out of the various configurations examined, the performance of decks with V-shaped stiffeners and combination of U- and V-shaped stiffeners at top and bottom web-flange joint were found to be best with substantially lower deflection and strain.