Polymer Composite Plates Research Articles

Modeling and analysis of acoustoelastic guided waves propagation in anisotropic fiber reinforced polymer composite plates under initial gradient stress

Process-induced initial gradient stress is inevitable during the fabrication of fiber reinforced polymer (FRP) composites. In this research, governing wave equations with variable coefficients are established for FRP plates under initial gradient stress, based on the acoustoelastic theories. The Legendre polynomial (LP) method is utilized to derive the solving algorithm. The dispersion curves are obtained without layer slicing, which provides a more realistic analysis model for gradient stress. The accuracy and convergence of the proposed method are discussed through numerical examples. The influences of initial gradient stress on dispersion slowness curves of Lamb and SH waves are analyzed, considering the parabolic initial gradient stress distribution, in which it’s common in the manufacturing process of FRP composites. The effect of initial gradient stress distribution on the phase velocity is investigated in detail. The influence of the anisotropic effect of FRP on guided wave propagation under initial gradient stress is discussed. The numerical analysis shows that the behavior of guided waves is influenced not only by the initial gradient stress but also dominated by propagation direction in anisotropic FRP composite plates. These results can provide a useful reference for the testing based on guided waves for FRP composite, especially when the initial gradient stress is encountered.

Dynamic properties of natural fiber-reinforced polymer composite plates and tubes

Thirty-six flax fibre-reinforced epoxy (FFRE) plates with two, three, and four fabric layers and lengths ranging from 160 mm to 270 mm and nine FFRE tubes with a diameter of 60 mm, a length of six times the tube diameter plus an overly of 50 mm with two, three, and four fabric layers were manufactured. One-hundred-eighty impulse excitation tests were conducted on FFRE plates to determine the dynamic properties of the plates in the bending mode, and 91 impulse excitation tests were conducted on the FFRE tubes to determine the dynamic properties of the tubes in the transverse, torsional, and longitudinal directions. FFRE plates showed up to six times larger specific energy capacities compared to counterpart glass fibre-reinforced polymer plates, showing significant potential for FFRE plates to replace the use of GFRP plates where considerable damping of energy is required. The results showed that the damping ratio of the FFRE plates decreased with the increase in layers and natural frequency. For the FFRE tubes, the highest damping ratio belonged to the transverse vibration mode, followed by the torsional or longitudinal vibration modes.

Experimental investigation of the performances of thick CFRP, GFRP, and KFRP composite plates under ballistic impact

Abstract This study discusses the experimental results of the ballistic impact on thick-layered carbon fibre-reinforced polymer (CFRP), glass-based FRP (GFRP), and Kevlar-based FRP (KFRP) composite plates. Ten 10 mm plates of each type were manufactured via the hand lay-up and vacuum bagging techniques to produce plates with a thickness of 2 mm each, which were bonded together using epoxy adhesive and hot pressed at 75°C to obtain thick layered plates with a total thickness of 20 mm each. The specimen plates were tested according to the NIJ 0108.01 standard in a special firing room using a 9 mm G2 Elite handgun with a full metal jacketed round nose 9 mm × 19 mm Mu1-TJ bullets moving at a velocity of approximately 358 m/s. The results indicated that no total penetration occurred on any of the plates. The bullets were destroyed by impact, and the penetration depths of the CFRP, GFRP, and KFRP plates were 11.10, 9.95, and 22.22%, respectively. The layered structures in these plates appear to have changed the penetration behaviour compared with previous studies. In this study, delamination was the primary failure mode.

Active vibration control of piezoelectric multilayers FG‐CNTRC and FG‐GPLRC plates

AbstractThis study investigates the active vibration control of multilayer Functionally Graded Carbon NanoTube Reinforced polymer Composite (FG‐CNTRC) plates and multilayer functionally graded graphene platelets reinforced polymer composite (FG‐GPLRC) plates covered with a piezoelectric layer (PZTG1195N) serve as both actuators and sensors. The plate's heart is supposed to be reinforced nonlinearly using both types of reinforcement. Active vibration control of plates under uniform load was achieved by utilizing a velocity feedback control algorithm with a specific gain value. The finite element method is employed to analyze both the static and dynamic behavior of a square plate discretized into 9‐node quadratic finite elements with 5 ° of freedom per node. The material properties are assumed to change across the thickness direction following a power law distribution, exhibiting various patterns: Uniform Distribution (UD), as well as Functionally Graded types X, O, and A (FG‐X, FG‐O, and FG‐A). The geometrical nonlinear equations are solved by the Newmark integration method. This work begins by validating the natural frequencies of a Functionally Graded (FG) composite plate reinforced with four different distributions of Nano‐filler and then aims to show the effect of the nonlinear distribution of nanofillers on the plate's stiffness. The Results obtained after the execution of a developed code highlight the significance of employing a nonlinear distribution of nanofillers to attenuate vibrations.Highlights FG composite and sandwich plates reinforced with GPLs and CNTs. Effect of nonlinear nanofillers distribution of reinforcement on free and forced vibration. The ability of the nonlinear distribution of nanofillers to attenuate forced vibrations.

Detection of Barely Visible Impact Damage in Composite Structures Using Backward Sweep Vibro-thermography Technique Utilizing Asymmetry in Local Defect Resonance

ABSTRACT In this article, local defect resonance-based vibrothermography has been studied for different sweep direction and ranges. Two different carbon fiber-reinforced polymer (CFRP) composite plate has been fabricated from vacuum assisted resin transfer molding. In the first plate, a flat bottom hole has been made and two barely visible impact damages are created in other plate. The area of delamination has been determined from phased array ultrasound testing. Laser doppler vibrometry (LDV) has been performed first for different sweep ranges and directions. The CFRP plate is excited with a piezoelectric element at 150 Vpp and the vibration over defect area is captured using a single point laser doppler vibrometer, operating in scanning mode. It has been found that vibration amplitude at local defect resonance (LDR) frequency increases in narrow sweep range compared to a wideband excitation. Again, in both cases, it has been found that backward sweep produces more amplitude compared to forward one due to softening nonlinearity. An asymmetry in LDR frequency is also been observed when the sweep range is further narrowed. An uncooled microbolometer camera is used for reception in case of vibrothermography. Backward sweep is found to be more effective as compared to the forward one and the temperature increment increases in case of narrowband excitation range.

Structural performance evaluation of hybrid polymer composites for critical infrastructure pick-and-place robot grippers using silica nanoparticles

PurposeThis study focuses on the structural performance assessment of hybrid polymer composites for pick-and-place robot grippers used in critical infrastructure. This research involved the creation of composite materials with different nanoparticle concentrations, followed by extensive testing to assess the mechanical properties of the materials, such as strength, stiffness and durability.Design/methodology/approachThe composites comprised bidirectional interply inclined carbon fibers (C), S-glass fibers (SG), E-glass (EG), an epoxy matrix and silica nanoparticles (SNiPs). During construction, the composite materials must be carefully layered using quasi-static sequence techniques (45°C1/45°SG2/45°EG2/45°C1/45°EG2/45°SG2/45°C1) to obtain the epoxy matrix reinforcement and bonding using 0, 2, 4 and 6 wt. % of silica nanoparticles.FindingsAccording to various test findings, the 4 wt. % of SNiPs added to polymer plates exhibits the maximum strength outcomes. The average results of the tensile and flexural tests for the polymer composite plates with 4 wt. % addition SNiPs were 127.103 MPa and 223.145 MPa, respectively. The average results of the tensile and flexural tests for the plates with 0 wt.% SNiPs were 115.457 MPa and 207.316 MPa, respectively.Originality/valueThe authors hereby attest that the research paper they have submitted is the result of their own independent and unique labor. All of the sources from which the thoughts and passages were derived have been properly credited. The work has not been submitted for publication anywhere and is devoid of any instances of plagiarism.Highlights The study enhances the engineering materials for innovative applications.The study explores the mechanical behavior of carbon/S-glass/E-glass fiber composites.Silica nanoparticles were enhancing mechanical characteristics of the composite structure.

Delamination imaging in composites using cross-correlation method by non-contact air-coupled Lamb waves

This paper presents a cross-correlation damage detection technique using damage scattered waves of all directions cross-correlate with the incident waves for delamination imaging in carbon fiber reinforced polymer (CFRP) composite plate. The presented imaging can not only detect the delamination but also precisely quantify the damage with locations and sizes. First, a CFRP composite sample with interlaminar delamination by inserting the Teflon layer is designed and manufactured in house using the hot-press machine. And a three-dimensional model of composite sample is simulated using the finite element method. Next, the cross-correlation imaging algorithm is introduced in detail, and the cross-correlation imaging proof-of-concept study is conducted with the simulated Lamb waves in the composite sample. Finally, a fully non-contact air-coupled transducer and scanning laser Doppler vibrometer system with a single-mode Lamb wave method is established to actuate and sense the interrogating Lamb waves in the structure. The imaging method is experimentally implemented for the one delamination and two delaminations imaging and quantification.

Buckling, bending and dynamic analyses of laminated three-phase polymer/graphene/carbon fiber composite rectangular plates

The bending and dynamic buckling analysis of graphene reinforced with carbon fiber reinforced polymer (CFRP) composite plates was investigated in this study. The CFRP composites were fabricated using the hand layup method. The mechanical characteristics of CFRP composites with 0–1 wt% graphene reinforcement were evaluated using ASTM tests. The experimental dynamic analysis is carried out on graphene reinforced CFRP composites. A higher order finite element (FE) formulation is implemented to compute the characteristics of the CFRP plate using MATLAB software. The FE model's validity is compared to numerical data reported in the literature, and the results demonstrate excellent agreement. Furthermore, parametric analysis is performed to explore the influence of wt.% of graphene, aspect ratios, and end conditions on the bending and dynamic buckling properties of graphene reinforced with CFRP composite plates.

Reversible and irreversible effects on the epoxy GFRP fiber-matrix interphase due to hydrothermal aging

Epoxy R-Glass Fiber-Reinforced Polymer (GFRP) composite plates were hydrothermally aged at 60 °C for 23, 75, and 133 days. The water content reached 0.97 wt%, 1.45 wt% and 1.63 wt%, respectively. The studied GFRP matrix was inert to hydrolysis or chain scission, allowing for investigation of irreversible changes in the fiber-matrix interphase due to hydrothermal aging upon re-drying. During each period, a subset of the specimens was removed from the water bath and dried in a chamber. The weight loss upon drying was explained with epoxy leaching (impurities), sizing-rich interphase hydrolysis, glass fiber surface hydrolysis, accumulated degradation products escaping, and water changing state from bound to free. The influence of hydrothermal aging on the fiber-matrix interfacial properties was investigated. Lower interfacial strength of hydrothermally aged (wet) samples was attributed to plasticization of the epoxy, plasticization and degradation of the sizing-rich interphase (including formation of hydrolytic flaws), and hydrolytic degradation of the glass fiber surface. The kinetics of epoxy-compatible epoxysilane W2020 sizing-rich interphase hydrolysis provided an estimate of ca. 1.49%, 4.80%, and 8.49% of the total composite interphase degraded after 23, 75, and 133 days, respectively. At these conditions, the interface lost 39%, 48%, and 51% of its strength. Upon re-drying the specimens, a significant part of the interfacial strength was regained. Furthermore, an upward trend was observed, being 13%, 10% and 3% strength, respectively; thus, indicating a possibility of partial recovery of properties.

Thermally conductive polypropylene composites as corrosion‐resistant materials for plate heat exchangers

AbstractThe suitability of polypropylene‐graphite composites as materials for corrugated heat exchanger plates is investigated, as the associated materials have low density (<2.3 g/cm3) and excellent corrosion resistance at a comparatively low price. Therefore, custom‐made polymer composite plates with a thickness of 1–2 mm and a filling degree of up to 80 wt% were evaluated for their thermal and mechanical suitability with regard to their use in plate heat exchangers. Three‐point flexural tests show that the loading of polypropylene with graphite leads to mechanical properties that are suitable for the application of heat exchanger plates. The simulated maximum overpressure is greater than 7 bar. The thermal conductivity of the composites was increased by a factor of 20 compared to pure polypropylene, resulting in thermal conductivities of up to 2.74 W/mK. Considering the density differences between the developed composites and stainless steel, similar thermal performances over a wide range of process conditions are obtained. Moreover, the composites investigated have lower crystallization fouling susceptibility compared to stainless steel, which is attributed to the low surface free energies of approximately 25 mN/m. For calcium sulfate fouling, the fouling resistance on stainless steel exceeds that on the composite by 1.5 m2K/kW after 60 h.

Low-velocity impact responses of composite structures incorporating shear thickening fluid tubes under various temperatures

This study proposes a novel approach to enhance the impact resistance of carbon fiber reinforced polymer (CFRP) composite plates by incorporating an additional layer consisting of shear thickening fluid (STF)-filled tubes, resulting in a hybrid composite referred to as STF hybrid composite (STFC). The proposed STFC plates were subjected to low-velocity impact tests under varying impact energies and temperatures to consider realistic operating conditions for practical applications. It was found that the insertion of STF-filled tubes into the composite structure led to lower contact forces during impact and reduced residual velocities of the impact striker at temperatures ranging from 25 to 100 °C, thereby improving the impact resistance of the structure. Specifically, the STFC plates exhibited enhanced energy absorption capabilities, with energy absorption increasing by up to 38.10% at 25 °C under the impact energy of 2 J, potentially mitigating secondary damages within the composite structure. These results suggest that the proposed STFC hybrid composite is a promising solution for applications requiring high energy absorption capabilities.

Experimental study on the mechanical properties of CFRP/epoxy composite plates under seawater immersion

This study investigates the effects of seawater immersion at different temperatures on the degradation and viscoelastic behavior of carbon fiber-reinforced polymer (CFRP) composite plates. The present study investigated the effects of seawater immersion on the degradation of mechanical properties at 20 °C, 40 °C, and 60 °C of the carbon fiber reinforced polymer (CFRP) composite plates. The specimens were prepared by hand lay-up and cured under water for 7 days before immersion in artificial seawater for 6 months. Interlaminar shear strength (ILSS), tensile strength, and dynamic mechanical analysis (DMA) tests were performed periodically over a six-month exposure period, and scanning electron microscopy (SEM) was used to characterize aging damage and fracture morphology. The long-term shear behaviour of CFRP plates in seawater has been predicted using the Arrhenius theory. The results show that immersion in seawater significantly reduces ILSS, especially at higher temperatures and longer immersion times. However, the overall tensile properties of CFRP plates were not significantly affected. Dynamic mechanical analysis (DMA) revealed a decrease in the damping (tan δ), indicating a reduction of the fiber-matrix adhesion. The long-term life prediction showed that CFRP plates subjected to seawater immersion are susceptible to degradation, with a stable retention of interlaminar shear strength at 70% for the composite laminate.

Effect of volume ratio and hybrid mode on low-velocity impact properties of unidirectional flax/carbon fiber hybrid reinforced polymer composites

Hybrid fiber reinforced polymer composites have attracted widespread attention because they can fully utilize the advantages of two different types of fibers. To produce fiber reinforced polymer composites with excellent impact properties, unidirectional carbon/flax hybrid fiber reinforced polymer composite (HFRP) plates were developed using a filament-winding technique. The effects of the carbon fiber content and hybrid mode (a carbon–flax–carbon or flax–carbon–flax structure) on the impact properties and residual compressive properties of the HFRP plates were studied. Acoustic emission tests were performed to characterize the damage during impact, and the K-means cluster analysis method was used to investigate the HFRP damage development during post-impact compression. The test results indicate the higher carbon fiber contents enhanced their specific energy absorption (SEA), as the impact-induced brittle fracturing of the carbon-fiber layers was more severe. The hybrid mode and impact energy level critically influenced the HFRP SEA behavior. The HFRP plate with flax skin exhibited high SEA at a low impact energy, whereas that with carbon fiber skin exhibited high SEA at a high impact energy along with perforation. A more severe extension of the damage caused by the original impact occurs in the impacted HFRP under a compressive load.

Debonding detection in FRP-strengthened concrete structures utilising nonlinear Rayleigh wave mixing

This paper reports an investigation on the use of Rayleigh wave mixing method for the debonding detection in concrete structures strengthened with externally bonded fibre-reinforced polymer (FRP) composite plates. A three-dimensional (3D) finite element model is developed to simulate the propagation of Rayleigh waves in FRP-strengthened concrete structures. In this model, the frequency domain of the transmitted waves shows the generation of second harmonics and combinational harmonics on account of debonding. The numerically simulated results are then experimentally validated with carbon fibre-reinforced polymer (CFRP)-plated concrete blocks containing two different sizes of debonding. Based on the experimentally verified numerical model, parametric studies are then conducted, where a nonlinear debonding crack growth parameter is proposed. The nonlinear Rayleigh wave mixing method is proven to be practical, reliable, and sensitive for detecting debonding at bonded concrete-FRP interfaces in FRP-strengthened reinforced concrete (RC) structures.

Resonant air coupled inspection of glass fiber reinforced polymer composite plate using single sided access of near and far side of low velocity impact damage

Resonance based nonlinear techniques works efficiently in detecting small size damages in the composite structures. Local defect resonance (LDR) is a resonance based nonlinear technique which enables to activate the damage directly. In this study, recently developed LDR based automated methodology is carried out from far side of the impact damage to detect the LDR frequency and mode shape of the impact damage. This methodology is implemented by carrying out experiments on glass fibre reinforced polymer (GFRP) plate using air coupled emission (ACE) technique. This plate contains three artificial delaminations and one low velocity impact damage. Initially, the LDR frequency and mode shape of each damage is accomplished using ACE testing, justified with Laser Doppler Vibrometry (LDV). Later, the Otsu’s algorithm is performed to get the accurate size of the impact damage. Subsequently, a broadband backward sweep is used to detect all delamination including the impact damage. Then, maximum amplitude of each frame has been found from output data of all spatial nodes. Later, the LDR frequency frame ( N L) has been identified in the time domain from the slope and curvature plots followed by Discrete Fourier Transform (DFT) to detect the LDR frequency and mode shape of the damage. So, it has been observed that less than defect size is obtained when inspected from the far side. Further, this method will be extended to find out the depth of individual damage.

INVESTIGATION OF DRILLING PERFORMANCE OF REINFORCED POLYAMIDE 6 POLYMER COMPOSITE

Polyamides are preferred polymer materials for manufacturing industrial products due to their lightness, resistance to corrosion, ease of processing, and recyclability. In this study, the machinability properties of Polyamide 6 (PA6) polymer composite plates reinforced with chopped carbon fiber (CF) and multi-walled carbon nanotube (MWCNT) in different proportions were investigated by the drilling method using different cutting tools and cutting parameters. The experiments were carried out according to the L16 orthogonal array. Drilling experiments were carried out in a dry environment. The deformations occurring on the inlet and outlet surfaces of the drilled samples were calculated, and the surface roughness (Ra) of the hole walls was measured. According to the results obtained, the particle addition made to the PA6 polymer reduced the Ra. It has been observed that high cutting speed and low feed rate are ideal parameters to achieve low Ra and low inlet-outlet deformations.

Comparative study on the low-velocity impact properties of unidirectional flax and carbon fiber reinforced epoxy plates

Flax and carbon fibers reinforced polymer composites have high potentials to be used as sustainable building materials. To understand the impact resistance of these fiber composites, the present article studied the impact resistance of unidirectional flax fiber and carbon fiber reinforced polymer (FFRP and CFRP) composite plates. The impact response, damage resistance, and impact tolerance were investigated using drop hammer impact and compression after impact (CAI) tests. The internal damage of FFRP and CFRP due to impact loads was studied using acoustic emission technology. In addition, the development process of impact damage was analyzed. CFRP plates show a higher specific energy absorption rate than that of FFRP, because of the more serious internal damage and brittle fracture tendencies. Matrix cracking was the primary damage in FFRP and CFRP under impact load. Compared with CFRP, FFRP possesses a higher CAI due to less damage. Further expansion of the matrix crack caused by the original impact occurs in the impacted fiber-reinforced polymer composites (FRP) under a compressive load.

APPLICATION OF HOOKE’S LAW TO ANGLE PLY LAMINA

Aerospace-grade carbon fiber reinforced polymer composite plates with four different fiber orientations 0º, 30º, 45ºand 60º is produced with the autoclave curing method and subjected to tensile testing. The stress-strain curves of the composite specimens are compared with Hooke’s law. It is observed that Hooke’s law coincides precisely with the experimental results for samples containing fibers parallel to the loading direction. However, it does not coincide with samples where the fibers make a certain angle with the applied load direction.. Moreover, it is reported that Hooke’s law converges the experimental results for small strain values but diverges significantly from the experimental results at higher strain values.

Free vibration analysis and prediction modeling of delaminated tapered FRP composite plates

Delamination (the separation between plies) is a common failure in Fiber Reinforced Polymer (FRP) laminated composites. The presence of delamination reduces the structural stiffness and changes in dynamic responses. The change in dynamic parameters can be successfully used for assessing structural health monitoring (SHM) for composite structures. SHM requires large amount of numerical/experimental data. This study focuses on the influence of the delamination parameters (size and in-plane location) on vibration behavior of a laminated tapered fiber reinforced polymer (FRP) composite plate with ply drop-off. Furthermore, developing a surrogate model as a fast-executing model to predict the shift in the natural frequency to reduce the computational effort for solving forward problems. The layerwise theory (LWT) has been used, and the delamination is modeled by “constrained mode” were solved using the finite element method (FEM). The numerical model was validated with an experimental modal analysis of tapered plates without delamination to make the model more robust. The effect of delamination was studied using surface plots produced using response surface methodology (RSM). The results show that the delamination size and location significantly affect the natural frequency shift. The RSM and ANN models were considered as surrogate models, and it was evaluated using an experimental modal analysis. The results shows that the single-output ANN model can predict the shift in the natural frequency with a minimum Root Mean Square Error (RMSE).

Enabling self-shape estimation of composite structures using distributed microfabricated strain gauge networks

In this study, smart multifunctional composites (SMC) were developed to enable state estimation of structures in terms of the deformations at distributed locations due to applied loads and temperature gradients. The SMC was composed of a carbon fiber-reinforced polymer (CFRP) composite plate and an embedded microfabricated sensor network of densely distributed strain gauges. The microfabricated sensor network, with serpentine signal wires connecting the sensing elements, was manufactured on a 100 mm diameter silicon wafer using integrated circuit batch processing techniques. The robustness of the SMC was investigated and verified through shape estimation under mechanical loads and temperature gradients applied to the SMC. The mechanical load was applied to the SMC with fixed boundaries on four edges. The temperature gradient was applied to the SMC with simple supports on the four corners of the SMC plate by applying a uniform temperature on one side while controlling the temperature of the other side close to the room temperature. The results show that the SMC provides the shape of the deformed structure under loads with high resolution. Moreover, a numerical analysis of the SMC implemented in ABAQUS demonstrates a close correlation between the estimated deformed shape and the simulated structure allowing the potential establishment of a digital twin. The SMC can be customized based on different requirements and applications by selecting the type, number, and locations of the sensors. The shape and state of the structure obtained from the SMC during operation can be used for online control, autonomy, decision-making, and maintenance.