Polymer Composite Plates Research Articles

Guided wave excitation and propagation in damped composite plates

Guided wave attenuation in composites due to material damping is strong, anisotropic, and cannot be neglected. Material damping is a critical parameter in selection of a particular wave mode for long-range structural health monitoring in composites. In this article, a semi-analytical finite element approach is presented to model guided wave excitation and propagation in damped composite plates. The theoretical framework is formulated using finite element method to describe the material behavior in the thickness direction while assuming analytical expressions in the wave propagation direction along the plate. In the proposed method, the Kelvin–Voigt damping model using a complex frequency-dependent stiffness matrix is utilized to account for anisotropic damping effects of composites. Thus, the existing semi-analytical finite element approach is being extended to include material damping effect. Theoretical predictions are experimentally validated using scanning laser Doppler vibrometer measurements of guided wave propagation generated by a circular piezoelectric wafer active sensor transducer in a unidirectional carbon fiber reinforced polymer composite plate. The proposed method achieves good agreement with the experimental results.

Numerical simulation of FRP-strengthened RC slabs anchored with FRP anchors

Reinforced concrete (RC) members such as beams and slabs can be strengthened in flexure by bonding fibre-reinforced polymer (FRP) composite plates to their tension face. Experimental studies have shown that anchorage of the FRP plates with anchors made from FRP (i.e. FRP anchors) can delay and even eliminate premature debonding failure. This paper reports on the finite element (FE) analysis of a series of FRP-strengthened RC test slabs anchored with FRP anchors. Prior to introducing the FE modelling strategy, a semi-empirical load-slip model is proposed for modelling the FRP anchors. The load-slip model, which is calibrated from FRP-to-concrete joint tests, is novel and is also essential for the analysis of the slabs. The numerically simulated results of load, deflection and strain for the test slabs are shown to be in good agreement with test measurements. The results help provide needed insight to the influence of FRP anchors upon FRP-strengthened members.

Use of fiber Bragg grating sensors for monitoring delamination damage propagation in glass-fiber reinforced composite structures

Embedded fiber Bragg grating (FBG) sensors have been widely used for damage monitoring of fiber composite structures for a few decades. However, many remaining engineering challenges have delayed FBG based in situ structural health monitoring (SHM) systems. One of the major problem associated with FBG based SHM system is the unavailability of reliable data processing algorithms. The present work details a study which has been undertaken for identification of delamination crack propagation in fiber reinforced polymer (FRP) composite plate under uniaxial loading. The strain measured by embedded FBG sensors closer to the crack tip was used to qualitatively and quantitatively analyse delamination damage propagation using recently proposed elasto-plastic model. Strain energy release rate was calculated and compared with the model prediction. The study has concluded that the delamination crack propagation in a FRP composite can be monitored successfully using an integral approach of FBG sensors measurements and the predictions of proposed elasto-plastic model.

An analytical study on buckling behavior of CNT/polymer composite plates using first order shear deformation theory

Most plates used in engineering structures such as aircraft wings, ship ducts and buildings, although quite capable of resisting tensile loads, are poor in withstanding compression. In order to avoid premature failure under compression, it is important to know buckling behavior of the plate. This article primarily deals with the analytical study of buckling behavior of a carbon nanotube reinforcing polymer composite plates based on the first order shear deformation theory by employing Mori-Tanaka micromechanics approach to obtain elastic properties. In this investigation, an attempt is made for evaluating the effect of plate thickness, CNT volume fraction, stacking sequence and CNT radii on the buckling of plates.

Analysis of Uncertainty in Digital Image Correlation Technique for Strain Measurement

Digital Image Correlation is a full-field deformation measurement technology which is based on images. The surface of specimen is covered with a random speckle pattern. The speckle pattern deforms together with the testing surface and carries deformation information. Therefore its distribution clearly influences the measurement accuracy. This paper presents an investigation of quality of speckle pattern and uncertainties involved in strain measurements. Two different speckle patterns are created on a carbon fiber reinforced polymer composite plate specimen. DIC results are compared with finite element analysis results. The speckle pattern quality is characterized to study its influence on the measurement accuracy.

Experimental Investigation and Analysis of a Mechanical and Thermal Properties of Hybrid Polymer Composite Plates

Experimental Investigation and Analysis of a Mechanical and Thermal Properties of Hybrid Polymer Composite Plates

Nondestructive evaluation of GFRP composite including multi-delamination using THz spectroscopy and imaging

We utilize a fiber-coupled terahertz time-domain spectroscopy system (THz-TDS) based on photoconductive antennas to visualize multi-delamination and their thickness in a glass-fiber-reinforced polymer (GFRP) composite plate. We simulate a hidden multi-delamination by inserting a Teflon film in the GFRP composite plate that is fabricated using the vacuum-assisted resin transfer molding (VARTM) process. Reflected or transmitted terahertz (THz) waves are recorded from GFRP samples mounted on the x–y linear motorized stage during the investigation. The x–y linear motorized stage is driven in steps of 0.2 mm, thereby allowing us to scan the sample. We examine and compare the performances of the THz time-domain visualization (TTV) and THz frequency-domain visualization (TFV) algorithms to evaluate their characteristics for the visualization of defects. The thickness of the GFRP sample and multi-delamination is estimated using the reflection geometry method. Finally, we confirm that the hidden multi-delamination of the GFRP sample has been successfully visualized in the B- and C-scans. In addition, the thicknesses of the GFRP sample and the simulated delamination as compared with the experimental values exhibit a close consistency.

Three-dimensional woven carbon fibre polymer composite beams and plates under ballistic impact

Clamped rectangular orthogonal 3D woven carbon composite beams under ballistic impact at a velocity range 60ms-1⩽v0⩽190ms-1 were investigated in order to understand the damage mechanisms within the material and the role of through-the-thickness (TTT) reinforcement. Experimental tests revealed three distinct categories of beam response: (i) low velocity impacts (v0<110ms-1) which featured projectile rebound, with dominant matrix cracking and localised fibre fracture, (ii) medium velocity impact (110ms-1⩽v0<148ms-1) which exhibited a stretch-deformation dominated failure mechanism, and (iii) higher velocity impacts (v0⩾148ms-1) which resulted in projectile penetration, combined with longitudinal fibre fracture at the centre of the sample. Finite element (FE) simulations were conducted to understand the experimental outcomes, which showed sufficient fidelity and captured the three distinct beam response regimes. The presence of the TTT-reinforcement can suppress the inter-laminar matrix crack propagation and increase the material ballistic impact resistance for low velocity impact and high velocity impact. However, for medium velocity impact, the in-plane fibre fracture surface was found to be at the locations of TTT-reinforcement. This may suggest that the TTT-reinforcement creates weak points for the stretch-deformation dominated failure mechanism. The verified FE simulations were conducted to predict the multi-hit ballistic impact limit surfaces for the clamped circular 3D woven composite plates, and for the equivalent laminate composite without the presence of the TTT reinforcement. The numerical results suggested the presence of TTT reinforcement could improve the multi-hit ballistic resistance of the composite plates for multi-hit scenarios where the initial impact is 50%–95% of the ballistic limit of the plates.

Bending and buckling analyses of functionally graded polymer composite plates reinforced with graphene nanoplatelets

Abstract This paper presents static bending and compressive buckling analyses of functionally graded multilayer graphene nanoplatelet (GPL)/polymer composite plates within the framework of the first-order shear deformation theory. The GPL weight fraction shows a layer-wise change along the thickness direction with GPLs uniformly dispersed in the polymer matrix in each individual layer. The effective Young's modulus of the nanocomposites is estimated through the Halpin-Tsai micromechanics model while the effective Poisson's ratio is determined by the rule of mixture. Analytical solutions are obtained for the static deflection and critical buckling load of the simply supported functionally graded GPL/polymer plates by using the Navier solution technique. Numerical results show that GPL distribution pattern, weight fraction, and geometry and size have significant influences on the bending and buckling behaviors of the functionally graded GPL reinforced nanocomposite plate.

The effect of compression molding parameters on the electrical and physical properties of polymer composite bipolar plates

The performance of polymer electrolyte membrane fuel cell (PEMFC) greatly depends on the properties of the components. Bipolar plate is one of the key components of PEMFC and the properties of the plates on fuel cell performance are critical. Electrical conductivity and surface roughness of the bipolar plate appear very important properties to minimize ohmic resistance and optimize water management, respectively. The composite bipolar plates having conductive fillers and thermosetting resin binder are produced by compression molding. Response Surface Methodology (RSM) has been applied to optimize the production conditions of bipolar plate. Electrical conductivity, physical appearance and roughness are chosen as response parameters and molding temperature, pressure and time are chosen as independent parameters. The main challenges of this study are observation of the individual and combined effects of these parameters on bipolar plate properties by RSM. The optimization of the production conditions of polymer composite plate is carried out by aiming maximum electrical conductivity and minimum time. The maximum electrical conductivity of 107.4 Scm−1 is obtained at temperature of 187 °C, pressure of 119 bar and time of 5 min. It is found that the polymer composite plates produced by the compression molding process at minimum time satisfied the electrical conductivity target of Department of Energy (DoE).

Large deflection geometrically nonlinear analysis of functionally graded multilayer graphene platelet-reinforced polymer composite rectangular plates

A large deflection geometrically nonlinear analysis of functionally graded (FG) multilayer graphene platelet-reinforced polymer composite (GPL-RPC) rectangular plates subjected to uniform and sinusoidal transverse mechanical loadings is performed in this article. Based on the sinusoidal shear deformation plate theory and von Kármán nonlinear strain-displacement relations, the nonlinear governing equilibrium equations and boundary conditions are developed by using the principle of virtual work. It is assumed that the weight fraction of GPL nanofillers layer-wisely changes across the thickness of plate. The effective Young’s modulus of FG-GPL-RPCs is approximately calculated via the modified Halpin-Tsai model. Also, the effective Poisson’s ratio and mass density are determined by employing the rule of mixture. The investigation is performed by using a numerical solution approach. To evaluate the nonlinear bending stiffness of FG multilayer GPL-RPC plate, the discretization of governing equations and boundary conditions is carried out using the generalized differential quadrature (GDQ) method, and the pseudo arc-length continuation technique is employed to solve the set of nonlinear algebraic discretized equations to obtain the load-deflection curve. Numerical problems are given to reveal the influences of GPL distribution pattern, weight fraction, geometry of GPL nanofillers, length-to-thickness and edge conditions on nonlinear bending responses of the GPL-RPC plates.

Buckling and Free Vibration of Nonuniformly Heated Functionally Graded Carbon Nanotube Reinforced Polymer Composite Plate

Buckling and free vibration behavior of functionally graded carbon nanotube reinforced polymer composite plate subjected to nonuniform temperature fields have been investigated using finite element approach. The effective material constants of the plate are obtained using the extended rule of mixture along with efficiency parameters of the carbon nanotube (to include geometry-dependent material properties). Influence of boundary conditions, aspect ratio, functional grading of the carbon nanotube, nonuniform thermal loading on thermal buckling and free vibration behavior of the heated plate are analyzed. It is observed that temperature fields and functional grading are influenced on the critical buckling temperature of the plates. Further, nature of functional grading showed significant change in buckling mode shapes irrespective of the boundary conditions. The first few natural frequencies of the plate under thermal load decreases as the temperature increases and they are influenced significantly by the nature of temperature field. Variations in free vibration mode shapes of the square plates found with not significant change as temperature increases. However, free vibration modes of the rectangular plates are sensitive to the nature of temperature field whenever there is a free edge associated with the boundary condition. Influence of functional grading on the free vibration mode shapes is not significant in contrast with the free vibration natural frequencies. The magnitude of free vibration natural frequencies of functional grade-X type carbon nanotube reinforcement showed higher in comparison with other two types of reinforcements considered here.

Buckling and postbuckling of biaxially compressed functionally graded multilayer graphene nanoplatelet-reinforced polymer composite plates

The present paper investigates the biaxially compressed buckling and postbuckling behaviors of functionally graded multilayer composite plates reinforced with a low content of graphene nanoplatelets (GPLs) that are randomly oriented and uniformly dispersed in the polymer matrix within each individual layer. The material properties of the GPL-reinforced composite (GPLRC), which are graded along the thickness direction due to a layer-wise change in GPL weight fraction, are evaluated through a micromechanics model. Theoretical formulations are based on the first-order shear deformation plate theory and von Kármán-type nonlinear kinematics and include the effect of an initial geometric imperfection. A two step perturbation technique is employed to determine the asymptotic postbuckling solutions and the biaxial compressive postbuckling equilibrium paths of both perfect and imperfect plates simply supported on all edges. The effects of GPL weight fraction, distribution pattern, geometry and size as well as total number of layers on the buckling and postbuckling behaviors of functionally graded GPLRC plates are examined in detail.

Vibration, buckling and bending behavior of functionally graded multi-walled carbon nanotube reinforced polymer composite plates using the layer-wise formulation

Polymer matrix nanocomposites reinforced with uniformly dispersed and randomly oriented multi-walled carbon nanotubes (MWCNTs) are identified as excellent candidates for functionally graded structural members. This paper presents static and dynamic behavior of functionally graded polymer composite plates reinforced by randomly oriented multi-walled carbon nanotubes using novel layer-wise formulation concept. The weight fraction of MWCNTs in functional graded plate is represented by layer-wise variation along the thickness and MWCNTs are considered as uniformly dispersed in each layer. The effective elastic modulus of nanocomposite plate is predicted with modified Halpin-Tsai model, while the Poisson’s ratio and density are determined by rule of mixtures. System of governing equations are derived based on generalized higher order shear deformation (HSDT) plate theory and Navier technique is employed to obtain the solution for free-vibration, buckling and static bending problems of simply supported plates under axial and transverse loading conditions at various aspect-ratios. In order to understand the effect of important reinforcement and plate parameters on the natural frequencies, critical buckling loads and bending deflections, different parametric studies are conducted. Results reveal that different types of weight distributions have significant influence on structural characteristics.

Carbon fiber-reinforced polymer composite drilling via aluminum chromium nitride-coated tools: Hole quality and tool wear assessment

Drilling into carbon fiber-reinforced polymer composites presents a stiff challenge in terms of ensuring hole quality aspects such as delamination, roughness, roundness, etc. while maintaining an adequate tool life. The hardened carbon fibers in laid up form generally give rise to chips in powdered form that contribute significantly to tool wear problem. To overcome the aforementioned issues, the use of high performance tools has been reported. This paper reports on the usage of yet another novel high performing but much economical aluminum chromium nitride-coated tools that are typically employed for metallic parts. The effect of aluminum chromium nitride tools at three spindle speeds with constant feed rate was evaluated on hole quality, tool wear, and chip formation pattern of carbon fiber-reinforced polymer composite plates. The results were compared with the performance of conventional high speed steel tools taken as baseline. It was found that the coated tools help significantly improve hole quality and provide appreciable tool life at specific machining parameters.

Flexural Performance of RC Beams Strengthened with Polyester FRP Composites

In this study, cost-effective polyester fiber reinforced polymer (PFRP) composite plates were used as external strengthening materials of conventional reinforced concrete (RC) beams. The flexural behavior of PFRP strengthened RC beams was investigated. Two RC control beams and six PFRP strengthened RC beams were constructed and tested under four-point bending. The dimension of these concrete beams used was 150 mm × 300 mm × 2000 mm. The experimental variables included thickness of PFRP (four and six layers of laminates) plates and steel reinforcement ratio (0.223 and 0.503%). The test results indicated that compared with the control beams, the strengthened beams experienced significant enhancement in ductility, ultimate load and deflection due to the PFRP reinforcement. The increase in transverse load due to PFRP strengthening was more pronounced for the RC beam with a low steel reinforcement ratio (0.223%). The ductility (calculated from both displacement-based and energy-based approach) of the PFRP strengthened RC beam with the low steel ratio was larger than that of the strengthened beams with the large steel ratio. The experimental ultimate loads of the PFRP strengthened beams were also compared with the predictions based on the equation given in ACI 440.2R-08 proposed for RC beams strengthened by synthetic glass or carbon FRP materials. This study, therefore, implied that the PFRP has potential as external strengthening materials of concrete structures.

Mechanical and morphological study of polymer composite plates having different fiber surface treatments with particular response to high velocity projectile impact

This study investigates morphological and mechanical behaviors of polymer composite plates reinforced with surface modified glass fiber woven roving with special interest in high velocity impact response. Four types of surface modification were applied to the glass fiber surface, namely: virgin fabric (silane coupling agent removed), silane-treated (as received fabric), corona-treated virgin fabric and silane- plus corona-treated fabric. Hand layup technique was adopted to make composite plates with [0/90, ±452, 0/90] layup using unsaturated polyester resin as matrix. Mechanical testing methods, such as tensile and bending loading as well as low velocity Izod impact and high velocity impact tests in velocities of 88.5, 108.3 and 144 m/s were conducted. The results showed that, although in lower part of high velocity impact rates, i.e., 88.5 m/s, the panels with fiber fabric treatment of silane plus corona revealed significant increase in ballistic resistance, but in general, it was found that the order of optimum performance for E-glass fiber woven roving surface modification methods are: silane, silane plus corona treatment, virgin fabric and sole corona treatment, respectively. The results further revealed that at impact velocities of 108.3 and 144 m/s, the energy absorptions for the samples with silane treatment are 7.9 and 6.6% higher compared to the samples with silane plus corona discharge treatment (S + C) samples, respectively. Damage assessment revealed higher damage extension in the samples with fiber having silane plus corona discharge treatment. Morphological studies on surface roughness were conducted by SEM analysis. The results correlated well with mechanical and impact results in those samples with higher surface roughness showed better mechanical performance and that silane treatment was the dominant factor in performance.

Full-range load-deflection response of FRP-strengthened RC flexural members anchored with FRP anchors

The flexural resistance of reinforced concrete (RC) members such as beams and slabs can be enhanced by bonding fibre-reinforced polymer (FRP) composite plates to their tension face. The effectiveness of the strengthening can be compromised though by premature debonding failure of the FRP which can occur at strains significantly lower than the strain capacity of the FRP. Anchorage of the FRP strengthening can, however, increase its usable strain. A convenient means with which to represent the structural behaviour of such a strengthened and anchored member then is via its load-deflection response. The task of how to model this response therefore arises. The authors, as well as other research groups, have derived closed-form solutions which describe the complete load-deflection response of FRP-strengthened RC flexural members of which pre-defined moment-curvature relationships are observed. This paper reports an extension to such existing theory in order to incorporate the anchorage effect. The theory is finally calibrated with test results of FRP-strengthened RC slabs which have been anchored with FRP anchors. The paper sets a framework for future work centred on quantification of the FRP anchor effect.

Penetration impact behaviour of hot-compacted self-reinforced polyamide 6 composite laminates

Polyamide 6 based sheets are produced by a typical hot compaction procedure and characterised in terms of compaction quality and penetration low-velocity impact performances. Starting from two commercial clothes, a yellow one fully constituted by PA6 fibres and a hybrid red one containing also 1% of secondary polyurethane fibres, single polymer composite (SPC) plates involving 24, 30 and 36 layers of each fabric were prepared under controlled conditions and studied to define their potential applications. Ultrasonic C-scan results showed a quality of compaction always decreasing with the number of stacked fabric layers (thickness) and, with the same number of cloth layers, lower for red laminates compared to yellow ones, in line with previous morphological observations. Different damage propagation mechanisms occur as highlighted by typical load-deflection curves with hybrid systems showing a more pronounced ductile behaviou and an evident deviation from the penetration energy-thickness linear relationship for red samples is detected.

Dynamic Response of Laminated GFRP Composite under Low Velocity Impact: Experimental and Numerical Study

This paper presents experimental and numerical study of dynamic response of laminated glass fiber reinforced polymer (GFRP) composite plate due to blunt projectile impact considering incidence velocity lower than the ballistic limit. The experimentation of impact tests were performed with pneumatic gun which was used to propel a 52 g cylindrical steel projectile of diameter 19 mm on the laminated composite plate (0°/90°)5 of size 140 mm × 140 mm × 3.12 mm. A three dimensional Finite Element model has also been presented in ANSYS/AUTODYN, a commercial hydro code, considering shock effect of impact in material modeling. The numerical results were validated with actual results. The timehistories of velocity and acceleration of projectile along with the deflection, resistance force, energy absorption and damage pattern in the target plate have been studied. The numerical predictions of damage in the target and velocity history of the projectile show good correlation with the actual results.