Fiber Composite Plate Research Articles

Impact imaging of aircraft composite structure based on a model-independent spatial-wavenumber filter

The spatial-wavenumber filtering technique is an effective approach to distinguish the propagating direction and wave mode of Lamb wave in spatial-wavenumber domain. Therefore, it has been gradually studied for damage evaluation in recent years. But for on-line impact monitoring in practical application, the main problem is how to realize the spatial-wavenumber filtering of impact signal when the wavenumber of high spatial resolution cannot be measured or the accurate wavenumber curve cannot be modeled. In this paper, a new model-independent spatial-wavenumber filter based impact imaging method is proposed. In this method, a 2D cross-shaped array constructed by two linear piezoelectric (PZT) sensor arrays is used to acquire impact signal on-line. The continuous complex Shannon wavelet transform is adopted to extract the frequency narrowband signals from the frequency wideband impact response signals of the PZT sensors. A model-independent spatial-wavenumber filter is designed based on the spatial-wavenumber filtering technique. Based on the designed filter, a wavenumber searching and best match mechanism is proposed to implement the spatial-wavenumber filtering of the frequency narrowband signals without modeling, which can be used to obtain a wavenumber-time image of the impact relative to a linear PZT sensor array. By using the two wavenumber-time images of the 2D cross-shaped array, the impact direction can be estimated without blind angle. The impact distance relative to the 2D cross-shaped array can be calculated by using the difference of time-of-flight between the frequency narrowband signals of two different central frequencies and the corresponding group velocities. The validations performed on a carbon fiber composite laminate plate and an aircraft composite oil tank show a good impact localization accuracy of the model-independent spatial-wavenumber filter based impact imaging method.

Development of High Strength Natural Fibre based Composite Plates for Potential Application in Retrofitting of RC Structure

The potential application of green fibre based composite plate in retrofitting of structure is growing up in construction industry nowadays. The aim of this research was to develop high strength natural fibre based composite plates for the possible application in strengthening of reinforced concrete structure. The plates were fabricated using kenaf fibre, jute fibre and jute rope respectively. The fibres and rope were chemically treated using 6% NaOH solution to enhance the tensile strength of fabricated plates. In fabrication process, a special technique was applied to compact the treated and untreated fibres to obtain the highest tensile strength of composite plates. The physical and mechanical properties of the fabricated composite plates were then experimentally investigated. In general, results showed that the chemical treatments had an influence to enhance the tensile strength of the plates. The tensile strength of composite plates with treated kenaf fibre, jute fibre and jute rope were 137 MPa, 136 MPa and 113 MPa respectively. While those of untreated kenaf fibre, jute fibre and jute ropes were 131 MPa, 136 MPa and 110 MPa respectively. Kenaf and jute fibre composite plates had shown higher tensile strengths as compared to those of jute rope. The natural fibre composite plates were found to be linearly elastic in nature and had shown brittle failure. The moisture content and the water absorption of the plates with treated fibres were found to be lower as compared to those of untreated fibres. In terms of tensile strength of fabricated plates, kenaf, jute and jute rope composite plates could be used in retrofitting of structures.

An improved two-dimensional multiple signal classification approach for impact localization on a composite structure

Efficient impact monitoring techniques are important to be researched to ensure the safety of in-service composite structures. Multiple signal classification–based method is a new promising method. This method uses small aperture sensor array arrangement instead of sparse sensor arrangement. It has the advantage of easy sensor array arrangement. By processing the whole sensor array outputs using the multiple signal classification algorithm, transfer function and material property of the structure are not needed. Although some researches have shown the potential of this new method, most of the current researches have been performed based on the far-field assumption on aluminum structures. In engineering applications, composite structures are the main structures which need impact monitoring. Deep research needs to be addressed. Aiming at these problems, an improved two-dimensional near-field multiple signal classification processing algorithm is presented for impact localization on composite structure in this article. The proposed method can simultaneously estimate the impact occurring direction and distance. A uniform carbon fiber composite plate and a real aircraft oil tank made of carbon composite structure with varied thickness are adopted to evaluate the presented method. To deal with the anisotropy performance of the complex composite, the two-dimensional multiple signal classification processing algorithm is also improved by taking into account the existing anisotropy performance.

Ultimate Load of Three-Layered Annular Fibrous Composite Plate Fastened on Internal and Simply Supported External Contours

A load-carrying capacity of the three-layered annular plate fastened on internal and simply supported external contours has been investigated. As viewed from front face the plate has a coating with thin layers where interlayer is reinforced with fibers. It is assumed that the material of matrix, fibers and coatings is ideally rigidly plastic without hardening and their properties differ in tension and compression, whereas fibers in coating are so thin that their dimensions in the cross section can be neglected. It is accepted that the contact between the matrix, coating and fiber is ideal. It is shown that the plates are divided into four annular zones, within each of which different plastic state is realized. Static moment fields and kinematic field of velocities of bending are determined, the equations for determination of the unknown radii dividing different plastic zones as well as for support reaction and ultimate load in case of uniformly distributed lateral load are found.

The effects of stacking sequence on the penetration-resistant behaviors of T800 carbon fiber composite plates under low-velocity impact loading

Impact damages induced by a low-velocity impact load on carbon fiber reinforced polymer (CFRP) composite plates fabricated with various stacking sequences were studied experimentally. The impact responses of the CFRP composite plates were significantly affected by the laminate stacking sequences. Three types of specimens, specifically quasi-isotropic, unidirectional, and cross-ply, were tested by a constant impact carrying the same impact energy level. An impact load of 3.44 kg, corresponding to 23.62 J, was applied to the center of each plate supported at the boundaries. The unidirectional composite plate showed the worst impact resistance and broke completely into two parts; this was followed by the quasi-isotropic lay-up plate that was perforated by the impact. The cross-ply composite plate exhibited the best resistance to the low-velocity impact load; in this case, the impactor bounced back. Impact parameters such as the peak impact force and absorbed energy were evaluated and compared for the impact resistant characterization of the composites made by different stacking sequences.

Free Vibration of Woven Fiber Composite Angular Plates in Adverse Hygrothermal Environment

Free Vibration of Woven Fiber Composite Angular Plates in Adverse Hygrothermal Environment

Development of Hybrid Jute Fibre Composite Plates for Potential Application in Shear Retrofitting of RC Structure

Application of natural fibre based composite plate in retrofitting of structure is the current interest of construction industry. This paper presents the finding of an experimental study on jute rope fibre hybrid composite plates for potential application in shear strengthening of RC beam. In the experimental programme, hybrid composite plates had been fabricated using jute rope and carbon fibres with five different mixes i.e. 45% jute rope with 0% carbon; 43% jute rope with 2.5% carbon; 41% jute rope with 5% carbon; 41% jute rope with 7.5% carbon and 39% jute rope with 10% carbon.The physical and mechanical properties of the fabricated hybrid composite plates were thenexperimentally investigated. Results showed thatcarbon contents had an influence to enhance the tensile strength of the plates. Hybrid composite plate with 10% carbon content had shown 170% higher tensile strength as compared to that of plate without carbon fibre. The carbon content also had enhanced the modulus of elasticity of plates. Higher percentage of carbon had shown higher tensile strength and modulus of elasticity of hybrid composite plates.All fabricated plates had linear elastic properties under tension. The density of plates increased with the increasing of carbon content in composite plates. The research findings indicated that the developed hybrid composite jute rope could be used for shearstrengthening of reinforced concrete beam.

Modal Analysis of Woven Fiber Composite Plates with Different Boundary Conditions

Most of the work done for the vibration of composite plates published in the literature is either analytical or numerical studies with few experimental results available on composites with unidirectional fibers. The present study involves extensive experimental works to investigate the free vibration of industry driven woven fiber glass/epoxy composite plates with different boundary conditions including free–free cases. The modern modal testing and subsequent analysis with powerful computer and digital analysis system is an important tool for prediction of behavior of structures. The specimens of woven glass fiber and epoxy matrix composite plates are manufactured by the hand-layup technique. Elastic parameters of the plate are also determined experimentally by tensile testing of specimens using INSTRON 1195. An experimental investigation is carried out using modal analysis technique with Fast Fourier Transform Analyzer, PULSE lab shop, impact hammer and contact accelerometer to obtain the frequency response functions. The computational results are compared with results of previous studies in literature wherever available. The experimental results are also compared with the FEM numerical analysis based on first-order shear deformation theory. The effects of different geometrical parameters including number of layers, aspect ratio, fiber orientation and different boundary conditions of woven fiber composite plates are studied in detail. It is observed that comparisons performed between numerical predictions and experimental tests have a good correlation. The natural frequency is very less for cantilever than simply supported and fully clamped boundary conditions. The prediction of dynamic behavior of laminated composite plates plays a significant role in the future applications of structural composites.

J1010202 曲線状強化繊維を有する複合材の生産性と力学強度に関する多目的最適化

The present study proposes a multi-objective optimization method of productivity and dynamic strength for the fibrous composite plate with curvilinear fibers. The fibrous composites have some problems in the practical application to structures. The productivity decreases and fiber density becomes nonuniform with increase in the maximum curvature of curvilinear fibers. Therefore, the relationships between the productivity and curvature are formulated by the experimental results and a practical optimum curvilinear fiber shapes are searched. Curvilinear fiber shapes are defined by the coefficients of the cubic polynomial function. Because principal strains are important in design of aircraft main wings, principal strains of the plate are calculated by the finite element method with eight-node quadrilateral isoparametric element. An Optimized Multi-Objective Particle Swarm Optimization (OMOPSO) based on the non-dominated sorting and crowded distance metric sorting is employed as an optimizer with an inertia weight controlled by the auto-tuning method. The numerical results showed that the present optimization considering the relationships between the density and curvature resulted in the more practical solutions than the previous solutions.

Effect of inter-layer toughness in ballistic protection systems on absorption of projectile energy

This paper concerns absorption of the kinetic energy of a projectile in multi-layer protection systems, with particular focus on the role of inter-layer bonding. Two-layer samples have been produced, composed of a 2 mm thick alumina front plate and a carbon fibre composite back plate with a thickness of about 0.8 mm. These were manufactured under two sets of conditions. The fracture energy of the inter-layer interface was measured for these two types of sample to be 170 and 620 J m−2. Such samples were subjected to impact by spherical projectiles of hardened steel, with a diameter of 8 mm and an impact speed of about 220 m s−1, corresponding to a kinetic energy of about 50 J. Samples composed of the alumina plate alone and of unbonded alumina and composite layers were also tested. It was found that significantly more projectile energy was absorbed by the strongly bonded samples, and that this difference was greater than could be explained solely in terms of the interfacial debonding energy. This is investigated by estimating the magnitudes of all of the identifiable sources of energy absorption, including that of plastic deformation of the projectile. It is concluded that strong inter-layer bonding can promote greater energy absorption in the composite back-plate.

Yield Hypersurfaces of a Three-Layer Composite Shell With a Fiber-Reinforced Middle Layer

Plastic yield conditions for three-layer fibrous composite shells and plates, whose middle layer (matrix) is reiforced with thin fibers and outer ones (coverings) are homogeneous and isotropic, are determined. It is assumed that the matrix, fibers, and coverings are perfectly plastic (without hardening) and their properties in tension and compression are different. The fibers and coverings are thin to an extent their transverse dimensions can be neglected. The contact between the covering and matrix and between the matrix and fibers is perfect. It is also assumed that neutral surfaces arise in the construction, whose strain rate grows linearly with distance from the surfaces. Expressions for the yield hypersurfaces in terms of bending moments and membrane forces are derived.

Multiple damage detection on aircraft composite structures using near-field MUSIC algorithm

Damages in composite structure can lead to significant reduction in local strengths. Therefore, it is important to localize these damages to give an early warning for maintenance of the aircraft. Since these damages may happen near the sensor array, the wave fronts are spherical and the far-field multiple signal classification (MUSIC) based methods with the plane wave hypothesis are no longer valid. Aimed at developing MUSIC algorithm to detect near-field damages, a new near-field 2D-MUSIC method using piezoelectric sensor array is presented first. Though ordinary MUSIC algorithms can be used to distinguish multiple sources, they request the signals from these sources are independent with each other. By using the active damage monitoring method, since all damage scattered signals are the damage reflection signals of the same active excitation one, they are all correlated. This gives rise to the difficulty to apply ordinary MUSIC methods to detect multiple damages in the structure using active monitoring approach. To distinguish multiple damages in the structure, a correlated near-field 2D-MUSIC method based on spatial smoothing algorithm is also proposed to solve the correlation problem of multiple damage detection. To verify the proposed methods, evaluation experiments are performed on a carbon fiber composite material plate and a real aircraft composite oil tank. The results prove the effectiveness of the presented methods to detect multiple damages on the complex composite structure.

Impact Experiment and Analysis of the Carbon Fiber Composite Plate with the Central Hole

The composite material plate with the central hole is made by the composite prepreg. During the laying, the circle Teflon sheet is installed into the center of the composite plate. After curing, the center circle area was cut-out and the composite plate with the central hole was observed. Three different central holes are designed by the diameter of 12 mm, 14 mm, and 16 mm. The composite plate with central hole is stroke by the impact-or to measure the absorption energy, and acceleration to compare their impact resistance. The finite element analysis is also used to analyze the mechanical behavior of the plate during and after the impact. The results showed that the energy absorption capability is lower when the central hole became bigger.

Experimental investigation of damping flexural vibrations in glass fibre composite plates containing one- and two-dimensional acoustic black holes

In this paper, the results of the experimental investigation into the addition of indentations of power-law profile into composite plates and panels and their subsequent inclusion into composite honeycomb sandwich panels are reported. The composite plates in question are sheets of composite with visible indentations of power-law profile. A panel is a sheet of composite with the indentations encased within the sample. This makes a panel similar in surface texture to an un-machined composite sheet (reference plate) or conventional honeycomb sandwich panel. In the case of quadratic or higher-order profiles, the above-mentioned indentations act as two-dimensional acoustic black holes for flexural waves that can absorb a large proportion of the incident wave energy. For all the composite samples tested in this investigation, the addition of two-dimensional acoustic black holes resulted in further increase in damping of resonant vibrations, in addition to the already substantial inherent damping due to large values of the loss factor for composites. Due to large values of the loss factor for composite materials used, there was no need in adding small pieces of absorbing layers to the indentations to achieve desirable levels of damping.

Surface modifications of gasketless carbon composite bipolar plates for gas tightness of PEM fuel cells

A carbon fiber composite gasketless bipolar plate for proton exchange membrane (PEM) fuel cells was developed using the groove of a trapezoidal shape, which develops large contact stresses due to a wedge mechanism. The surface of the composite groove was modified to increase gas tightness without using rubber gaskets. Graphite, polyimide (PI) and polyethylene terephthalate (PET) film were co-cure bonded on the surface of the bipolar plate during the compression molding process to change its surface hardness, which could affect the gas tightness. Additionally, plasma surface treatment and mechanical abrasion were used to modify the surface morphologies. Corrosion and gas tightness tests on the surface modified bipolar plates were performed to verify the reliability of the gasketless sealing method.

The effect of shear strength on the ballistic response of laminated composite plates

Abstract The ballistic performance of clamped circular carbon fibre reinforced polymer (CFRP) and Ultra High Molecular Weight Polyethylene (UHMWPE) fibre composite plates of equal areal mass and 0/90° lay-up were measured and compared with that of monolithic 304 stainless steel plates. The effect of matrix shear strength upon the dynamic response was explored by testing: (i) CFRP plates with both a cured and uncured matrix and (ii) UHMWPE laminates with identical fibres but with two matrices of different shear strength. The response of these plates when subjected to mid-span, normal impact by a steel ball was measured via a dynamic high speed shadow moire technique. Travelling hinges emanate from the impact location and travel towards the supports. The anisotropic nature of the composite plate results in the hinges travelling fastest along the fibre directions and this results in square-shaped moire fringes in the 0/90° plates. Projectile penetration of the UHMWPE and the uncured CFRP plates occurs in a progressive manner, such that the number of failed plies increases with increasing velocity. The cured CFRP plate, of high matrix shear strength, fails by cone-crack formation at low velocities, and at higher velocities by a combination of cone-crack formation and communition of plies beneath the projectile. On an equal areal mass basis, the low shear strength UHMWPE plate has the highest ballistic limit followed by the high matrix shear strength UHMWPE plate, the uncured CFRP, the steel plate and finally the cured CFRP plate. We demonstrate that the high shear strength UHMWPE plate exhibits Cunniff-type ballistic limit scaling. However, the observed Cunniff velocity is significantly lower than that estimated from the laminate properties. The data presented here reveals that the Cunniff velocity is limited in its ability to characterise the ballistic performance of fibre composite plates as this velocity is independent of the shear properties of the composites: the ballistic limit of fibre composite plates increases with decreasing matrix shear strength for both CFRP and UHMWPE plates.

Influence of Filler Materials on Pinned Joints of Woven Glass Fiber Reinforced Epoxy Composites

Fiber reinforced composite materials have been gaining wide application in aircraft submarine and spacecraft constructions, to strengthen bridges and other civil engineering structures. Joints are formed using mechanical fasteners and load sharing in these joints depends on the number, size, and material of the bolts and the stiffness of the joining members. Therefore, suitable revealing methods for the failure strength would help in selecting the appropriate joint size in a given application. The objective of the present work is to determine the bearing or failure load of filler added woven glass fiber/epoxy composites through single and double serial pinned joints with different parameters by experimental methods. The effect of the distance from free edge to the diameter of first hole (E/D) ratio, the width of plate to diameter of hole (W/D) ratio and the effect of filler materials on Titanium dioxide (TiO2) and Zinc Sulphide (ZnS) on bearing load are experimentally investigated using laminated woven glass fiber composite plate with single and double serial pinned joints.

Improved strain sensing performance of glass fiber polymer composites with embedded pre-stretched polyvinyl alcohol–carbon nanotube fibers

Polyvinyl alcohol–carbon nanotube (PVA–CNT) fibers differing on their pre-stretching condition were embedded in glass fiber reinforced plastic (GFRP) composites and used as strain sensors for damage monitoring of the composite. Strain sensing of the composite was made by the in situ measurement of the embedded fiber’s electrical resistance change during the mechanical tests. Four glass fiber composite plates were manufactured; each one had embedded a different type of produced PVA–CNT fibers. The multi-functional materials were tested in monotonic tensile tests as well as in progressive damage accumulation tests. The electrical resistance readings of the PVA–CNT fibers were correlated with axial strain values, taking into account the induced damage of the composite. It has been demonstrated that increasing the fiber’s pre-stretching ratio, its electrical resistance response increases due to higher degree of the CNTs alignment in the PVA matrix. Higher fiber pre-stretching degree enables the better strain monitoring of the composite due to higher measured electrical resistance change values noticed for the same applied axial strain values. To this end, it enables for the better monitoring of the progressive damage accumulation inside the composite.

Non-Destructive Technique for Determination of Elastic Material Properties

An inverse technique, based on the planning of experiments and response surface methodology have been applied to determine elastic properties of unidirectional carbon fiber composite plate and carbon nanotubes reinforced aluminium plate. The nuances of application of investigated technique for orthotropic material properties determination are considered on the example of a composite plate. In turn, possibility of using of this technique on specimens with small dimensions (80x60x2 mm) is checked up and estimated on an example of an isotropic nanocomposite plate. The results obtained were verified by comparing the experimentally measured eigenfrequencies with numerical ones obtained by FEM using determinated elastic material properties. has been employed in (4), but the minimization method was different. Instead of the direct minimization of the functional, the experiment design and response surface approach are employed for approximation of the numerical (finite element) model. Such an approach can reduce the computational efforts significantly. In order to reduce the computational efforts, methods based on the approximation concepts were used in the structural optimization for the first time (5). The development of approximation functions has become a separate problem in optimum structural design. Approximating models can be built in different ways. To construct a more general model of the original function, the methods of experiment design (6) and approximate model building (7) can be used. A simplified model, called a meta-model (8), is elaborated using results of the numerical experiment at a sample point of the experiment design. The response analysis using the simplified model is computationally much cheaper than the solution employing the original model. II. NUMERICAL-EXPERIMENTAL METHOD

Multiscale modeling of matrix cracking coupled with interfacial debonding in random glass fiber composites based on volume elements

A multiscale numerical approach is established to model damage in random glass fiber composites. A representative volume element of a random glass fiber composite is employed to analyze microscale damage mechanisms, such as matrix cracking and fiber-matrix interfacial debonding, while the associated damage variables are defined and applied in a mesoscale stiffness reduction law. The macroscopic response of the homogenized mesoscale damage model is investigated using finite element analysis and validated through experiments. A case study of a random glass fiber composite plate containing a central hole subjected to tensile loading is performed to illustrate the applicability of the multiscale damage model.