Number Of Plies Research Articles

Shape memory polymer composites by molding aeronautical prepregs with shape memory polymer interlayers

Carbon-fiber-reinforced (CFR) and shape-memory polymer (SMP) composites have been manufactured by molding commercial prepregs used for aeronautical structures. These prepregs typically do not show any shape memory behavior as they consist of CF fabrics impregnated with high performance epoxy resins. In the current study, shape memory (SM) properties have been added by using uncured SMP interlayers during the prepreg lamination, and following co-curing of the laminate layers. A new test has been adopted to quantify SM properties of final CFR-SMP laminates. A full thermo-mechanical cycle is applied to the composite samples during bending and shape fixity, shape recovery and frozen stresses data are extracted. By means of this test, the effect of the number of plies on the SM behavior of composite laminates has been studied. Furthermore, dynamic mechanical analysis and dimensional observations have been carried out to understand the physical phenomena at the basis of the laminate behavior. Results show that manufacturing of CFR-SMP composites is feasible also by using available commercial products, and final laminates are able to combine strength and stiffness of traditional aeronautical composites with the functionality of SMP materials.

Optimization of glass epoxy composite driveshaft for light motor vehicles using fuzzy logic technique

ABSTRACT The conventional material used for driveshaft is alloy steel, which has the limitation of strength to weight ratio. The alternative to overcome this limitation is the use of composite materials. The advanced composite materials such as graphite fibre, carbon fibre, Kevlar fibre and glass fibre with suitable resins like epoxy and polyester are widely used because of their high specific strength and high specific module. The composite material has less density, which results in a lightweight composite driveshaft. Reduction in weight of driveshaft increases the transmission efficiency and fuel economy. In this work, the glass epoxy composite driveshaft has been designed for a light passenger vehicle. An attempt has been made to optimise the designed drive shaft using the fuzzy logic technique for the weight minimisation, maximise torsional strength, torsional buckling strength, natural frequency, and critical speed. In this optimisation, the number of plies, the stacking sequence and fibre volume fraction have been considered as the design variables. The manufactured composite drive shaft has been investigated experimentally for its performance. The weight of the developed composite driveshaft is reduced by 74% without having an adverse effect on the required performance.

Experimental and numerical studies on the bending collapse of multi-cell Aluminum/CFRP hybrid tubes

Wrapping the structures with composites and adopting multi-cell sections are two typical methods to improve the crashworthiness of thin-walled beams. However, the effects of combining these two methods on crashworthiness are not clear. This paper aims to investigate the bending collapse and crashworthiness of the multi-cell aluminum/carbon fiber reinforced plastic (Al/CFRP) hybrid tubes under quasi-static and dynamic loading. Three-point bending tests are firstly conducted for the CFRP, Al and Al/CFRP square tubes with single or multi-cell sections. The deformation characteristics and crushing force responses of the tubes are analyzed, and the energy absorption performances are evaluated. The bending resistance of the Al tubes is increased by up to 41% attributed to the CFRP enhancement. The non-linear finite element software ABAQUS/Explicit is then employed to simulate the tests and help analyze the deformation mechanisms. Parametric studies are performed to investigate the influence of the Al wall thickness, the number of CFRP plies, loading velocity, partial wrapping and sectional shape on the crashworthiness of Al/CFRP tubes. Results show that the Al wall thickness, partial wrapping, and sectional shape have a significant influence on the deformation pattern and force response of Al/CFRP tubes, while the number of CFRP plies and the loading velocity have a relatively small influence. The specific energy absorption of Al/CFRP tubes can be increased by 11% by introducing partial CFRP wrapping, and in all cases, the multi-cell Al/CFRP tubes outperform the single-cell counterparts in crashworthiness performances.

SPH-FEM simulation of impacted composite laminates with different layups

Composite laminates offer the potential for reducing the weight of civil aircrafts. However, a major hazard to civil aviation is bird-strike impact damage. In this paper, bird-strike impact damages of composite laminates are numerically investigated by means of Smoothed Particle Hydrodynamics (SPH) and finite element method (FEM) analysis. We mainly focus the influence of laminates' layups on damage modes and energy variations of bird impact on a square laminated plate. The SPH method and an equation of state were employed for the bird projectile. A Continuum Damage Mechanics approach in FEM was applied to simulate failure initiation and damage evolution in composite laminates. Damage maps were calculated with respect to three different layups, i.e. 8 plies, 16 plies and 24 plies, indicating localized damage area as the ply number increased. Deformations of laminates and projectile were studied during the impact damage process. The energy variations (kinetic, strain and damage dissipations) were also comparatively investigated. Results can serve as design guideline in future bird-strike study of composite laminates in complex aircraft structures.

Fabrication of ultrathin-MoS2/Ag/AgBr composite with enhanced photocatalytic activity

The MoS2/Ag/AgBr composite with ultrathin-MoS2 layers was prepared by the methods of ultrasonic liquid exfoliation and ion exchange. The composition and micromorphology of ultrathin-MoS2/Ag/AgBr were detected by XRD, EDS, SEM and TEM in detail. The element mapping showed that the samples were well-distributed. The MoS2 in samples and the number of plies were detected by Raman spectra specifically. The results indicated that the photocatalytic performance of the as-prepared samples would increase by 50% when the average thickness of MoS2 was about 4 nm. The enhanced photocatalytic performance of ultrathin-MoS2/Ag/AgBr composite is attributed to the modified conduction band of MoS2 by reducing the layers of MoS2 to fit the potential of O2/O2·−. In particular, this work would expand the scope of application of MoS2 in photodegradation.

Progressive failure analysis of thick imperfect composite plates using nonlinear plate theory

The work presented here alludes to the application of a semi-analytical method for ultimate strength predictions of square composite plates with geometric imperfections that are subjected to uniaxial in-plane compressive load. The Ritz method is developed with the assumptions of large deflections and higher-order shear deformation theory that accounts for through-the-thickness deformation. Therefore, some thick and relatively thick simply-supported square laminates are analyzed in this study. To obtain the ultimate strength of the plates, we consider two geometric degradation models to assess the degradation zone around the failed location. To predict the first ply failure load and also nonlinear response in the progressive damage analysis, we use the Hashin–Rotem failure criteria. We present results with respect to the number of plies, thickness of the laminates and different magnitudes of imperfection for some symmetric lay-ups.

Optimal design of damage tolerant composite using ply angle dispersion and enhanced bat algorithm

In this work, minimum weight optimization of laminated composite is performed using a newly developed enhanced bat algorithm (EBA). Bat algorithm (BA) is a recently developed swarm-based optimization technique which is inspired by the echolocation behavior of bats. The standard BA shows premature convergence and reduced convergence speeds under some conditions. So, the EBA is used to perform the design optimization of laminated composites. The laminate analysis based on classical laminate theory is utilized for the stress calculations. Tsai–Wu failure curve is considered as the constraint in this constrained optimization problem. Number of plies at each orientation angle are considered as the design variables. The design optimization has been carried out for both conventional and unconventional (dispersed plies) stacking sequences considering different loading configurations: uniaxial tension, biaxial tension with and without shear loadings. Ply angles dispersed in the range of $$5^{\circ }$$–$$85^{\circ }$$, $$25^{\circ }$$–$$65^{\circ }$$ and $$0^{\circ }$$–$$90^{\circ }$$ at intervals of $$5^{\circ }$$ are considered for the unconventional stacking sequence to increase damage tolerance. In addition, a new mathematical function is proposed to measure the dispersion of ply angles in the laminate called the dispersion function. Also, the performance of EBA is compared with standard BA in the optimum weight design of composite laminates.

Tensile characterization of multi‐ply fabric‐reinforced cementitious matrix strengthening systems

AbstractFabric reinforced cementitious matrix (FRCM) is a composite consisted of high‐strength fibers impregnated in a cement‐based mortar, and is commonly used for strengthening reinforced concrete and masonry structures. Comprehending the tensile behavior of FRCM is important to achieve a reliable and accurate design of FRCM strengthening systems. The current paper reports on the results of an experimental study on the tensile characterization of FRCM. A total of 40 FRCM specimens (410 × 50 mm, varied in thickness) were prepared and tested. The tensile characterization tests were conducted according to AC 434 guidelines using clevis‐grip mechanism. The tests were used to assess the effect of two parameters: (a) fabric type (carbon/glass) and (b) number of fabric plies (one/two/three/four). The results showed that the tensile strength of carbon‐FRCM specimens was approximately 1.33 times that of the glass‐FRCM counterparts. Three distinct failure modes were observed, namely, (a) ductile fabric slippage in carbon‐FRCM (up to three plies of fabric); (b) brittle fabric delamination in carbon‐FRCM with four plies of fabric; and (c) brittle fabric rupture in glass‐FRCM systems. The FRCM tensile load‐carrying capacity had proportionally increased with the number of fabric plies; less significant effect (within 20%) was observed on the corresponding ultimate tensile stresses (considering the net fabric area as the effective area).

Retrofitting external RC beam-column joints of an ordinary MRF through plastic hinge relocation using FRP laminates

This paper presents the results of experimental and numerical investigations on flange and web -bonded FRP retrofitting schemes for external RC joints of moment resisting frames. Two, identical full-scale external joints are designed and constructed according to ACI318M-11 requirements for ordinary moment resisting frames. Quasi-static cyclic loading tests are then carried out on the specimens and some seismic performance parameters including strength, ductility, energy dissipation and stiffness are evaluated and compared. Numerical analyses are also carried out to study the effects of FRP overlay length on required number of plies for plastic hinge relocation and joint strength. It is found that successful relocation of plastic hinge away from the face of the column into the beam is possible with appropriate number of FRP laminate plies and overlay length. It is also found that as the length of the FRP laminate over the beam flange increases, the joint strength is enhanced; however, larger number of plies would be required for plastic hinge relocation.

Redundancy and robustness of brittle laminated plates. Overlooked aspects in structural glass

It is a consolidated belief that the reliability of brittle plates is increased using laminated layers instead of a monolith: redundancy permits stress redistribution after partial breakage. To quantify this effect, the retro-cumulative function of plate strength is calculated for inflected laminates with a variable number of plies using the failure modes approach. The material is elastic perfectly-brittle and its strength may be characterized by different statistics, implying either volume-size-effect, area-size-effect, or no-size-effect. The plate is analysed in limit conditions for what concerns the capability of the adhesive layers to transfer shear stresses. Robustness is discussed by assuming that an accidental event may break one of the plies.The type of size-effect plays a decisive role. Under the same maximum tensile stress in the sound state, lamination is always beneficial only for volume-size-effect. For area-size-effect, the negative effect of the new surface from lamination is counterbalanced by stress redistribution only for the lower quantiles of the strength distribution. The same is true under an accidental event. With no-size-effect, the gain from lamination is again appreciable only at low failure probabilities. These findings raise questions about the positive effects of lamination for structural glass, strongly characterized by an area size effect.

Effect of matrix material and orientation angle on tensile and tribological behavior of jute reinforced composites

Abstract Environmental friendly natural fibers have been used instead of petroleum-based synthetic fibers as reinforcements because of the depletion of oil resources, plastic waste disposal problems and the emissions generated during combustion. In these natural fibers, thermoplastic or thermoset materials are used as matrix material because of their low cost, light weight and durability. In this study, the effects of ply number (2 and 3 layer) and orientation angle of reinforcement (0/90° and ± 45°) and matrix type (thermoset and thermoplastic) on the tensile strength of jute reinforced composites were investigated. Also, the effect of the reinforcement orientation angle, sliding time (600, 1200 and 1800 s) and applied load (5, 10 and 15 N) on tribological characteristics were determined. Adhesive and abrasion wear tests were carried out at 0.15 m × s−1 sliding speed. It was observed that the matrix material and the reinforcement are very important in tensile and wear tests, while the ply number and the orientation angle only exert an influence in the tensile strength of composites. It was determined that an increase in load and sliding time is the most effective parameter on wear experiments.

Computational multi-scale analysis of simultaneous processes of delamination and damage accumulation in laminated composites

When studying mechanical behavior of structures made of laminated polymer composite materials, issues related to their relatively high susceptibility to damage, such as delamination, fiber breakage and matrix failure, play significant role. Key aspects are also related to accurate description of the internal structures and heterogeneity of the material. This work is aimed at a numerical study of the processes of damage accumulation in plies as well as development of delamination in laminated polymer composite L-shaped specimen taking into account microstructural parameters. The influence of contact conditions between the plies on the model’s behavior has been studied. It was established that the delamination processes inside the specimen can initiate at the early stages of deformation, which is reflected in the difference of the results obtained using models with various numbers of separated plies. Comparison of the results of modelled elastic behavior of the specimen and models with the developed delamination leads to conclusions about influence of a number of model parameters on the results obtained before and after propagation of delamination. In particular, such factors as the geometry and mechanical properties of models, the number and conditions for specifying contact pairs in the model were analyzed.

Hybrid Metal/Composite Lattice Structures: Design for Additive Manufacturing

This paper introduces a numerical tool developed for the design and optimization of axial-symmetrical hybrid composite/metal structures. It is assumed that the defined structures are produced by means of two different processes: Additive Layer Manufacturing (ALM) for the metallic parts and Filament Winding (FW) for the composite parts. The defined optimization procedure involves two specific software: ANSYS and ModeFrontier. The former is dedicated to the production of the geometrical and FE models, to the structural analysis, and to the post-process, focusing on the definition of the Unit Cells for the modelling of the metal part. The latter is dedicated to the definition of the best design set and thus to the optimization flow management. The core of the developed numerical procedure is the routine based on the Ansys Parametric Design Language (APDL), which allows an automatic generation of any geometrical model defined by a generic design set. The developed procedure is able to choose the best design, in terms of structural performance, changing the lattice metallic parameters (number of unit cells and their topology) and the composite parameters (number of plies and their orientation). The introduced numerical tool has been used to design several hybrid structures configurations. These configurations have been analysed in terms of mechanical behaviour under specific boundary conditions and compared to similar conventional metal structure.

Modelling the size and strength benefits of optimised step/scarf joints and repairs in composite structures

Adhesive bonding offers a better load transfer between adherends, for the assembly and repair of composite structures, compared with mechanical fastening methods. One drawback of adhesive bonded repairs is the considerable amount of material which must be removed, around the damaged region, to ensure adequate load transfer. Optimised geometries that account for the highly-orthotropic properties of individual composite plies are investigated, including a novel ‘fibre-oriented’ scarf approach that is inspired by an existing fibre-oriented step design. These methods aim to reduce the length of joint and repair bonding regions by at least 36%, compared with conventional step and scarf geometries of a similar strength.Size-reduction benefits are predicted using a MATLAB tool that is applicable for any composite laminate, and parametric analysis used to assess the effect of ply thickness, the number of plies, stacking sequence and taper angle.Cohesive Zone Models of joints and repairs with conventional and fibre-oriented designs are used to predict and compare the ultimate strength of each configuration. The existing fibre-oriented step design appears to show no benefit over a conventional step design. However, the novel fibre-oriented scarf approach results in a 33–40% reduction in the size of the bonding region compared to a conventional scarf design with similar strength. Analysis further indicates a 17–22% increase in ultimate strength for joints and repairs with the same bonding region size that employ the optimised fibre-oriented scarf design.

Influence of thread count of carbon twill textile-reinforced polyamide 66 laminates on the inductive heating behavior

This study addresses the experimental investigation of the influence of the thread count of carbon fiber (CF) twill textile-reinforced polyamide 66 laminates on their inductive heating behavior. By means of stationary heating experiments of laminates, different twill 2/2 fabrics have been investigated. The used twill 2/2 fabrics differ only in thread count and consequently in their area weight. Due to the different area weight, the manufactured laminates differ in the number of plies to guarantee an equal fiber volume content in each plate. In order to evaluate the heating behavior of the different specimens, the heating rates of both surfaces of the specimens were measured and compared. Thus, it was found that a lower thread count promotes a faster inductive heating of CF twill 2/2-reinforced polymer composites. Further investigations based on microsection analysis and measurements of rovings cross-section shape revealed that the increase of heating rates at lower thread counts relies more on the number of fabric layers. Through a higher number of fabric layers, the total contact area will be higher due to more interply and intraply contact interfaces which occur in the laminate.

An elliptical model for lockstitch 301 seam to estimate thread consumption

A geometrical model for lockstitch seam 301 has been proposed based on elliptical profile to estimate the thread consumption. The realistic elliptical shape of a lockstitch 301 seam has been confirmed by observing cut section along seam line. In order to validate a model across the different fabric types, varieties of fabrics from woven shirting, woven jeans, knitted single jersey to nonwoven interlining fabric have been considered. The different number of plies (2, 3 and 4) of given fabrics have been stitched at different levels of stitch densities (3, 4 and 5 stitches per cm) to observe effects in prediction of these parameters. It is found that the error % is increasing with increase in stitch density and number of ply. The proposed elliptical model have been compared with other recent rectangular profile based models, it is found that the propose model is more accurate and generalised with less error %, as compared to other models across the different fabric types. Also there is a strong correlation obtained between practical (actual) thread consumption and predicted from model.

Lateral strength and ductility of reinforced concrete columns strengthened with NSM FRP rebars and FRP jacket

Fiber-reinforced polymer (FRP) wrapping of reinforced concrete (RC) columns is an effective way to improve their shear capacity and ductility and prevent buckling in their longitudinal reinforcements. Another strengthening method called the near surface mounted (NSM) reinforcement has been proven effective in improving the flexural strength of RC columns. In this research, the strengthening of RC columns with the combined use of NSM rebars and FRP jacket was studied using a finite element modeling approach. After validating the numerical models with the existing experimental data, a comprehensive parametric study was performed to determine the effect of axial load, implementing the FRP confinement around the base or over the entire height of the column, the number of plies of FRP jacket, the type of jacket fiber, the ratio of NSM reinforcement, and the compressive strength of the concrete on the behavior of the strengthened RC columns. The results show that the optimum number of plies of jacket for reaching a desirable level of ductility can be determined by setting the maximum compressive strain in the confined concrete, varepsilon_{text{ccu}}, to 0.008. Increasing the ratio of NSM reinforcement from 0.16% of the total cross-sectional area to 1% led to approximately 28% increase in the lateral strength and 50% decrease in the ductility factor.

Review and Analysis of Various Composite Propeller Shaft

The replacement of conventional steel driveshaft of automobiles with an appropriate composite driveshaft with different combinations of fibers at a time. For reducing the bending natural frequency the conventional steel shafts are made in two pieces, where to reduce the overall weight the composite material drive shaft is made in single piece. Various composites can be designed and analyzed for their appropriateness in terms of torsional strength, bending natural frequency and torsional buckling by comparing them with the conventional steel driveshaft under the same grounds of design constraints and the best-suited composite will be recommended. Light has been thrown upon the aspects like mass saving, number of plies and ply distribution.

Processing of metallic fiber hybrid spun yarns for better electrical conductivity

ABSTRACTThis research was aimed at processing of metallic fiber hybrid spun yarns consisting of polyester/stainless steel and viscose/stainless steel staple fibers to achieve better electrical conductivity. Conventional ring spinning machine and ring twister machine were used to produce the single and plied yarns respectively. The linear electrical resistance of yarns was analyzed with reference to the three levels of twist multiplier (TM) for same yarn count, three levels of yarn fineness (Ne) at the same TM level, and number of plies for the same final yarn count. These results showed that by increasing twist, the electrical conductivity of yarn was increased. However, yarn fineness was in inverse relation with the electrical conductivity of yarns. The effect of yarn plying and twisting to produce the Ne 10s yarn was also found critical in governing the electrical properties. The electrical conductivity of viscose and stainless steel hybrid yarn was found more sensitive to increase with an increase in relative humidity contrary to that of polyester and stainless steel hybrid yarns. The findings of the study are significant to produce the hybrid spun conductive yarns for their potential applications in a variety of tailor-made functional, protective and smart textiles.

Polymer composite Belleville springs for an automotive application

This paper investigates mathematical modelling and manufacturing of polymer composite Belleville springs, and their potential application. The original expression for load carrying capacity developed for metal springs is refined by considering the variation of elastic modulus and Poisson’s ratio of laminates in polar coordinates. A novel series spring stacking arrangement is proposed to achieve complex stiffness variation by progressive action. The experimental results show consistent effect of number of plies on the spring rate and compare well with the theoretical predictions. Although handmade, the variations in load carrying capacity is very small (∼10%) confirming manufacturing viability. It is shown that a smooth, variable spring rate curve can be produced by reducing slip-stick frictional forces with the use of spacers within the spring stacks. In one application, the composite springs are shown to offer significant vehicle dynamic performance improvement through reduction of the tyre contact patch force variation and vehicle body acceleration.