Search results

1 – 10 of 917
Click here to view access options
Article
Publication date: 25 February 2014

Shiuh-Chuan Her and Shou-Jan Liu

Carbon nanotubes (CNTs) with exceptional mechanical, thermal and electrical properties are considered to be ideal for reinforcing high-performance structures. The…

Abstract

Purpose

Carbon nanotubes (CNTs) with exceptional mechanical, thermal and electrical properties are considered to be ideal for reinforcing high-performance structures. The interfacial stresses between the CNTs and surrounding matrix are important phenomena which critically govern the mechanical properties of CNTs-reinforced nanocomposites. A number of methods have been proposed to investigate the stress transfer across the CNT/matrix interface, such as experimental measurement and molecular dynamics (MDs). Experimental tests are difficulty and expensive. MDs simulations, on the other hand, are computationally inefficient. The purpose of this paper is to present a reasonably simplified model. Incorporating the simplified model, the analytical expressions of the interface stresses including the shear stress and longitudinal normal stress are obtained.

Design/methodology/approach

The analytical model consists of two concentric cylinders, namely a single-walled carbon nanotube (SWCNT) cylinder and a matrix cylinder, as the representative volume element (RVE). The interfacial stress analysis is performed using the shear lag model for the axisymmetric RVE. Analytical solutions for the normal stresses in the SWCNT and matrix, and the interfacial shear stress across the SWCNT/matrix interface are obtained. The proposed model has a great ability to theoretical prediction of the stress transfer between the matrix and CNTs.

Findings

In order to demonstrate the simulation capabilities of the proposed model, parametric studies are conducted to investigate the effects of the volume fraction of SWCNT and matrix modulus on the stress transfer. The axial stress in the matrix is decreasing with the increase of the volume fraction and decrease of the matrix modulus. As a result of more loads can be transferred to the SWCNT for a large volume fraction and small matrix modulus. These results show that using a large volume fraction and a small matrix modulus improves the efficiency of the stress transfer from the matrix to the CNTs.

Originality/value

A simple but accurate model using a simplified 2D RVE for characterizing the stress transfer in CNT-reinforced nanocomposites is presented. The predictions from the current method compare favourably with those by existing experimental, analytical and computational studies. The simple and explicit expressions of the interfacial stresses provide valuable analysis tools accessible to practical users.

Details

Engineering Computations, vol. 31 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Click here to view access options
Article
Publication date: 5 May 2015

Babruvahan Pandurang Ronge and Prashant Maruti Pawar

– This paper aims to focus on the stochastic analysis of composite rotor blades with matrix cracking in forward flight condition.

Abstract

Purpose

This paper aims to focus on the stochastic analysis of composite rotor blades with matrix cracking in forward flight condition.

Design/methodology/approach

The effect of matrix cracking and uncertainties are introduced to the aeroelastic analysis through the cross-sectional stiffness properties obtained using thin-walled beam formulation, which is based on a mixed force and a displacement method. Forward flight analysis is carried out using an aeroelastic analysis methodology developed for composite rotor blades based on the finite element method in space and time. The effects of matrix cracking are introduced through the changes in the extension, extension-bending and bending matrices of composites, whereas the effect of uncertainties are introduced through the stochastic properties obtained from previous experimental and analytical studies.

Findings

The stochastic behavior of helicopter hub loads, blade root forces and blade tip responses are obtained for different crack densities. Further, assuming the behavior of progressive damage in same beam is measurable as compared to its undamaged state, the stochastic behaviors of delta values of various measurements are studied. From the stochastic analysis of forward flight behavior of composite rotor blades at various matrix cracking levels, it is observed that the histograms of these behaviors get mixed due to uncertainties. This analysis brings out the parameters which can be used for effective prediction of matrix cracking level under various uncertainties.

Practical implications

The behavior is useful for the development of a realistic online matrix crack prediction system.

Originality/value

Instead of introducing the white noise in the simulated data for testing the robustness of damage prediction algorithm, a systematic approach is developed to model uncertainties along with damage in forward flight simulation.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 87 no. 3
Type: Research Article
ISSN: 0002-2667

Keywords

Click here to view access options
Article
Publication date: 8 August 2016

Vladimir Kobelev

The purpose of this paper is to introduce the double-periodic lattice, composed of bending-resistant fibers. The essence of the model is that the filaments are of infinite…

Abstract

Purpose

The purpose of this paper is to introduce the double-periodic lattice, composed of bending-resistant fibers. The essence of the model is that the filaments are of infinite length and withstand tension and bending. The constitutive equations of the lattice in discrete and differential formulations are derived. Two complementary systems of loads, which cause different deformation two orthogonal families of fibers, occur in the lattice. The fracture behavior of the material containing a semi-infinite crack is investigated. The crack problem reduces to the exactly solvable Riemann-Hilbert problem. The solution demonstrates that the behavior of material cardinally depends upon the tension in the orthogonal family of fibers. If tension in fibers exists, opening of the crack under action of loads in two-dimensional lattice is similar to those in elastic solid. In the absence of tension, contrarily, there is a finite angle between edges at the crack tip.

Design/methodology/approach

The description of stress state in the crack vicinity is reduced to the solution of mixed boundary value problem for simultaneous difference equations. In terms of Fourier images for unknown functions the problem is equivalent to a certain Riemann-Hilbert problem.

Findings

The analytical solution of the problem shows that fracture behavior of the material depends upon the presence of stabilizing tension in fibers, parallel to crack direction. In the presence of tension in parallel fibers fracture character of two-dimensional lattice is similar to behavior of elastic solid. In this case the condition of crack grows can be formulated in terms of critical stress intensity factor. Otherwise, in the absence of stabilizing tension, the crack surfaces form a finite angle at the tip.

Research limitations/implications

Linear behavior of fibers until rupture. Small deflections. Perfect two-dimensional lattice.

Practical implications

The model provides exact analytical estimation of stresses on the crack tip as the function of fibers’ stiffness.

Originality/value

The model is the extension of known lattice models, taking into account the semi-infinite crack in the lattice. This is the first known closed form solution for an infinite lattice model with the crack.

Details

Multidiscipline Modeling in Materials and Structures, vol. 12 no. 2
Type: Research Article
ISSN: 1573-6105

Keywords

Click here to view access options
Article
Publication date: 1 October 2005

D. Roy Mahapatra, S. Suresh, S.N. Omkar and S. Gopalakrishnan

To develop a new method for estimation of damage configuration in composite laminate structure using acoustic wave propagation signal and a reduction‐prediction neural…

Abstract

Purpose

To develop a new method for estimation of damage configuration in composite laminate structure using acoustic wave propagation signal and a reduction‐prediction neural network to deal with high dimensional spectral data.

Design/methodology/approach

A reduction‐prediction network, which is a combination of an independent component analysis (ICA) and a multi‐layer perceptron (MLP) neural network, is proposed to quantify the damage state related to transverse matrix cracking in composite laminates using acoustic wave propagation model. Given the Fourier spectral response of the damaged structure under frequency band‐selective excitation, the problem is posed as a parameter estimation problem. The parameters are the stiffness degradation factors, location and approximate size of the stiffness‐degraded zone. A micro‐mechanics model based on damage evolution criteria is incorporated in a spectral finite element model (SFEM) for beam type structure to study the effect of transverse matrix crack density on the acoustic wave response. Spectral data generated by using this model is used in training and testing the network. The ICA network called as the reduction network, reduces the dimensionality of the broad‐band spectral data for training and testing and sends its output as input to the MLP network. The MLP network, in turn, predicts the damage parameters.

Findings

Numerical demonstration shows that the developed network can efficiently handle high dimensional spectral data and estimate the damage state, damage location and size accurately.

Research limitations/implications

Only numerical validation based on a damage model is reported in absence of experimental data. Uncertainties during actual online health monitoring may produce errors in the network output. Fault‐tolerance issues are not attempted. The method needs to be tested using measured spectral data using multiple sensors and wide variety of damages.

Practical implications

The developed network and estimation methodology can be employed in practical structural monitoring system, such as for monitoring critical composite structure components in aircrafts, spacecrafts and marine vehicles.

Originality/value

A new method is reported in the paper, which employs the previous works of the authors on SFEM and neural network. The paper addresses the important problem of high data dimensionality, which is of significant importance from practical engineering application viewpoint.

Details

Engineering Computations, vol. 22 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Click here to view access options
Article
Publication date: 10 July 2007

Shantanu C. Prabhune and Ramesh Talreja

To provide a basis for making assessment of the safety of adhesively bonded joints after they have been de‐painted by a dry abrasive method or a wet chemical method.

Abstract

Purpose

To provide a basis for making assessment of the safety of adhesively bonded joints after they have been de‐painted by a dry abrasive method or a wet chemical method.

Design/methodology/approach

Stress analysis by a finite element method has been conducted for metal/composite and composite/composite joints in a single lap configuration. The effects of degradation of composite and adhesive, separately or combined, on the stresses in the adhesive layer bonding the two components are studied. Effects of wet and dry conditions of de‐painting are included in the study. It is assumed that in the composite these conditions affect only the laminae close to the surface from which the paint coating is removed.

Findings

The locations and values of the maximum peel and shear stresses in the adhesive are determined for both joints under different assumed conditions of degradation caused by de‐painting.

Research limitations/implications

Experimental data indicating the extent of surface damage caused by de‐painting is not available.

Originality/value

Extensive literature study did not show any investigation of composite surface damage and adhesive property degradation on integrity of adhesively bonded joints. Results reported here will be of use in assessing effects of de‐painting on the structural performance of adhesively bonded joints.

Details

Aircraft Engineering and Aerospace Technology, vol. 79 no. 4
Type: Research Article
ISSN: 0002-2667

Keywords

Click here to view access options
Article
Publication date: 2 February 2015

Kamil Janeczek, Małgorzata Jakubowska, Grażyna Kozioł and Anna Młożniak

The purpose of this paper is to examine electrical and mechanical properties of radio frequency identification (RFID) chip joints assembled on a flexible substrate and…

Downloads
250

Abstract

Purpose

The purpose of this paper is to examine electrical and mechanical properties of radio frequency identification (RFID) chip joints assembled on a flexible substrate and made from isotropic conductive adhesives (ICAs) reinforced with graphene nanoplatelets (GPNs) or graphite nanofibers (GFNs).

Design/methodology/approach

The ICAs reinforced with GPNs or GFNs were prepared and screen printed on a test pattern to investigate resistance and thickness of these adhesive layers. Differential Scanning Calorimetry (DSC) was performed to assess a curing behaviour of the prepared ICAs. Then, RFID chips were mounted with the prepared ICAs to the pattern of silver tracks prepared on foil. Shear test was carried out to evaluate mechanical durability of the created chip joints, and resistance measurements were carried out to evaluate electrical properties of the tested ICAs.

Findings

The 0.5 per cent (by weight) addition of GFNs or GPNs to the ICA improved shear force values of the assembled RFID chip joints, whereas resistance of these modified adhesives increased. The DSC analysis showed that a processing temperature of the tested adhesives may range from 80 to 170°C with different curing times. It revealed a crucial influence of curing time and temperature on electrical and mechanical properties of the tested chip joints. When the chip pads were cured for too long (i.e. 60 minutes), it resulted in a resistance increase and shear force decrease of the chip joints. In turn, the increase of curing temperature from 80 to 120°C entailed improvement of electrical and mechanical properties of the assembled chips. It was also found that a failure location changed from the chip – adhesive interface towards the adhesive – substrate one when the curing temperature and time were increased.

Research limitations/implications

Further investigations are required to examine changes thoroughly in the adhesive reinforced with GFNs after a growth of curing time. It could also be worth studying electrical and mechanical properties of the conductive adhesive with a different amount of GFNs or GPNs.

Practical implications

The tested conductive adhesive reinforced with GFNs or GPNs can be applied in the production of RFID tags because it may enhance the mechanical properties of tags fabricated on flexible substrates.

Originality/value

Influence of GFNs and GPNs on the electrical and mechanical properties of commercial ICAs was investigated. These properties were also examined depending on a curing time and temperature. New conductive materials were proposed and tested for a chip assembly process in fabrication of RFID tags on flexible substrates.

Details

Soldering & Surface Mount Technology, vol. 27 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Click here to view access options
Article
Publication date: 1 March 2007

Tomohiro Yokozeki

Gas permeability through damage networks in composite laminates is the key issue for the applicability of high‐performance composites to the cryogenic propellant tanks of…

Abstract

Gas permeability through damage networks in composite laminates is the key issue for the applicability of high‐performance composites to the cryogenic propellant tanks of space launch vehicles. A simple model for the gas permeability induced by multilayer matrix cracks in composite laminates is proposed based on the leak conductance at crack intersections, which is an extension of the model by Kumazawa et al (AIAA J. 41, 2037‐ ‐2044, 2003). Experimental evidence on the gas permeability mechanisms is summarized and reflected in the present model. In order to include the effects of applied loadings and damage sizes on the gas permeability, the leak conductance is assumed to be a function of the average crack opening displacements of the matrix cracks and the crack intersection angles. The leak conductance factor was empirically obtained as a function of the crack intersection angle, and the comparison of the gas permeability between the predictions based on the developed model and the experimental results is presented for the validity of this model.

Details

Multidiscipline Modeling in Materials and Structures, vol. 3 no. 3
Type: Research Article
ISSN: 1573-6105

Keywords

Click here to view access options
Article
Publication date: 16 April 2018

Fábio Monteiro Conde, Pedro Gonçalves Coelho, Rodrigo Paiva Tavares, Pedro Castro Camanho, José Miranda Guedes and Helder Carriço Rodrigues

This study aims to achieve a “pseudo-ductile” behaviour in the response of hybrid fibre reinforced composites under uniaxial traction by solving properly formulated…

Downloads
117

Abstract

Purpose

This study aims to achieve a “pseudo-ductile” behaviour in the response of hybrid fibre reinforced composites under uniaxial traction by solving properly formulated optimization problems.

Design/methodology/approach

The composite material model is based on the combination of different types of fibres (with different failure strains or strengths) embedded in a polymer matrix. The composite failure under tensile load is predicted by analytical models. An optimization problem formulation is proposed and a Genetic Algorithm is used. Multi-objective optimization problems balancing failure strength and ductility criteria are solved providing optimal mixtures of fibres whose properties may come either from a pre-defined list of materials, currently available in the market, or simply assuming their continuum variation within predefined bounds, in an attempt to attain unprecedented performance levels.

Findings

Optimal solutions of hybrid fibre reinforced composites exhibiting pseudo-ductile behaviour are presented. It is found that a fibre made from a material exhibiting relatively low stiffness combined with high strength is preferred for hybridization. Furthermore, the ratio of the average failure/critical strains between the low and high elongation fibres to be hybridized must be equal or greater than two.

Originality/value

Typically, a ductile failure is an inherent property of metals, that is, their typical response curve after the linear (elastic) region exhibits a yielding plateau still followed by an increase in stress till collapse. In stark contrast, composite materials exhibit (under some loading conditions) brittle failure that may limit their widespread usage. Therefore, a “pseudo-ductility” in composites is valued and targeted through optimization which is the main original contribution here.

Details

Engineering Computations, vol. 35 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Click here to view access options
Article
Publication date: 8 February 2016

Zhihong Du, Xinhua Ni, Xiequan Liu and Cheng Chen

According to the microstructural characteristics of composite ceramic, the strain field distribution regularity of triangular symmetrical composite eutectic is obtained…

Abstract

Purpose

According to the microstructural characteristics of composite ceramic, the strain field distribution regularity of triangular symmetrical composite eutectic is obtained from the stress field distribution regularity of three-phase element in composite ceramic. In allusion to the damage of composite eutectic, it is introduced as a variable in this paper with the aim to determine the strain field distribution regularity of triangular symmetrical composite eutectic with damage behavior.

Design/methodology/approach

On the basis of the relationship between strain field and fiber inclusions volume fraction, the strain field of composite eutectic is analyzed.

Findings

The strain field of composite ceramic is distinctly dependent on the fiber inclusions volume fraction, fiber diameter and damage behavior of composite eutectic by quantitative analysis. The strain in matrix parallel to eutectic is the maximum linear strain and the main factor for the damage and fracture of eutectics.

Originality/value

The foundation of the strength research of composite eutectic is laid.

Details

World Journal of Engineering, vol. 13 no. 1
Type: Research Article
ISSN: 1708-5284

Keywords

Click here to view access options
Article
Publication date: 6 March 2017

Yuxiu Yan, Yanna Feng, Zimin Jin and Jianwei Tao

The purpose of this paper is to improve the comfort and shaping function of seamless shapewear on the material and structure and develop new seamless shapewear products…

Abstract

Purpose

The purpose of this paper is to improve the comfort and shaping function of seamless shapewear on the material and structure and develop new seamless shapewear products. The shaping figure effect will be verified as well.

Design/methodology/approach

The performance of the knitted fabrics made of Polytrimethylene terephthalate (PTT) filament was analyzed by orthogonal experiment and fuzzy mathematical methods analysis, in order to get the optimal conditions for the best performance. The new products were designed and made based on the results of the material research with the consideration of the aesthetic requirements. The shaping effect of seamless shapewears on local and global figure was tested by the methods of the combination of subjective and objective evaluation.

Findings

The sample which renders the optimal performance for shapewear is the one with PTT filament as face yarn, nylon core-spun yarn as ground yarn and 3+1 simulate rib knit structure. The material of face yarn, mixed proportion and structure can influence the shape retention, appearance and comfort of PTT fabric in various degrees. Three shapewears which were developed according to the results of material research have different shaping effect. And women with different figures put different satisfaction degrees on each shapewear’s shaping effect.

Practical implications

This paper provides scientific basis and reference for enterprise to design good tight seamless shapewear as well as for consumer to buy suitable products.

Originality/value

In the view of the problems of present shapewears, this paper completed the development of the shapewears and verified the shaping effect of them on women with different figures. The shapewears can be put into production directly.

Details

International Journal of Clothing Science and Technology, vol. 29 no. 1
Type: Research Article
ISSN: 0955-6222

Keywords

1 – 10 of 917