CERES :: Browsing by Author "Khan, Kamran Ahmed"

Browsing by Author "Khan, Kamran Ahmed"

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Open Access
3-3 piezoelectric metamaterial with negative and zero Poisson's ratio for hydrophones applications
(Elsevier, 2018-12-18) Khan, Kamran Ahmed; Khan, Muhammad Ali
This study presents the electromechanical properties of the 3-3 piezoelectric metamaterial based on variants of honeycomb (HC) structure. Three kinds of three-dimensional (3D) elastically anisotropic and piezoelectrically active HC structures were introduced, namely, conventional HC (3D-CHC), a re-entrant HC (3D-RE) and a semi-re-entrant HC (3D-SRE). Highly porous 3D finite element models of the mentioned three kinds of metamaterials were developed and the role of ligament orientation on their effective elastic, piezoelectric and dielectric properties was completely characterized. The intrinsic symmetry of HC structure was utilized and simplified mixed boundary conditions equivalent to periodic boundary conditions were recognized. In comparison to their bulk constituent, all the 3-3 type piezoelectric HC networks exhibited an enhanced response, especially for the longitudinal poling. The normalized figures of merit show a mild dependence on the angle θ and the underlying deformation mechanisms associated with the zero, positive and negative Poisson’s ratios. Figures of merit such as hydrostatic strain coefficient (dh" role="presentation">), the hydrostatic figure of merit (dh.gh" role="presentation">) and the acoustic impedance (Z" role="presentation">) reached their best values at small angles, i.e., θ = 30°. Longitudinally poled networks exhibited four order of magnitude increase in their hydrostatic figure of merit (foam to solid ratio >10,000) and one order of magnitude decrease in the acoustic impedance indicating their applicability for the design of hydrophones.
Open Access
Analytical and numerical assessment of the effect of highly conductive inclusions distribution on the thermal conductivity of particulate composites
(SAGE, 2019-04-10) Khan, Kamran Ahmed; Hajeri, Falah Al; Khan, Muhammad A.
Highly conductive composites have found applications in thermal management, and the effective thermal conductivity plays a vital role in understanding the thermo-mechanical behavior of advanced composites. Experimental studies show that when highly conductive inclusions embedded in a polymeric matrix the particle forms conductive chain that drastically increase the effective thermal conductivity of two-phase particulate composites. In this study, we introduce a random network three dimensional (3D) percolation model which closely represent the experimentally observed scenario of the formation of the conductive chain by spherical particles. The prediction of the effective thermal conductivity obtained from percolation models is compared with the conventional micromechanical models of particulate composites having the cubical arrangement, the hexagonal arrangement and the random distribution of the spheres. In addition to that, the capabilities of predicting the effective thermal conductivity of a composite by different analytical models, micromechanical models, and, numerical models are also discussed and compared with the experimental data available in the literature. The results showed that random network percolation models give reasonable estimates of the effective thermal conductivity of the highly conductive particulate composites only in some cases. It is found that the developed percolation models perfectly represent the case of conduction through a composite containing randomly suspended interacting spheres and yield effective thermal conductivity results close to Jeffery's model. It is concluded that a more refined random network percolation model with the directional conductive chain of spheres should be developed to predict the effective thermal conductivity of advanced composites containing highly conductive inclusions.
Open Access
Experimental and numerical study of the effect of silica filler on the tensile strength of a 3D-printed particulate nanocomposite
(Elsevier, 2019-09-03) Asif, Muhammad Usman; Ramezani, Maziar; Khan, Kamran Ahmed; Khan, Muhammad Ali; Aw, Kean Chin
Polymers are commonly found to have low mechanical properties, e.g., low stiffness and low strength. To improve the mechanical properties of polymers, various types of fillers have been added. These fillers can be either micro- or nano-sized; however; nano-sized fillers are found to be more efficient in improving the mechanical properties than micro-sized fillers. In this research, we have analysed the mechanical behaviour of silica reinforced nanocomposites printed by using a new 5-axis photopolymer extrusion 3D printing technique. The printer has 3 translational axes and 2 rotational axes, which enables it to print free-standing objects. Since this is a new technique and in order to characterise the mechanical properties of the nanocomposites manufactured using this new technique, we carried out experimental and numerical analyses. We added a nano-sized silica filler to enhance the properties of a 3D printed photopolymer. Different concentrations of the filler were added and their effects on mechanical properties were studied by conducting uniaxial tensile tests. We observed an improvement in mechanical properties following the addition of the nano-sized filler. In order to observe the tensile strength, dog-bone samples using a new photopolymer extrusion printing technique were prepared. A viscoelastic model was developed and stress relaxation tests were conducted on the photopolymer in order to calibrate the viscoelastic parameters. The developed computational model of nano reinforced polymer composite takes into account the nanostructure and the dispersion of the nanoparticles. Hyper and viscoelastic phenomena was considered to validate and analyse the stress–strain relationship in the cases of filler concentrations of 8%, 9%, and 10%. In order to represent the nanostructure, a 3D representative volume element (RVE) was utilized and subsequent simulations were run in the commercial finite element package ABAQUS. The results acquired in this study could lead to a better understanding of the mechanical characteristics of the nanoparticle reinforced composite, manufactured using a new photopolymer extrusion 5-axis 3D printing technique.
Open Access
Fracture life estimation of Al-1050 thin beams using empirical data and a numerical approach
(British Institute of Non-destructive Testing, 2018-07-01) Khan, Muhammad Ali; Khan, Kamran Ahmed; Nisar, Salman; Starr, Andrew
A technique based on empirical data and finite element (FE) analysis to predict the fracture life of Al-1050 beams with the help of its fundamental mode is presented in this study. Experiments were performed on a non-prismatic beam vibrating with a constant value of the amplitude at the fixed end until the complete fracture of the specimen was achieved. The beam was vibrating at its fundamental mode to achieve fracture in less time. A power law model was used to acquire the possible trends between the values of natural frequencies and the number of cycles recorded during these experiments. These trends were further compared with a numerically modelled specimen but with artificial cracks. FE modal analysis was used for this comparison. An error of less than 1% was observed in the estimated number of total cycles obtained through the power law model before fracture, compared to those obtained using the numerical approach. Using this approach, the fracture life was also predicted for specimens of different lengths.
Open Access
Frequency and amplitude measurement of a cantilever beam using image processing: with a feedback system
(IEEE, 2019-03-18) Khan, Sohaib Z.; Qazi, Sallar; Nisar, Salman; Khan, Muhammad A.; Khan, Kamran Ahmed; Rasheed, Farrauk; Farhan, Muhammad
Image processing techniques can be utilized in analyzing amplitude and frequency of vibrating structures. It is a form of non-contact method which is suitable for cases where application of contact devices could alter the frequency of structure. This paper covers the study based on vision system that performs amplitude and frequency measurement of a cantilever beam in near real time, using image processing and computer vision toolbox in MATLAB. The vision system then detects changes in amplitude followed by feedback mechanism to ensure operation at resonance frequency. The system includes a high speed camera which is able to detect amplitude and frequency of cantilever beam vibrating at a frequency with the help of mechanical exciter. The high speed camera captures images of the beam, that are processed by a MATLAB script for evaluation of amplitude and frequency. To locate amplitude of the vibrating beam, centroid recognition technique is used which tracks the centroids of the beam in consecutive frames and plots number of pixels moved by the centroid with respect to time. Later, frequency is found out on the basis of intensity change over the time. Amplitude analysis is done at different frequencies which are automatically adjusted with the help of microcontroller to determine the resonance point. Exciter continues to vibrate at the resonant frequency until a change in amplitude is detected, implying the formation of crack. At which point the system adjusts its vibrating frequency accordingly to adjust with the new resonant frequency. This paper covers proper experimental procedure backed with the results.
Open Access
Gear misalignment diagnosis using statistical features of vibration and airborne sound spectrums
(Elsevier, 2019-05-31) Khan, Muhammad Ali; Shahid, Muhammad Atayyab; Ahmed, Syed Adil; Khan, Sohaib Zia; Khan, Kamran Ahmed; Ali, Syed Asad; Tariq, Muhammad
Failure in gears, transmission shafts and drivetrains is very critical in machineries such as aircrafts and helicopters. Real time condition monitoring of these components, using predictive maintenance techniques is hence a proactive task. For effective power transmission and maximum service life, gears are required to remain in prefect alignment but this task is just beyond the bounds of possibility. These components are flexible, thus even if perfect alignment is achieved, random dynamic forces can cause shafts to bend causing gear misalignments. This paper investigates the change in energy levels and statistical parameters including Kurtosis and Skewness of gear mesh vibration and airborne sound signals when subjected to lateral and angular shaft misalignments. Novel regression models are proposed after validation that can be used to predict the degree and type of shaft misalignment, provided the relative change in signal RMS from an aligned condition to any misaligned condition is known.
Open Access
Identification of an effective nondestructive technique for bond defect determination in laminate composites - a technical review
(SAGE, 2018-03-29) Asif, Muhammad; Khan, Muhammad Ahmed; Khan, Sohaib Z.; Choudhry, Rizwan S.; Khan, Kamran Ahmed
Laminate composites are commonly used for the production of critical mechanical structures and components such as wind turbine blades, helicopter rotors, unmanned aerial vehicle wings and honeycomb structures for aircraft wings. During the manufacturing process of these composite structures, zones or areas with weak bond strength are always issues, which may affect the strength and performance of components. The identification and quantification of these zones are always challenging and necessary for the mass production. Non-destructive testing methods available, including ultrasonic A, B, and C-Scan, laser shearography, X-ray tomography, and thermography can be useful for the mentioned purposes. A comparison of these techniques concerning their capacity of identification and quantification of bond defects; however, still needs a comprehensive review. In this paper, a detailed comparison of several non-destructive testing techniques is provided. Emphasis is placed to institute a guideline to select the most suitable technique for the identification of zones with bond defects in laminated composites. Experimental tests on different composite based machined components are also discussed in detail. The discussion provides practical evidence about the effectiveness of different non-destructive testing techniques.
Open Access
In-situ dynamic response measurement for damage quantification of 3D printed ABS cantilever beam under thermomechanical load
(MDPI, 2019-12-12) Baqasah, Hamzah; He, Feiyang; Zai, Behzad A.; Asif, Muhammad; Khan, Kamran Ahmed; Thakur, Vijay Kumar; Khan, Muhammad A.
Acrylonitrile butadiene styrene (ABS) offers good mechanical properties and is effective in use to make polymeric structures for industrial applications. It is one of the most common raw material used for printing structures with fused deposition modeling (FDM). However, most of its properties and behavior are known under quasi-static loading conditions. These are suitable to design ABS structures for applications that are operated under static or dead loads. Still, comprehensive research is required to determine the properties and behavior of ABS structures under dynamic loads, especially in the presence of temperature more than the ambient. The presented research was an effort mainly to provide any evidence about the structural behavior and damage resistance of ABS material if operated under dynamic load conditions coupled with relatively high-temperature values. A non-prismatic fixed-free cantilever ABS beam was used in this study. The beam specimens were manufactured with a 3D printer based on FDM. A total of 190 specimens were tested with a combination of different temperatures, initial seeded damage or crack, and crack location values. The structural dynamic response, crack propagation, crack depth quantification, and their changes due to applied temperature were investigated by using analytical, numerical, and experimental approaches. In experiments, a combination of the modal exciter and heat mats was used to apply the dynamic loads on the beam structure with different temperature values. The response measurement and crack propagation behavior were monitored with the instrumentation, including a 200× microscope, accelerometer, and a laser vibrometer. The obtained findings could be used as an in-situ damage assessment tool to predict crack depth in an ABS beam as a function of dynamic response and applied temperature.
Open Access
Instant dynamic response measurements for crack monitoring in metallic beams
(British Institute of Non-destructive Testing, 2019-04-01) Zai, Behzad Ahmed; Khan, Muhammad A.; Mansoor, Asif; Khan, Sohaib Z.; Khan, Kamran Ahmed
This paper investigates the interdependencies of the modal behaviour of a cantilever beam, its dynamic response and crack growth. A methodology is proposed that can predict crack growth in a metallic beam using only its dynamic response. Analytical and numerical relationships are formulated between the fundamental mode and crack growth using the existing literature and finite element analysis (FEA) software, respectively. A relationship between the dynamic response and the modal behaviour is formulated empirically. All three relationships are used to predict crack growth and propagation. The load conditions are considered the same in all of the experiments for both model development and model validation. The predicted crack growth is compared with the visual observations. The overall error is within acceptable limits in all comparisons. The results obtained demonstrate the possibility of diagnosing crack growth in metallic beams at any instant within the operational conditions and environment.
Open Access
Investigation of the strain-rate-dependent mechanical behavior of a photopolymer matrix composite with fumed nano-silica filler
(Wiley, 2019-06-21) Asif, Muhammad; Ramezani, Maziar; Khan, Kamran Ahmed; Khan, Muhammad Ali; Aw, Kean Chin
With the evolution of additive manufacturing, there is an increasing demand to produce high strength and stiffness polymers. Photopolymers are very commonly used in stereolithography and fused deposition modeling processes, but their application is limited due to their low strength and stiffness values. Nano‐sized fibers or particles are generally embedded in the polymer matrix to enhance their properties. In this study, we have studied the effect of fumed nano‐sized silica filler on the elastic and viscoelastic properties of the photopolymer. The uniaxial testing coupons with different concentrations of silica filler have been fabricated via casting. We observed improvement in mechanical properties by the addition of the nano‐sized filler. As polymers exhibit time‐dependent mechanical response, we have conducted tensile tests at different strain rates as it is one of the most common modes of deformation, and is commonly used to characterize the parameters of the rate‐dependent material. We noticed significant dependence of the mechanical properties on the strain rate. quasi‐linear viscoelastic (QLV) model, which combines hyperelastic and viscoelastic phenomena, has been employed to capture the response of the material at different strain rates. We found out that the QLV model with Yeoh strain energy density function adequately describes the rate‐dependent behavior of the material and has reasonable agreement with the experimental results.
Open Access
Low-velocity impact characterization of fiber-reinforced composites with hygrothermal effect
(ASTM, 2018-06-19) Zai, Behzad Ahmed; Khan, Muhammad; Park, M. K.; Shahzad, Majid; Shahzad, M. A.; Salman, Nisar; Khan, Sohaib Zia; Khan, Kamran Ahmed; Shah, Aqueel
In this article, low-velocity impact characteristics of UHN125C carbon fiber/epoxy composite, including unidirectional (0°), cross-directional (0°/90°), and quasi-isotropic layups, were experimentally measured. The effect of the fiber orientation angle and stacking sequences on impact force and induced strain were measured via an instrumented drop-weight apparatus with special concern for the moisture absorption effect. Dried specimens were immersed in distilled water for a certain period of time to absorb water for intermediate and saturated moisture content. It was observed that the impulse was reduced with the increase in moisture content; on the other hand, strain increased with moisture, as measured by DBU-120A strain-indicating software (MADSER Corp., El Paso, TX). Impact damage is widely recognized as one of the most detrimental damage forms in composite laminates because it dissipates the incident energy by a combination of matrix damage, fiber fracture, and fiber-matrix debonding. Therefore, it is extremely important to know the impact strength of a structure, especially for applications in industries such as aerospace, ship design, and some other commercial applications. The use of composite materials in engineering applications is increasing rapidly because they have higher strength-to-weight ratios than metals. The strength, stiffness, and, eventually, the life of composite materials are affected more than conventional materials by the presence of moisture and temperature. Thus, it is necessary to analyze the response of composites in a hydrothermal environment.
Open Access
A machine learning approach to model interdependencies between dynamic response and crack propagation
(MDPI, 2020-11-30) Fleet, Thomas; Kamei, Khangamlung; He, Feiyang; Khan, Muhammad A.; Khan, Kamran Ahmed; Starr, Andrew
Accurate damage detection in engineering structures is a critical part of structural health monitoring. A variety of non-destructive inspection methods has been employed to detect the presence and severity of the damage. In this research, machine learning (ML) algorithms are used to assess the dynamic response of the system. It can predict the damage severity, damage location, and fundamental behaviour of the system. Fatigue damage data of aluminium and ABS under coupled mechanical loads at different temperatures are used to train the model. The model shows that natural frequency and temperature appear to be the most important predictive features for aluminium. It appears to be dominated by natural frequency and tip amplitude for ABS. The results also show that the position of the crack along the specimen appears to be of little importance for either material, allowing simultaneous prediction of location and damage severity
Open Access
A methodology for flexibility analysis of pipeline systems
(SAGE, 2018-12-17) Zahid, Umer; Khan, Sohaib Z.; Khan, Muhammad A.; Bukhari, Hassan J.; Nisar, Salman; Khan, Kamran Ahmed
Pipeline systems serve a crucial role in an effective transport of fluids to the designated location for medium to long span of distances. Owing to its paramount economic significance, pipeline design field have undergone extensive development over the past few years for enhancing the optimization and transport efficiency. This research paper attempts to propose a methodology for flexibility analysis of pipeline systems through employing contemporary computational tools and practices. A methodical procedure is developed, which involves modeling of the selected pipeline system in CAESAR II followed by the insertion of pipe supports and restraints. The specific location and selection of the inserted supports is based on the results derived from the displacement, stress, reaction, and nozzle analysis of the concerned pipeline system. Emphasis is laid on the compliance of the design features to the leading code of pipeline transportation systems for liquid and slurries, ASME B31.4. The discussed procedure and approach can be successfully adjusted for the analysis of various other types of pipeline system configuration. In addition to the provision of systematic flow in analysis, the method also improves efficient time-saving practices in the pipeline stress analysis.
Open Access
A methodology for flexibility analysis of process piping
(SAGE, 2017-11-02) Zahid, Umer; Khan, Sohaib Z.; Khan, Muhammad A.; Bukhari, Hassan J.; Ahmed, Imran; Khan, Kamran Ahmed
Design of piping system requires a systematic consideration of various factors as addressed by the codes and standards. This research paper aims to provide a method for flexibility analysis of a selected area of process piping at an industrial plant. Analysis is done for the purpose of accommodating a spare heat exchanger in the process layout. The analysis follows a systematic procedure, with preparation of a tentative model of the system on CAESAR II software followed by insertion of different pipe supports. The selection and location of these supports is based on the results obtained from displacement, stress, reaction and equipment nozzle analysis of the piping system. The design is in accordance with ASME B31.3, which is the standard code for process piping. The proposed method can be adapted for piping configuration of any industrial plant. With the provision of a systematic procedure, the method ensures time saving and efficient flexibility analysis of any piping system.
Open Access
Micromechanical modeling approach with simplified boundary conditions to compute electromechanical properties of architected piezoelectric composites
(IOP Publishing, 2021-01-14) Khan, Kamran Ahmed; AlHajeri, Falah; Khan, Muhammad
Architected piezoelectric composites (PCs) have recently gained interest in designing transducers and nondestructive testing devices. The current analytical modeling approach cannot be readily applied to design architected periodic PCs exhibiting elastic anisotropy and piezoelectric activity. This study presents a micromechanical (MM)-model based finite element (FE) modeling framework to predict the electromechanical properties (EMPs) of the architected PCs. As an example, the microstructure with one-dimensional (1-3 PCs) connectivity is considered with different cross-sections of fibers. 3D FE models are developed. The intrinsic symmetry of architected composite is used to derive boundary conditions equivalent to periodic boundary conditions (PBCs). The proposed approach is simple and eliminates the need for a tedious mesh generation process on opposite boundary faces on the MM model of architected PCs. The EMPs of 1-3 PCs calculated from the proposed micromechanics-FE models were compared with those obtained from analytical solutions (i.e. based on micromechanics theories), and FE homogenization (i.e. obtained by employing the PBCs available in the literature). A quite good agreement between the proposed modeling approach and the ones obtained using the analytical model was observed. However, an excellent agreement is observed with the MM results that employed PBCs. Hence, we have concluded that the proposed MM modeling approach is equivalent to MM models that employed PBCs. The computed enhanced effective elastic, piezoelectric, and dielectric properties and corresponding figure of merit (FOM) revealed that 1-3 PCs are suitable in transducer applications.
Open Access
Micromechanical modeling of architected piezoelectric foam with simplified boundary conditions for hydrophone applications
(SAGE, 2021-01-05) Khan, Kamran Ahmed; Alarafati, Hamad K.; Khan, Muhammad Ali
Architected piezoelectric materials with controlled porosity are of interest for applications such as hydrophones, miniature accelerometers, vibratory sensors, and contact microphones. Current analytical modeling approach cannot be readily applied to design architected periodic piezoelectric foams with tunable properties while exhibiting elastic anisotropy and piezoelectric activity. This study presents micromechanical-finite element (FE) models to characterize the electromechanical properties of architected piezoelectric foams. The microstructure with zero-dimension (3-0 foam, spherical porosity) and one-dimensional (3-1 foam, cylindrical porosity) connectivity were considered to analyze the effect of porosity connectivity on the performance of piezoelectric foam. 3D FE models of the 3-0 and 3-1 foams were developed and using the intrinsic symmetry of porous structures simplified mixed boundary conditions (MBCs) equivalent to periodic boundary conditions (PBC) were proposed. The proposed approach is simple and eliminates the need of tedious mesh generation process on opposite boundary faces on the micromechanical model of porous microstructures with PBCs. The results obtained from the proposed micromechanics-FE models were compared with those obtained by means of the analytical models based on micromechanics theories, and FE models with PBCs reported in the literature for both 3-0 and 3-1 type foams. An excellent agreement was observed. The computed effective elastic, piezoelectric and dielectric properties and corresponding figure of merit (FOM) revealed that piezoelectric foams with 3-0 connectivity exhibit enhanced hydrostatic FOM as compared to piezoelectric foams with 3-1 connectivity. It is concluded that spherical porosity is more suitable to hydrophone applications.
Open Access
A novel approach for damage quantification using the dynamic response of a metallic beam under thermo-mechanical loads
(Elsevier, 2019-12-06) Zai, Behzad Ahmed; Khan, Muhammad A.; Khan, Kamran Ahmed; Mansoor, Asif
This paper investigates the interdependencies of crack depth and crack location on the dynamic response of a cantilever beam under thermo-mechanical loads. Temperature can influence the stiffness of the structure, thus, the change in stiffness can lead to variation in frequency, damping and amplitude response. These variations are used as key parameters to quantify damage of Aluminum 2024 specimen under thermo-mechanical loads. Experiments are performed on cantilever beams at non-heating (room temperature) and elevated temperature, i.e., 50 °C, 100 °C, 150 °C and 200 °C. This study considers a cantilever beam having various initially seeded crack depth and locations. The analytical, numerical and experimental results for all configurations are found in good agreement. Dynamic response formulation is presented experimentally on beam for the first time under thermo-mechanical loads. Using available experimental data, a novel tool is formulated for in-situ damage assessment in the metallic structures. This tool can quantify and locate damage using the dynamic response and temperature including the diagnosis of subsurface cracking. The obtained results demonstrate the possibility to diagnose the crack growth at any instant within the operational condition under thermo-mechanical loads.
Open Access
A novel twofold symmetry architected metamaterials with high compressibility and negative Poisson's ratio
(Wiley, 2021-02-28) Khan, Kamran Ahmed; Alshaer, Mohammad H.; Khan, Muhammad Ali
This study presents the compression response of additively manufactured novel soft porous structures with architected microstructure. Six porous additively manufactured architected periodic structures with two‐fold and four‐fold symmetry were considered. The effect of pore shape and fold symmetry of microstructure on the non‐linear response of a square array of architected pores in a soft polymeric matrix is experimentally investigated. The digital image correlation (DIC) is used for investigating the evolution of strains and deformation during uniaxial tensile tests and compression tests of porous structures. Compression induced instability lead to negative Poisson's ratio, and compaction of porous structures, which is found to depend not only on the shape of the architecture but also the fold symmetry exists in the microstructure's unit cell. Unique architectures with multiple buckling modes and shape transformation are also observed. Two‐fold symmetry structures are found to buckle at lower strains compared to the four‐fold symmetric structure at the same porosity level and produced high compaction and negative Poisson's ratio. The results showed that in addition to pore shape, the fold symmetry could be used effectively to design a new class of soft, active, and reconfigurable devices over a wide range of length scales with desired characteristics.
Open Access
Performance of engineered fibre reinforced concrete (EFRC) under different load regimes: a review
(Elsevier, 2021-09-17) Khalel, Hamad Hasan Zedan; Khan, Muhammad; Starr, Andrew; Khan, Kamran Ahmed; Muhammad, Asif
This review article presents a critical analysis by compiling the previous research studies with an emphasis on the optimization of fibre reinforced concrete to enhance its strength against different load regimes with a special focus on thermo-mechanical load conditions. The historical background, a description of the evolution of concrete as a material for advanced structures, and the fundamental principles of concrete production are provided as a preamble. Later, a discussion on FRC, fibre types and shapes, mixing methods and testing of properties is provided. A separate section describes how fibre mixing can affect fatigue and fracture behaviour, especially under different load regimes. Gaps in the existing research with possible new directions are discussed in the conclusion
Open Access
Predicting the effect of voids on mechanical properties of woven composites
(IOP, 2018-09-21) Choudhry, R. S.; Sharif, Tahir; Khan, Kamran Ahmed; Khan, Sohaib Z.; Hassan, Abid; Khan, Muhammad Ali
An accurate yet easy to use methodology for determining the effective mechanical properties of woven fabric reinforced composites is presented. The approach involves generating a representative unit cell geometry based on randomly selected 2D orthogonal slices from a 3D X-ray micro-tomographic scan. Thereafter, the finite element mesh is generated from this geometry. Analytical and statistical micromechanics equations are then used to calculate effective input material properties for the yarn and resin regions within the FE mesh. These analytical expressions account for the effect of resin volume fraction within the yarn (due to infiltration during curing) as well as the presence of voids within the composite. The unit cell model is then used to evaluate the effective properties of the composite.