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AbstractIn this article, we organize a stretchable-thickness model to present a frequency analysis for a composite plate applicable in badminton court which is reinforced with origami graphene. A higher order kinematic model is extended in this work including three bending, shear, and stretching functions, where the stretching functions is responsible for satisfying the out of plane shear strains and stresses at top/bottom surfaces of the badminton equipment. The sport or composites plate is manufactured from a copper matrix reinforced with graphene origami where the effective material properties are calculated based on micromechanical models as a function of volume fraction and folding degree of graphene origami, material properties of matrix and reinforcement and temperature. The numerical results are presented with changes of volume fraction, folding degree of reinforcement, and thermal loading along the thickness direction. The main novelty of this work is accounting thickness stretching deformation for the analysis of a graphene origami reinforced plate and investigating the responses of graphene origami as a new reinforcement. A verification investigation is presented for approve of the methodology, and solution procedure. An investigation on the order of deformation is presented for various thickness ratio of the badminton sport plate. [ABSTRACT FROM AUTHOR]

AbstractThis paper studies the free vibration and harmonic response of Functionally Graded Graphene/Epoxy composite plates, considering the First Order Shear Deformation Plate Theory. The weight fraction of graphene variation along the thickness direction with graphene homogeneous dispersed in a polymer matrix. The effective Young Modulus of the plate is predicted by a new micro-mechanical model. The model includes the aspect ratio and weight fraction of nanoplatelets embedded into the matrix. The modal and harmonic of Graphene/Epoxy plates are obtained by the Boundary Element Method formulation for composite plates. The Young modulus calculated from the proposed micro-mechanical model highly agrees with those obtained from experimental results reported in the literature. Results demonstrate a high correlation of the micromechanical model with experimental results and other analytical models. Graphene weight fraction and ratio aspect increase the effective Young modulus of the composite. Boundary Element results show high agreement with Finite Element solutions. Numerical results for modal and harmonic analysis show concentrating graphene near the top and bottom surfaces of the plate is the most effective way to reinforce the plate for increased natural frequencies. The results demonstrate the BEM formulation and micromechanical model can be used as reliable engineering tools for the vibrational analysis of functionally grade graphene composite plates. [ABSTRACT FROM AUTHOR]

This paper presents a constitutive model for the behavior of steel fiber reinforced concrete (SFRC) under mixed mode cracking taking into account the fiber orientation effect by using a micromechanical approach. Firstly, the resistant mechanisms of an inclined fiber are modeled by a closed-form analytical function. The bridging force is calculated by integrating on the cracked surface, the product of the fiber extraction force by its orientation probability. A modified model of the aggregate interlock mechanism is combined with the fiber bridging stresses to obtain the cohesive stresses. This mesoscale model is then extended using an elastic damage model and a fixed smeared cracking concept to assess the structural behavior. The model is finally implemented in a Finite Element Analysis (FEA) software, its performance is tested with some experimental results collected in the literature. The model successfully integrates the fiber orientation effect and shows a good prediction of stress transmission. [ABSTRACT FROM AUTHOR]

Photopolymerization, based on light-induced radical polymerization, is nowadays exploited in additive manufacturing (AM) technologies enabling to achieve high dimensional quality. The mechanical properties of the obtained material are heavily dependent on the chemistry of the photopolymer and on the way the AM process is performed. Here we study, through experiments and theoretical modeling, how the mechanical properties of liquid crystal shutter (LCD) printed photopolymers depend on the printing process setup, namely UV exposure time and layer thickness. To this end, a multi-physics simulation tool considering the light diffusion, chemical kinetics, and the micro-mechanics at the network level, has been developed. [ABSTRACT FROM AUTHOR]

This study is aimed at investigating short- and long-term aged properties of glass fibre (GF)-reinforced asphalt mixtures using indirect tensile strength (ITS) and associated fracture energy, moisture susceptibility, creep compliance, resilient modulus, and indirect tension continuous and discontinuous (IDT) fatigue tests. Also, to portray the influence of fibre reinforcement at micro level, a micromechanical finite element model (MFEM) was built utilising representative volume element (RVE) to consider the effect of fibre dose, length, and dispersion (fully aligned or random) on the mechanical characteristics (or stress-strain curve) of the composite under unidirectional strain perturbation. Based on the study results, for the same binder, compared to shorter fibre (i.e. 6-mm length), the application of 12-mm GF to the mixtures showed unnoticeable change in the short- and long-term properties of the reinforced mixtures. On the whole, the GF can impart positive characteristics to the asphalt mixture such as increase strength, resistance to rutting, less susceptibility to moisture damage, retard fatigue cracking, enhance healing capability, and combat adverse aging changes. Unlike the effect of fibre length, the numerical model proved that the orientation and concentration of GF showed noticeable influence on the mechanical response of the composite. Overall, using the GF in asphalt mixtures can help produce durable bituminous pavements. Although the present study investigated the GF-reinforced bituminous materials from performance stand point, one can speculate that building GF-reinforced pavements is more costly initially compared to unreinforced pavements however the benefits may be received over time by extending service life and saving the maintenance cost of the bituminous pavement. [ABSTRACT FROM AUTHOR]

A distinct perspective of using the hybrid composite patches with varying stiffness for repair of a cracked Al 6061-T6 plate and its influence on repair performance is presented. The hybrid composite patches of carbon and glass fibers are considered. The volume fraction of constituents is selected in accordance with the required stiffness ratio. Numerical analysis is performed to evaluate the J-Integral, reduction factor of SIF and interfacial stresses. Patch hybridization has restricted the J-Integral and shown positive impact on interfacial stresses at the edges. The obtained results indicate that the hybrid composite patches have ensured alternative and effective repair solution. [ABSTRACT FROM AUTHOR]

This paper presents a micromechanical model to develop digital microstructures of asphalt mastics and crumb rubber-modified binders. The micromechanical model was based on the dissipative particle dynamics (DPD) model that is typically used for modelling suspensions. This paper utilises X-ray tomography images of particles to create microstructures. First, a database of 3D images of crumb rubber particles were generated by scanning specimens using X-ray computed tomography and X-ray microtomography. Once the 3D images were generated for individual particle shapes, a series of spherical harmonic (SH) functions were fitted to the surface of the particles and SH coefficients were determined. Utilisation of SH coefficients for each particle (rather than the actual 3D image voxels) allowed efficient numerical DPD simulations performed to generate microstructures. Example simulations were performed to generate microstructures and used to generate finite element meshes and exported to ABAQUS. The linear viscoelastic responses of the microstructures were simulated using ABAQUS and compared to the measured values. [ABSTRACT FROM AUTHOR]

In this article, the nonlinear vibration frequencies of functionally graded carbon nanotube-reinforced composite doubly curved shell panels under elevated thermal environment are numerically investigated using finite element method. The doubly curved carbon nanotube-reinforced shell panel has been modeled mathematically using higher-order kinematics theory and Green–Lagrange geometrical nonlinear strains. The properties of the individual constituents of the graded composite are assumed to be temperature dependent. In addition, the properties of the media are obtained based on the modified rule of mixture. The carbon nanotubes are dispersed nonuniformly through the thickness direction. The large deformation kinematic effects on the structural responses are counted by including all the nonlinear higher-order terms in the formulation. The desired nonlinear responses are computed numerically using our in-house computer code in conjunction with the direct iterative scheme. The convergence and the accuracy of the present numerical model have been checked by solving various numerical examples. Nonlinear mechanical responses were affected by several other design parameters and explored numerically for the thickness ratios, volume fractions, temperature loading, type of geometries, and type of grading under the uniform thermal environment. [ABSTRACT FROM AUTHOR]

The present article investigates the analytical and computational derivation of the moduli of continuous fiber-reinforced composites. Theoretical expressions for the longitudinal and transverse elastic moduli and also for the longitudinal and transverse Poisson ratios, which were derived taking into account the concept of boundary interphase between fibers and matrix, were obtained as a function of the fiber volume fraction. The micro-scale model considers that the composite material consists of three phases: the fiber, the matrix, and the interphase. The latter is the part of the polymer matrix lying at a close vicinity to the fiber surface. In this investigation, it was assumed that the interphase is inhomogeneous in nature with varying mechanical properties. Different laws of variation of its elastic modulus and Poisson ratio were taken into account in order to define the overall modulus of the composite. Thermal analysis method had been used for the estimation of the thickness of the interphase. An investigation about the influence of an interphase region on the elastic constants given by the rules of the mixtures is also carried out. Finite element analysis was performed in order to obtain the elastic constants and to compare them with the respective theoretical values derived from the interphase model and with those from other models and also with experimental results. [ABSTRACT FROM AUTHOR]

This work aims mainly to derive closed-form expressions for the effective properties of layered composites when linear uncoupled and coupled phenomena, such as conduction, elasticity, thermoelectricity and piezomagnetoelectricity, are concerned. In addition, properties may be graded in the direction normal to the layer plane. The remarkable feature of the obtained results is that they are expressed in a unified and very compact way for all uncoupled and coupled linear mechanical and physical phenomena. Our results include as special ones all the relevant results reported up to now in the literature. The key to obtaining our general compact coordinate-free results resides in extending Hill’s interfacial relations for a perfect elastic interface to the setting of an arbitrary finite number of uncoupled and coupled linear phenomena. The effects of the presence of stiffeners and softeners on the effective properties of layered composites are also investigated. In particular, four limiting cases for piezoelectricity are studied in detail. As illustrations, the general results are applied to several coupled phenomena and to functionally graded layered composites. [ABSTRACT FROM PUBLISHER]

In this study, an idealised asphalt mixture was modelled with the discrete element method for both two-dimensional (2D) and three-dimensional (3D) cases. The air voids were randomly generated and counted within the models to reach a specific air void level (e.g. 6%). The 2D models were used to compute the strain and stress responses when the specimens were subjected to a compressive load. Then, the moduli of the specimens were computed from the stress-strain curves. The 3D idealised model was generated using a number of layered 2D models. The air void distribution patterns were also studied with 2D and 3D randomly generated models at specific air void levels. The results showed that the modulus deviation increases when the air void level increases. In addition, the modulus deviations of the 3D models were found to be much lower than those of the 2D models. When comparing the modulus predictions from the 2D models with those from the 3D models, the research proved that the 3D models yielded higher moduli than the 2D models. The average of the predicted modulus difference between 2D and 3D models was 26% at 10% air voids, and 7% at 4% air voids. When the air void increased from 0 to 10%, the modulus decreased by 30% in the 3D models, when compared with 48% in the 2D models. The 2D and 3D models predicted the same modulus for 0% of air voids. However, the 2D models under-predicted the mixture modulus, especially when the air void level was higher. In the 2D modelling of the asphalt mixtures, a large number of models were needed to achieve a reasonable prediction due to larger deviation, even at lower air void levels. At higher air void levels, the 3D models yielded a much higher prediction than 2D simulations. [ABSTRACT FROM AUTHOR]

An attempt has been made to model the plane-strain fracture toughness, KIc, in Al-Zn-Mg-Cu alloy forgings subjected to overageing. The proposed model, based on the multiple micromechanisms, reveals the quantitative relations between fracture toughness, fraction of all fracture modes and microstructural parameters associated with multiscale-sized second-phase particles and precipitate-free zones. The new model is validated by the present quantitative data of microstructural and fractographic analysis performed along with mechanical tests on hot-forged plates in T73 condition. The relevant parameters changed by the compositional variations were determined in two orientations. It was found that the predicted KIc values represent the tendency of fracture toughness change well. The new model provides better agreement for the case of dominant transgranular fracture mode. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effect of the volume fraction of zalacca fibres on the tensile strength and modulus of the LDPE-ZF composites both experimentally and analytically. The tensile tests were carried out on the randomly oriented LDPE-ZF composites manufactured by hot-pressing method. Hirsch and Bowyer-Bader's model was used to predict the tensile strength of the composites where the elastic modulus was determined by using Tsai-Pagano, Manera and Cox-Krenchel's model. The experimental results of tensile strength and elastic modulus of the composites was close by the Bowyer-Bader and Tsai-Pagano's model, respectively. It is due to the consideration of fibre length and orientation factor in the Bowyer-Bader's model and fibre elastic anisotropy in the Tsai-Pagano's model. This study establishes that the hot press method is applicable for processing LDPE-ZF composites [ABSTRACT FROM AUTHOR]