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This paper presents a numerical method for simulating the crack propagation in functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates. The numerical method is based on 2-D natural element method (NEM) which can overcome the inherent demerits of FEM and conventional meshfree methods. The 3-D displacement field of cracked orthotropic plate is formulated using the (1, 1, 0)* hierarchical model and approximated by 2-D NEM. The thickness-wise mixed-mode stress intensity factors (SIFs) are computed using the modified interaction integral I(1,2) and the 2-D complex-valued crack-tip singular fields. The crack propagation angle is determined by the modified maximum circumferential stress (MCS) criterion, and the crack trajectories are predicted by an incremental crack propagation simulation scheme. The present numerical method is verified from the comparison of predicted crack trajectories with the published reference solutions. Moreover, using the developed numerical method, the crack trajectory characteristics of FG-CNTRC plates are parametrically investigated with respect to the major parameters. From the parametric investigation, it is found that the crack trajectories of FG-CNTRC are significantly influenced by the material orientation angle and the stiffness ratio. But, the effects of the initial crack angle and the volume fraction and volume fraction pattern of CNTs are not remarkable. [ABSTRACT FROM AUTHOR]

The effect of geometrical nonlinearities due to pressure load on the thermal buckling and dynamic characteristics of composite plates are investigated in this paper, which is the main contribution of this research work. The mechanical behavior of the plate is described with the first-order shear deformation theory. The geometrical nonlinearity due to both thermal effect and pressure load is introduced in the finite element model of the plate via additional stiffness matrices. Thermal buckling and modal analysis of a four-sided simply supported rectangular composite plate under different pressure fields are conducted. Numerical results show that both the mode frequencies and critical buckling temperature of the plate rise with the increase of the pressure. The vibrational mode shapes change with the gradient pressure load field. The maximum buckled deflection point moves from the center to the place where is easier to reach compressive stress state under uniform thermal load. The pressure distribution has a significant effect on the buckling mode shapes of the plate. [ABSTRACT FROM AUTHOR]

This research paper presents an isogeometric plate finite element formulation for analysis of thick composite plates. Isogeometric finite element method which is based on non-uniform rational B-splines (NURBS) basis functions, is a novel numerical procedure developed to bridge the gap between CAD and FEM modeling of structures. In order to investigate the behavior of isogeometric plate elements under static loading, plate kinematics is based on third order shear deformation theory (TSDT) of Reddy, which is free from transverse shear locking. This paper discusses accurate transverse stress recovery procedures for TSDT isogeometric finite elements. Numerical experiments with quadratic, cubic and quartic elements are presented and obtained results are compared to other available ones. [ABSTRACT FROM AUTHOR]

A graphene-reinforced composite plate (GRCP) with a sandwich-like structure is proposed. The nonlinear mechanical characteristics of the sandwich-like GRCP are investigated and compared to those of functionally graded and uniform GRCPs. The modified Halpin-Tsai model is employed to estimate the material parameters, and the Hamilton principle is used to derive the governing equation for the composite plates. The effects of the graphene nanoplatelet (GPL) distribution patterns, weight fraction, and the number of layers on the static and dynamic nonlinear responses of the plates are investigated. The results show that the various GPL distribution patterns have different enhancement effects on plates. Compared with the graded and uniform distribution patterns, the sandwich-like distribution pattern has significant advantages in terms of anti-vibration and anti-bending properties. Furthermore, it is found that the stresses of the sandwich-like GRCPs are discontinuous, there exist stress mutation phenomena between the surface layers and the pure matrix layer. [ABSTRACT FROM AUTHOR]

The nonlinear dynamics of functionally graded graphene nanoplatelets (GPLs) reinforced composite plates are studied based on the first-order shear deformation theory (FSDT). The ordinary differential equation of the plate is derived by Hamilton principle and Galerkin method. The multi-scale method is used to analyze the jump forces. The effects of GPL distribution pattern, weight fraction, total number of layers and plate size on the resonance peak under sweep excitations, the maximal amplitude and attenuation time under impact loads, the jump force under harmonic excitations are quantitatively studied. The highest nonlinearity is found for the plate with uniform GPL distribution. The change of the number of layers has no effect on the nonlinearity but affects the natural frequency. The size of the plate and weight fraction of GPL both influence the natural frequency and nonlinearity, thereby influencing the dynamic characteristics. [ABSTRACT FROM AUTHOR]

Laminated and segmented ceramic/polyurea composite plates were fabricated by coating bulk ceramic plate and bonding ceramic tablets with polyurea, respectively. Also, nacre-like ceramic/polyurea composite plates, which mimic the "brick-mortar" structure of nacre, were fabricated by layering segmented ceramic/polyurea composite plates in a staggered way and bonding them with polyurea. Drop-weight impact tests were performed for the composite plates and corresponding bulk ceramic plates of similar size. The failure mode and low velocity impact resistance of the composite plates and the bulk ceramic plates were compared. The effects of polyurea on low velocity impact resistance of ceramic were analyzed. It is found that the laminated composite plate has much higher failure energy than the bulk ceramic plate due to the buffering effect of polyurea coating. The segmented composite plate has better multiple-impact resistance than the bulk ceramic plate, due to the crack arrest effect of polyurea filler between ceramic tablets. The nacre-like composite plate has better multiple-impact resistance compared with the bulk ceramic plate of similar thickness, since it can stop cracks propagating in plane and along thickness. [ABSTRACT FROM AUTHOR]

This work aims to explore optimal design and control of thermal buckling for composite laminates with piezoelectric fiber reinforced composite (PFRC) actuators. Four-variable trigonometric shear deformation theory without introduction of a shear correction factor is used in the structural modeling. The high accuracy of the present approach is examined by analyzing the critical buckling temperature and natural frequency compared with references results. A temperature feedback control approach is proposed in designing the controller. Taking fiber angle as the optimization design variable, layerwise optimization approach (LOA) is applied to maximize critical buckling temperature of piezolaminated plate and a set of stacking sequences are obtained. The resulting analysis demonstrates that the proposed control approach can clearly increase the critical buckling temperature of piezo-laminated plates. The optimization process developed is useful in devising stacking sequences for the piezo-laminated structures in thermal environments. [ABSTRACT FROM AUTHOR]

A simple and effective approach based on refined plate theory (RPT) is proposed to study the static and free vibration characteristics of functionally graded CNT-reinforced composite (FG-CNTRC) plates. Compared to traditional higher order shear deformation theories (HSDTs), the proposed method shows more efficient for FG-CNTRC plates analysis. To solve the C1-continuity requirement of the RPT, we used isogeometric analysis (IGA) to approximate the displacement field, which shows more advantages than the FEA, since it can construct higher-order elements without additional variables. This is an advantage for plate structural analysis because more variables make the calculation cumbersome. Finally, four types of FG-CNTRC plates were investigated and the results show the accuracy and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

E-glass/epoxy composite is very prone to small impact such as dropping tools or splash rocks, which can cause damage or degradation to E-glass/epoxy composite components. A progressive damage model for E-glass/epoxy composite in ABAQUS Explicit was developed in this study to numerically predict low-velocity impact (LVI) damage and residual strength of an E-glass/epoxy composite component. Hashin-Rotem criteria were used to define laminate damage initiation, and traction-separation law was used to define the cohesive region. LVI and four-point bending after the impact (BAI) of the woven E-glass/epoxy composite plates were simulated and compared with available experimental data in the literature. Good agreement was found between finite element analysis (FEA) predictions and the experimental results, which include the impact zone shape, as well as the load-deflection response and residual bending strength from the four-point bending tests. [ABSTRACT FROM AUTHOR]

In order to investigate both static and dynamic characteristics of composite plates and validate a contemporary, non-invasive experimental technique a comparative experimental and numerical analysis was performed. Three, geometrically the same but different in ply orientation, carbon-epoxy laminates were tested in both healthy and damaged conditions. Damages were inflicted in a shape of horizontal crack. Experiments and numerical simulations were performed by digital image correlation (DIC) and finite element method (FEM), respectively. Obtained time-responses of the tested structures were fast Fourier transformed (FFT) to frequency domain for a clearer understanding of natural frequencies and oscillation modes. Results are presented in tabular and graphical form. The overall correspondence of two sets of structural displacements is satisfactory. Some discrepancies might be contributed to the idealized geometry and restraint consideration. Also, due to the fast damping of higher tones, the errors in determining higher natural frequencies increase but still remain in 5 % range. [ABSTRACT FROM AUTHOR]

To improve the small deformation and high stress level in hinge zones of compliant mechanisms with isotropic material, a topology optimization method of compliant mechanisms with composite laminated plates was proposed. Based on the anisotropy and designability of composite laminated plates, a topology optimization model of compliant mechanisms with composite laminated plates was built to maximize the deformable capability. Numerical examples of designing compliant inverters and grippers were investigated to demonstrate the effectiveness of the proposed method. The influence mechanism of layer sequences on topologic shapes, deformation and loading capability were also discussed. The results showed that the deformable capability and stress levels of compliant mechanisms with composite laminated plates were further improved by a reasonable configuration of layer sequences. [ABSTRACT FROM AUTHOR]

Present investigation is concerned about dynamic response of composite sandwich plates with the functionally gradient foam cores under time-dependent impulse. The analysis is based on a model of the gradient sandwich plate, in which the face sheets and the core adopt the Kirchhoff theory and a {2, 1}-order theory, respectively. The material properties of the gradient foam core vary continuously along the thickness direction. The gradient plate model is validated with the finite element code ABAQUS®. And the results show that the proposed model can predict well the free vibration of composite sandwich plates with gradient foam cores. The influences of gradient foam cores on the natural frequency, deflection and energy absorbing of the sandwich plates are also investigated. [ABSTRACT FROM AUTHOR]

Finite element method based numerical simulations are performed to identify low-velocity impact-induced asymmetrically-located delamination in the [0/90] and [0/90] composite plates, respectively, using a fundamental symmetric guided wave mode (S). The wave attenuation effect due to the viscoelasticity of the composite material is modeled by calculating the Lamb wave attenuation constants and using the Rayleigh proportional damping model. The estimated sizes and locations of the delamination in both plates were in good agreement with the experimental measurements. Moreover, the analysis of wave structure of the impacted plates shows that when the S mode propagates through the damaged region, the delamination mouth opens up due to the presence of standing waves, which are generated as a consequence of multiple reflections of trapped waves with the delamination boundaries. [ABSTRACT FROM AUTHOR]

An efficient numerical algorithm for analyzing dynamic response of orthotropic viscoelastic composite laminates has been developed in the time domain. The integral form of the constitutive laws is exploited. Generalized Wiechert model is adopted to simulate the viscoelasticity of the structure Mindlin-Reissner plate theory is utilized in finite element formulation employing the consistent mass matrix. The proposed algorithm is incorporated in the framework of the finite element based on the displacement model. Newmark Constant average acceleration method is used for integration equation of motion. The developed recurrence formula permits the new time solutions to be evaluated using only previous time values. The developed solution technique is applied to orthotropic plate under two types of force, which are the step-pulse and sin-pulse force. [ABSTRACT FROM AUTHOR]