On the calculation of energy release rate in composites by Finite Elements, Boundary Elements and Analytical Methods

To characterize a transversal crack evolution in a cross-ply [0/90]s fiber reinforced composite laminate, the associated energy release rate (ERR) was calculated by means of the J-integral embedded into the finite element method (FEM). The ERR values computed for the propagation of the transversal crack were correlated to the ones obtained by using the virtual crack closure technique (VCCT) embedded within the boundary element method (BEM). In addition, the results were compared with analytical values. The results correlated well except when the crack length was approximately 80% of the ply thickness. In such case, ERR values showed some discrepancies between FEM and BEM. The reason stems from the fact that in the VCCT used not all components of the stresses are considered, resulting in smaller ERR values. In addition, the results proved that transversal cracks can influence each other only at a limited distance

Piezoelectric energy harvester composite under dynamic bending with implementation to aircraft wingbox structure

In this paper, an investigation on the energy harvesting exerted by the dynamic bending responses of a piezoelectric embedded wingbox is presented. An innovative hybrid mathematical/computational scheme is built to evaluate the energy harvested by a mechanical system. The governing voltage differential equations of the piezoelectric composite beam are coupled with the finite element method output. The scheme is able of evaluating various excitation forms including dynamic force and base excitation. Thus, it provides the capability to analyse a complicated structure with a more realistic loading scenario. Application to the simulation of a notional jet aircraft wingbox with a piezoelectric skin layer is shown in some detail. The results pointed out that the electrical power generated can be as much as 25.24 kW for a 14.5 m wingspan. The capabilities and robustness of the scheme are shown by comparison with results from the literature

A Large Strains Finite Element Multiscale Approach

A novel formulation for multiscale finite element analysis of multi-phase solids undergoing large strains is proposed in this paper. Within the described homogenization technique no constitutive assumptions are made at the macrolevel. A crucial aspects of the approach is the modelling of antiperiodic traction on the boundary of the representative volume element, condensation technique and the formulation performed on a deformation-driven context whereby the macroscopic deformation gradient is prescribed. Numerical tests on solids with voids demonstrated the robustness of the technique

Finite element analysis of the damage mechanism of 3D braided composites under high-velocity impact

The integrated near-net-shape structure of 3D braided composites provides excellent impact resistant properties over laminated composites. However, the load distribution and damage mechanism throughout the braided structures become more complicated. In this paper, a finite element model based on three unit-cells is established to assess the penetration process of 3D braided composites under high-velocity impact. A 3D rate-dependent constitutive model is employed to determine the constituent behavior in the three unit-cells. An instantaneous degradation scheme is proposed initiated by appropriate failure criteria of yarns and matrix. All these constitutive models are coded by a user-material subroutine VUMAT developed in ABAQUS/Explicit. The whole process of ballistic damage evolution of 3D braided composites is simulated, and the impact resistance and damage mechanisms are analyzed in detail in the simulation process. The effects of impact velocity on the ballistic properties and energy absorption characteristics of the composite structures are also discussed

Characterisation of creep behaviour using the power law model in copper alloy

This paper presents a numerical strategy for the characterisation of the creep behaviour model of the copper alloy, which is widely used in aircraft applications under creep conditions. The high possibility of the material failing, while operating under load at an elevated temperature, has led to the important study of the creep lifetime prediction analysis, by presenting the Norton’s rule based on the Power-law model to describe the secondary creep behaviour of the material. In order to demonstrate the nature of the creep formulation, the SOL 400 modules from MSC Nastran 2014 are implemented in order to conduct the uniaxial tensile test in 2000 N of applied load and 473 K of temperature condition. As a result, the exponential curve is formed from the relationship of the creep strain rate and stress, with a 5.1% error based on the value of the stress exponent, n, between the simulation and experimental results and this was still be acceptable because it was relatively small due to the formulation in the simulation. Consequently, a relation of the creep rate curve can then be plotted with respect to the load steps and the variation patterns due to the stress factor also being discussed. Therefore, the results show a good agreement, which indicates the capability of this model to give an accurate and precise estimation of the secondary creep behaviour of the materials

A refined sin hyperbolic shear deformation theory for sandwich FG plates by enhanced meshfree with new correlation function

The moving Kriging interpolation-based (MKI) meshfree method is extended to mechanical behavior analysis of isotropic and sandwich functionally graded material plates. The MKI meshfree method, which is free of shear correction factors effect in plate analysis, is further enhanced by introducing a new multi-quadric correlation function, eliminating drawbacks of its conventional form, gaining accurate solution. In this paper, a new refined sin hyperbolic shear deformation plate theory (N-RSHSDT) is introduced for plate kinematics. The present theory gives rise to four governing equations only, and achieves the sin hyperbolic distribution of the transverse shear strains through the plate thickness. To show the accuracy and effectiveness of the developed method, numerical experiments are performed for both isotropic and sandwich composite plates

Implementation of multiphase piezoelectric composites energy harvester on aircraft wingbox structure with fuel saving evaluation

The multiphase composite with active structural fiber (ASF) has proven able to provide better optimization between actuating and load bearing capability compared to a pure piezoelectric material. In this paper, the multiphase composite application is further extended for energy harvesting purpose. The Double-Inclusion model combined with Mori-Tanaka method is implemented in a computational code to estimate the effective electro-elastic properties of the multiphase composite. The effective composite properties obtained via the present code are in good agreement with the analytical, experimental and finite element results. The multiphase composite with different composition is applied to a typical jet aircraft wingbox with 14.5 m halfspan. The energy harvesting evaluation by means of hybrid FEM/analytical piezoelectric energy harvester model is presented. A new procedure to investigate the trade-off between the aircraft weight, the fuel saving and the energy harvested is developed. The results pointed out that the equivalent fuel saved from the power generated by the wingbox is more than enough for 1 h Auxiliary Power Unit (APU) operation

Evaluation of piezoelectric energy harvester under dynamic bending by means of hybrid mathematical/isogeometric analysis

In this paper, a novel hybrid mathematical/isogeometric analysis (IGA) scheme is implemented to evaluate the energy harvesting of the piezoelectric composite plate under dynamic bending. The NURBS-based IGA is applied to obtain the structural response exerted by the mechanical loading. The dynamic responses conveniently coupled with the governing voltage differential equations to estimate the energy harvested. The capabilities of the scheme are shown with the comparison against analytical and full electromechanical finite element results. As there is no need of fully coupled electromechanical element, the scheme provides cheaper computational cost and could be implemented with standard computational software. Thus, it gives great benefit for early design stage. Moreover, the robustness of the scheme is shown by the couple with high order IGA element which has been proven less prone to the shear locking phenomena in the literature. The computational results show greater accuracy on structural responses and energy estimation for a very thin plate compared to the couple with standard finite element method