Recent developments in the aeroelasticity of morphing aircraft

A dynamic constitutive model for fiber-reinforced composite under impact loading

A class of computationally-efficient tools to undertake progressive failure and damage analysis of composites across scales is presented. The framework is based on a class of refined onedimensional (1D) theories referred to as the Carrera Unified Formulation (CUF), a generalized hierarchical formulation that generates a class of refined structural theories through variable kinematic description. 1D CUF models can provide accurate 3D-like stress fields at a reduced computational cost, e.g., approximately one to two orders of magnitude of degrees of freedom less as compared to standard 3D brick elements. The effectiveness of 1D CUF models to undertake physically nonlinear simulation is demonstrated through a class of problems with varying constitutive models. The virtual testing platform consists of a variety of computational tools such as failure index evaluations using component-wise modeling approaches (CUF-CW), CUF-CW micromechanics, concurrent multiscale framework, interface, and impact modeling. Failure index evaluation of a class of composite structures underlines the paramount importance of the accurate stress resolutions. Within the micromechanical framework, the Component-Wise approach (CW) is utilized to represent various components of the RVE. The crack band theory is implemented to capture the damage propagation within the constituents of composite materials and the pre-peak nonlinearity within the matrix constituents is modeled using the J2 von-Mises theory. A novel concurrent multiscale framework is developed for nonlinear analysis of fiber-reinforced composites. The two-scale framework consists of a macro-scale model to describe the structural level components, e.g, open-hole specimens, coupons, using CUF-LW models and a sub-scale micro-structural model encompassed with a representative volume element (RVE). The two scales are interfaced through the exchange of strain, stress and stiffness tensors at every integration point in the macro-scale model. Explicit finite element computations at the lower scale are efficiently handled by the CUF-CW micromechanics tool. The macro tangent computation based on perturbation method which leads to meliorated performances. A novel numerical framework to simulate progressive delamination in laminated structures based on component-wise models is presented. A class of higher-order cohesive elements along with a mixed-mode cohesive constitutive law are integrated within the CUF-CW framework to simulate interfacial cohesive mechanics between various components of the structure. A global dissipation energy-based arc -length method to trace the complex equilibrium path exhibited by delamination problem. The capabitlies of

Computationally-efficient multiscale models for progressive failure and damage analysis of composites

This paper presents numerical results concerning the nonlinear and failure analysis of fiber-reinforced composites. The micromechanical framework exploits a class of refined 1D models based on the Carrera Unified Formulation (CUF) having a variable kinematic description. The recently developed CUF micromechanics is a framework for the nonlinear modeling and exploits the ability of the CUF to predict accurate 3D stress fields with reduced computational overheads. The present formulation features the von Mises J\textsubscript{2} theory for the pre-peak nonlinearity observed in matrix constituents, and the crack-band theory to capture the damage progression. Numerical examples and comparisons with results from literature assess the accuracy and efficiency of the proposed framework. The paper highlights the applicability of CUF models as an efficient micromechanical platform for nonlinear and progressive failure analysis for fiber-reinforced composites with potentially major advantages in the perspective of multiscale modeling.

Elastoplastic and progressive failure analysis of fiber-reinforced composites via an efficient nonlinear microscale model

Unsteady Aerodynamic Calculations for General Configurations by the Double-Point Method

The nonlinearity of fibre-reinforced polymer (FRP) composites have significant effects on the analysis of composite structures. This article proposes a phenomenological intralaminar plasticity model to represent the nonlinearity of FRP composite materials. Based on the model presented by Ladeveze et al., the plastic potential and hardening functions are improved to give a more rational description of phenomenological nonlinearity behavior. A four-parameter hardening model is built to capture important features of the hardening curve and consequently gives the good matching of the experiments. Within the frame of plasticity theory, the detailed constitutive model, the numerical algorithm and the derivation of the tangent stiffness matrix are presented in this study to improve model robustness. This phenomenological model achieved excellent agreement between the experimental and simulation results in element scale respectively for glass fibre-reinforced polymer (GFRP) and carbon fibre-reinforced polymer (CFRP). Moreover, the model is capable of simulating the nonlinear phenomenon of laminates, and good agreement is achieved in nearly all cases.

https://iopscience.iop.org/article/10.1088/1757-899X/87/1/012071/pdf

A phenomenological intra-laminar plasticity model for FRP composite materials

To investigate the transient aeroelastic responses of a folding wing during morphing motion, a time-varying aeroelastic equation in state space is presented. The structural model is established based on the component modal synthesis method. A time-dependent transformation is introduced to establish the compatibility equations. The aerodynamic force is obtained by double lattice method, and then the rational function fitting method is adopted to deduce the approximate expressions of the aerodynamic force in time domain which is used in conjunction with the structural model. The equations of motion in state space are solved using the Runge-Kutta numerical integration technique to predict the transient aeroelastic responses. The effects of the flow velocity and the morphing velocity are studied to deeply understand the aeroelastic characteristics of a folding wing. The numerical results indicate that the aerodynamic force contributes to the morphing motion. With a greater flow velocity or a slower morphing motion, the reaction moment will decrease. So a better aeroelastic performance can been obtained.

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Chi Hou

Papers

A phenomenological intra-laminar plasticity model for FRP composite materials

Transient Aeroelastic Responses of Folding Wing in Morphing Motion