Jin-Ho Noh

The thermal post-buckling responses of shape memory alloy hybrid composite (SMAHC) shell panels are investigated using a finite element method formulated on the basis of the layerwise theory. The von Karman nonlinear displacement–strain relationships are applied to consider large deflections due to thermal loads. The cylindrical arc-length method is used to take account of the snapping phenomenon which is an unstable behavior observed in the shell panels. A nonlinear finite element procedure bas

In this research, the thermomechanical responses of shape memory alloy (SMA) actuators and their applications in the shape adaptive structures combining strip SMA actuators are investigated. The numerical algorithm of the three-dimensional (3-D) SMA thermomechanical constitutive equations based on Lagoudas model is developed to analyze the unique characteristics of a SMA strip. The Green–Lagrange strain-displacement relationships are adopted to consider the large displacements, large strains, an

To characterize the nonlinear relationship between load and displacement and its dependency on temperature and time variations, the rate form of thermomechanical constitutive equations for shape memory polymers is newly derived. Experimental tests of the shape memory polymers are analyzed to acquire the parameters needed for the model. In order to generate a fast recovery rate and a higher recovery ratio, an asymmetric shape memory polymer composite reinforced with woven fabrics is developed and

Abstract The methodology to adaptively change the configuration of an airfoil using a shape memory alloy (SMA) thin film actuator to improve aerodynamic performance is numerically demonstrated. To predict the thermomechanical behaviors of an SMA thin film, a 2-D incremental formulation of the SMA constitutive model is developed. By implementing a numerical algorithm of the SMA thin film, the interactions between the airfoil structure and SMA thin film actuator are investigated. Airfoils with eit

Abstract The thermal post-buckling and vibration characteristics of composite conical shells are investigated using a finite element method. Based on the layerwise theory and the von Karman displacement strain relationships, the nonlinear finite element equations of motion are derived for the thermoelastic response of the composite conical shell structure. The cylindrical arc-length method is used to account for the snapping phenomenon. The influence of the structural parameters, such as the sem

The loading‐rate dependency on the pseudoelastic behaviors of shape memory alloy (SMA) wires is experimentally and numerically investigated. The results are analyzed to estimate the parameters for a thermomechanical constitutive model of SMA wire with strain‐rate dependency of the hysteresis behavior. An analytical model of SMAs is developed by using nonconstant parameters during various strain rates. Numerical simulations are performed to demonstrate the accuracy of the improved model.

The interactions between the inflatable structure and shape memory alloy (SMA) strip actuators are investigated using finite element simulation. The numerical algorithm of the 3-D SMA thermomechanical constitutive equations based on Lagoudas model is implemented to analyze the unique characteristics of SMA strip. For the numerical results presented in this paper, the ABAQUS finite element program has been utilized with an appropriate user supplied subroutine (UMAT) for the modeling SMA strip. In

This article investigates (experimentally and numerically) the time and temperature-dependent folding and unfolding behavior, including the structural nonlinearity, of thin-walled softenable composite structures. The composites are fabricated with woven fabric fibers and a heat softenable material of the shape memory polymer (SMP) resin. A numerical model is developed. The model is based on the elastic properties of the woven fabric fibers, their fabric geometry, and the thermo-viscoelastic prop

Poisson's ratio, ν, was measured for four materials, a rubbery polymer, a conventional soft foam, and two auxetic foams. We find that for the first two materials, having ν ≥ 0.2, the experimental determinations of Poisson's ratio are in good agreement with values calculated from the shear and tensile moduli using the equations of classical elasticity. However, for the two auxetic materials (ν < 0), the equations of classical elasticity give values significantly different from the measured

A sandwiched morphing structure is developed using an Origami-inspired shape memory dual-matrix composite core and shape memory polymer composite skins. The geometric parameters of the morphing structure are designed to have a zero Poisson’s ratio. In addition, an analytical model is developed to analyze the three-dimensional morphing structure easily. The shape memory dual-matrix composites are fabricated with woven fabrics based on the shape memory polymers, and an epoxy matrix is used to ensu

Abstract Silica for epoxy molding compounds (EMCs) was coated via plasma polymerization using an RF plasma (13.56 MHz) as a function of the plasma power, gas pressure, and treatment time. The monomers utilized for the plasma polymer coatings were 1,3-diaminopropane, allylamine, pyrrole, 1,2-epoxy-5-hexene, allyl mercaptan, and allyl alcohol. The EMC samples were prepared from biphenyl epoxy resin, phenol novolac, triphenyl phosphine, and plasma polymer-coated silica, and the loading of silica wa