하성규 교수

A finite element formulation is presented for modeling the dynamic as well as static response of laminated composites containing distributed piezoelectric ceramics subjected to both mechanical and electrical loadings. The formulation was derived from the variational principle with consideration for both the total potential energy of the structures and the electrical potential energy of the piezoceramics. An eight-node three-dimensional composite brick element was implemented for the analysis, an

The micromechanics of failure was developed to predict the failure of continuous fiber reinforced composites. A micromechanical approach using unit cells of square and hexagonal arrays was employed to compute the micro stresses of constituents and at the fiber—matrix interface, which were used to determine the failure initiation of a unidirectional ply. The constituent properties include two tensile and compressive strengths of fiber and matrix, plus normal and shear strengths at the interface.

Nowadays, the rapid climate change, water pollution and harmful gas emissions are largely caused by the extensive use of petrochemicals and the burning of plastic materials. The government authorities across the globe and experts mentioned that the dumping of plastic waste and non-biodegradable materials is a principal problem of the environmental pollution. In their numerous chemical forms, cellulose and various other biodegradable materials can be possible alternatives to resolve these challen

A three-dimensional finite element (FE) model for the multi-level lower cervical spinal segment C3-C6 has been developed using computed tomography (CT) data, and applied to study of the effects of the fusion and the artificial disc prosthesis on the biomechanical behavior of the lower cervical spine. The NURBS computer adided dedsig (CAD) data used in this study for modeling the vertebrae facilitate adding surface patch layouts for seamless attachment of the soft tissues, such as intervertebral

The most practical way of storing hydrogen gas for fuel cell vehicles is to use a composite overwrapped pressure vessel. Depending on the driving distance range and power requirement of the vehicles, there can be various operational pressure and volume capacity of the tanks, ranging from passenger vehicles to heavy-duty trucks. The current commercial hydrogen storage method for vehicles involves storing compressed hydrogen gas in high-pressure tanks at pressures of 700 bar for passenger vehicles

Hydrogen fuel cell technology is securing a place in the future of advanced mobility and the energy revolution, as engineers explore multiple paths in the quest for decarbonization. The feasibility of hydrogen-based fuel cell vehicles particularly relies on the development of safe, lightweight and cost-competitive solutions for hydrogen storage. After the demonstration of hundreds of prototype vehicles, today, commercial hydrogen tanks are in the first stages of market introduction, adopting con

A three-dimensional micromechanics of failure model was developed and applied in order to predict triaxial failure envelopes and stress–strain curves for 12 test cases in the Second World-Wide Failure Exercise (WWFE-II), which involves five continuous fiber–matrix laminates and multi-axial loadings, including those in through-thickness direction. The micromechanics of failure is based on micromechanical unit cell models, which characterize the microstructure of composites, and consists of indepe

In this paper, the strength of braided textile composites is predicted using a multi-scale approach bridging the mesoscale and microscale regimes. Mesoscale finite element models of representative unit cells of biaxial and triaxial braided composites are developed for predicting strength. The constituent stresses of tows inside the braided unit cell are calculated using micromechanics. Correlations between mesoscale stresses and microscale constituent stresses are established by using stress amp

An eight-port impedance matrix and an equivalent circuit are presented for the analysis of an asymmetric triple-layered piezoelectric bimorph with separate electrical ports. The separate electric ports for the top and bottom piezoelectric layers operate independently of each other: they generate and/or sense the coupled extensional and flexural motions. Taking into account shear and rotatory inertia, the eight-port impedance model is first obtained for the bimorph. The electromechanical behavior

A micromechanics-based constituent progressive damage model was proposed in this study to predict macroscopic failure behavior of composite laminates under multi-axial mechanical loadings as well as thermal influences. For this purpose, a micromechanics-based failure theory, named the micromechanics of failure, has been further developed not only to account for the constituent failure but also to progress damage. We first modeled the unit cell of the microstructure of a UD lamina both to derive