Yoshiaki Kawagoe

Gas flow in porous media can be seen in various engineering devices such as catalytic converters and fuel cells. It is important to understand transport phenomena in porous media for improvement of the performance of such devices. Porous media with pores as small as the mean free path of gas molecules are used in such devices as proton exchange membrane fuel cells. It is difficult to measure molecular transport through such small pores in the experimental approach. In addition, even when using t

Multiscale modeling, comprising quantum-chemical reaction path calculation, curing molecular dynamics (MD) simulation, microscopic finite-element analysis (FEA), and macroscopic FEA, was developed to predict the manufacturing-process-induced deformation of carbon-fiber-reinforced plastic (CFRP) laminates. In this approach, the thermomechanical properties, volumetric shrinkage due to the curing reaction, and gelation point of the matrix thermoset resin were evaluated using MD simulations coupled

A material with anisotropic heat conduction characteristics, which is determined by molecular scale structure, provides a way of controlling heat flow in nanoscale spaces. As such, here, we consider layer-by-layer (LbL) membranes, which are an electrostatic assembly of polyelectrolyte multilayers and are expected to have different heat conduction characteristics between cross-plane and in-plane directions. We constructed models of a poly(acrylic acid)/polyethylenimine (PAA/PEI) LbL membrane sand

We performed non-equilibrium molecular dynamics (NEMD) simulations on bulk amorphous polyacrylic acid (PAA) with three polymer chain lengths to investigate molecular mechanism of thermal energy transfer in heat conduction. Thermal conductivity obtained by NEMD simulations increased as the polymer chain length of PAA increased, and its dependence on polymer chain length exhibited a saturation behavior. By decomposing heat flux into each contribution of molecular interactions, it was found that do

This study experimentally and numerically investigated the mechanisms of process-induced deformations (PIDs) and subsequent long-term deformations (LTDs) in thermosetting CF/epoxy (T700G/2510) and thermoplastic CF/PAEK (T700G/LM-PAEK) aerospace-grade prepreg laminates. Warpage deformations in asymmetric cross-ply laminates after autoclave fabrication were measured over 84 days under controlled conditions (60 °C and 50%RH). A finite element analysis integrating anisotropic viscoelastic constituti

The effectiveness of multiscale modeling, consisting of quantum chemical reaction path calculations, molecular dynamics simulations, and microscopic and macroscopic finite element analysis, developed for the process-induced residual deformation of carbon fiber-reinforced plastic was experimentally evaluated. In this study, non-crimp fabric composites with an arbitrary thermoset resin were fabricated, and process-induced deformation was measured. Process-induced residual deformations due to cure

A multiscale model is developed to comprehensively predict the failure parameters associated with the elasto-plasticity of a unidirectional carbon-fiber-reinforced composite lamina; the prediction is performed according to the resin-matrix design. The developed model involves quantum-chemical reaction-path calculations, molecular-dynamics simulations, and micromechanical analyses at the filament scale. The presented model is further combined with an advanced numerical approach developed based on

Deformation analyses of polymeric materials using molecular dynamics (MD) simulations are very useful in evaluating the physical properties based on the atomic features. Generally, the average responses of a system, such as the stress–strain response, are evaluated, but a molecular chain around a solid should deform in an unusual manner in a composite system, such as a solid/polymer system. This may lead to damage and a microscopic inelastic deformation, ultimately affecting the macroscopic beha

Reaction-induced phase separation occurs during the curing reaction when a thermoplastic resin is dissolved in a thermoset resin, which enables toughening of the thermoset resin. As resin properties vary significantly depending on the morphology of the phase-separated structure, controlling the morphology formation is of critical importance. Reaction-induced phase separation is a phenomenon that ranges from the chemical reaction scale to the mesoscale dynamics of polymer molecules. In this study

Thermal oxidative degradation behaviors of epoxy resin cured with cyanate ester and conventional amine are experimentally evaluated in terms of heat resistance and flame retardancy, and the degradation mechanisms are further investigated using ReaxFF molecular dynamics simulations. Thermogravimetric analysis revealed that both resins exhibit multi-step decomposition behavior, with the cyanate-cured resin showing nearly double the residual weight (char formation) compared to the amine-cured resin

Global air passenger transport demand is expected to increase, and there is concern that the current airport operation will not be able to cope with aircraft overcrowding. In this study, we developed a cellular automaton simulator that can model the surface traffic of the entire Tokyo International Airport in detail, including aircraft that are arriving, taxiing, parking, and departing, using actual track data. The simulator can reproduce stop-and-go aircraft taxiing based on aircraft interactio

Epoxy resin has been extensively used in the field of advanced electronic materials as an adhesive and encapsulant owing to its excellent material properties. However, recently, there has been a demand for further improvement in heat resistance, high transparency, environmental resistance, and enhanced handling properties for high-brightness light-emitting diodes. Conventional aromatic epoxy resins lack light resistance; therefore, a colorless and transparent epoxy resin without aromatic rings i