Keiichi Shirasu

Abstract Epoxy‐amine thermosetting resins undergo different reactions depending on the amine/epoxy stoichiometric ratio ( r ). Although many desirable properties can be achieved by varying the stoichiometric ratio, the effects of the variation on the crosslinked structure and mechanical properties and the contribution of these factors to the ductility of materials have not been fully elucidated. This study investigates the brittle‐ductile behavior of epoxies with various stoichiometric ratios an

The mechanisms underlying the influence of the surface chemistry of inorganic materials on polymer structures and fracture behaviours near adhesive interfaces are not fully understood. This study demonstrates the first clear and direct evidence that molecular surface segregation and cross-linking of epoxy resin are driven by intermolecular forces at the inorganic surfaces alone, which can be linked directly to adhesive failure mechanisms. We prepare adhesive interfaces between epoxy resin and si

To enable the development of multiwalled carbon nanotubes (MWCNTs) with superior mechanical properties, a theoretical model of the tensile strength of MWCNTs is developed, and the structural–mechanical property relationships of MWCNTs are investigated using experimental results obtained by uniaxial tensile tests from this study and data from the literature. We show that the nominal tensile strength is an important design factor in determining the mechanical properties of composites reinforced wi

The stress-strain responses and damage initiation/propagation mechanisms of T700G/LM-PAEK, an open-hole carbon-fiber-reinforced thermoplastic were investigated experimentally and numerically. To obtain the mechanical properties necessary for numerical simulations, uniaxial tensile/compressive, double cantilever beam, and end notched flexure tests were conducted. T700G/LM-PAEK was found to have comparable or higher Young’s modulus, strength, and interlaminar fracture toughness relative to thermos

To apply carbon nanotubes (CNTs) as reinforcing agents in next-generation composites, it is essential to improve their nominal strength. However, since it is difficult to completely remove the defects, the synthesis guideline for improving nominal strength is still unclear, i.e., the effective strength and the number of nanotube layers required to improve the nominal strength has been undermined. In this study, molecular dynamics simulations were used to elucidate the effects of vacancies on the

In this study, the nominal tensile strength, Young's modulus and Weibull scale and shape parameter of the nominal tensile strength distribution of the MWCNTs synthesized by a thermal chemical vapor deposition (CVD) method were investigated by conducting uniaxial tensile tests. In addition, the structural defects which induced the failure of the MWCNTs were observed by a transmission electron microscope (TEM). TEM observations revealed that the MWCNTs exhibited several types of structural defects

Thermoplastic carbon fiber-reinforced plastics (CFRPs) are increasingly utilized in the aerospace industry owing to their beneficial properties and enhanced formability relative to thermoset CFRPs. Despite the extensive use of these materials, studies focusing on compression after impact (CAI) tests with impact energies exceeding 20 J for thermoplastic CFRPs remain scarce. This study examines CAI tests on quasi-isotropic laminates of thermoplastic CFRP, subjected to a low-velocity impact energy

With the expansion of use of carbon fiber reinforced plastics (CFRPs), it becomes important to obtain precise knowledge of elastic properties carbon fibers in radial direction as well as axial direction. Although the elastic property in radial direction of polyacrylonitrile (PAN)-based carbon fibers have been investigated using ultrasound scatter measurements, compression tests of single fibers and nanoindentation, there is no experimental evaluation for the pitch-based carbon fibers which posse