Akira Udagawa

Molecular motion of several epoxy resins and influence of electron irradiation

Abstract Electron irradiation effects on the molecular motion of epoxy resins and a composite reinforced by carbon fibre were studied. The materials used were three epoxy resins that were cured by diaminodiphenylmethane: diglycidyl ether of bisphenol A (DGEBA), diglycidyl ether of bisphenol F (DGEBF) and tetraglycidyl diaminodiphenylmethane (TGDDM); and carbon-fibre-reinforced TGDDM/diaminodiphenylsulphone. A mechanical loss peak appeared for all epoxy resins in the temperature range from 50 to 100°C. The results of heat treatments indicated that this relaxation is related to the local motion of chains subjected to an internal stress produced during curing. The internal stress was more marked for the tetrafunctional epoxy (TGDDM) than for the difunctional ones (DGEBA and DGEBF). The main reaction induced by irradiation is chain scission, and the order of radiation resistance of the epoxide monomers was revealed to be TGDDM > DGEBF > DGEBA.

Radiation processing for carbon fiber-reinforced polytetrafluoroethylene composite materials

Abstract The present work is an attempt to evaluate the performance of the fiber composites with crosslinked polytetrafluoroethylene (PTFE) as a polymer matrix by radiation. The uni-directional carbon fiber-reinforced composites were fabricated with PTFE fine powder impregnation method and then crosslinked by electron beams irradiation under selective conditions. The carbon fiber-reinforced crosslinked PTFE composites show good mechanical properties compared with crosslinked PTFE. The radiation resistance of crosslinked PTFE composites is improved more than that of crosslinked resin without fiber.

Electron irradiation effects on interlaminar shear strength of glass or carbon cloth reinforced epoxy composites

Interlaminar tensile shear tests are conducted to study the degradation mechanisms of electron irradiated glass or carbon cloth reinforced epoxy laminates. Interlaminar shear strength decreases significantly after the dose exceeds 3000 Mrad for glass/epoxy, but remains constant up to 12 000 Mrad for carbon/epoxy. SEM photos reveal that debonding of glass fibres and epoxy matrix (or degradation of silane coupling agents) plays an important role in the dose-dependent strength reduction of glass/epoxy laminates. The decrease in the interlaminar shear strength corresponds to that in the three-point bending strength. On the other hand, the SEM fracture appearance is almost dose-independent for carbon/epoxy laminates. In addition, some preliminary irradiation tests are conducted at −120° C to observe the effects of irradiation temperatures.

Application of radiation-crosslinked polytetrafluoroethylene to fiber-reinforced composite materials

Abstract Plain-woven carbon fiber-filled polytetrafluoroethylene (PTFE) composites were fabricated by radiation-crosslinking under selective conditions. High mechanical and frictional properties are found in the composite materials compared with crosslinked PTFE without fiber. The composite materials with optional shapes, which are laminated after electron beam (EB) crosslinking treatment of each mono-layer could also be fabricated.

Radiation induced debonding of matrix-filler interface in organic composite materials

Mecanisme de degradation radiochimique de stratifies resine epoxyde ou polyimide tissus de verre

Preparation and radiation-resistance evaluation of glass fibre composites having various epoxy matrices

Influence de la composition et de la formulation de la resine sur la resistance au rayonnement

Degradation behavior of fiber reinforced composites under irradiation by 3 MeV electrons

Abstract Mechanical properties of fiber reinforced plastic composite laminates (plain woven fiber, glass or carbon; matrix, epoxy or polyimide resin) were measured by a three-point flexural test and interlaminar tensile shear test after irradiation with 3 MeV electrons at room temperature. Fracture surfaces were observed by means of scanning electron microscopy after each mechanical test. Radiation resistance and degradation behavior varied depending on the relative radiation stability of the matrix and the interface between the fiber and matrix. When the matrix was less stable, the laminates degraded with rapid decomposition of the matrix. On the other hand, the degradation proceeded with debonding at the fiber-matrix interface when the matrix was stable. Treatment of the interface with some aromatic silane compounds was found to be effective in enhancing the radiation resistance of glass-cloth reinforced laminates.

Influence of Fiber upon the Radiation Degradation of Fiber-Reinforced Plastics.

繊維強化プラスチックの放射線劣化に及ぼす繊維の影響を, 2MeVの電子線を用いて調べた. 耐放射線性は, 母材にビスフェノールA系エポキシを用いた積層板の三点曲げ強度から評価した. カーボン繊維積層板はガラス繊維積層板より, かなり高い耐放射線性を示した. カーボン繊維とガラス繊維充填材の間にある違いを調べるため, 母材としてポリエチレンを用いてモデル化した積層板の吸収線量とゲル分率の関係を調べた. ゲルの生成はカーボン繊維を充填した場合に著しく遅かった. この結果からカーボン繊維には母材樹脂に対する放射線保護作用があり, これが炭素繊維強化プラスチックに高い耐放射線性を与える主な原因となっていることが分かった.

Radiation effects on flexural strength and mode-I interlaminar fracture toughness of conventional and toughened epoxy matrix CFRP

For CFRP used as structural materials in space, the flexural strength and mode-I interlaminar fracture toughness (GIc) at high, room and low temperatures, and the effect of irradiation were studied. Conventional and toughened carbon fiber reinforced plastic (CFRP) kept high flexural strength even at 120 MGy. For conventional CFRP, GIc was improved by irradiation, and it kept good properties at 60 MGy. For toughened CFRP, apparent GIc was really high because fibers bridge between the beams. The fracture modes in the three point bending test and the fracture surfaces of DCB specimens were observed to study the fracture mechanisms.

Degradation Behaviour of Fiber Reinforced Plastic under Electron Beam Irradiation

Various mechanical properties of four kinds of glass fiber-reinforced plasrics irradiated with electron beams were examined at three temperatures; room temperature, 123 K and 77 K. Dynamic viscoelastic properties were measured, and fractography by means of scanning electron microscopy was observed in order to clarify degradation behaviour. A considerable decrease in interlaminar shear strength (ILSS) at room temperature was observed above 60 MGy. On the other hand, the three-point bending strength at 77 K and the ILSS at 123 K decreased with increasing irradiation. Fractography reveals that the degradation of the interface layer between matrix resin and fiber plays an important role in the strength reduction at 123 K and 77 K. These findings suggest that the interface between matrix resin and fiber loses its bondability at 123 K arid 77 K after electron beam irradiation.