The effect of ionomer thickness on mode Ⅱ interlaminar fracture toughness was investigated for ionomer - interleaved CF / epoxy laminates. Laminates were fabricated with Toho UT500 / 111 prepregs. Ethylene based ionomer, which forms the toughened interphase at the ionomer / base lamina interfaces, was used as an interleaf material. Thickness of ionomer film was selected as 25,100 and 200 μm. Mode Ⅱ fracture toughness tests were carried out using end notched flexure specimens. Fracture toughness values were much improved by interleaving the ionomer films. The fracture toughness values increased linearly with increasing the ionomer thickness. This thickness effect of the ionomer interleaf differs from that under mode I loading where the presence of ionomer is more effective than the increase in its thickness. Microscopic observation revealed that the main crack path was inside the toughened interphase and at its interfaces. Plastic deformation of the ionomer expanded through the whole ionomer region in the thickness direction. Difference in the thickness effect on fracture toughness between under mode I and Ⅱ loadings were discussed from the view point of the size of the plastically deformed region.

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The effect of a surface treatment of glass beads with a silane coupling agent on a yield stress was investigated in the beads - filled poly (vinyl chloride) as typical ductile polymer matrix. γ - Aminopropyl methyldiethoxysilane was used as silane. The amount of silane necessary for creating monolayer coverage was calculated. The beads were treated with the silane in the range from 0.5 to 10 times of the amount necessary for monolayer coverage in water by some different conditions. The treated beads were washed with methanol to remove the unfixed silanes on the surfaces. The fixing ratio of the silane was determined by a carbon analysis of the treated beads both for as treated and methanol washed. A comparison between the yield stresses of the resins filled with both as treated and methanol washed beads was made. As a result, the yield stress increased with increasing the amount of silane treated in the range below that for monolayer coverage. However, a further improvement on the yield stress was not obtained in the range above the amount. The unfixed silanes on the bead surface depressed the improvement on the yield stress.

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In order to improve the toughness of silica filled acrylic composite, two typical impact modifiers, multi-layer core/shell particle and polymerisable elastomer, were examined. The IZOD impact strength of the composite was not affected by the core/shell particle, while significant improvement was observed in the elastomer modification. The difference was detected at the fracture surface by scanning electron microscope (SEM) observation and elemental analysis which was given by energy-dispersed X-ray micro-analyzer equipped with the SEM (SEM-EDX) . The result suggested that the curable elastomer transferred the destruction phase from silica/matrix interface to inside of the matrix. The major contribution of the elastomer for this transfer was thought to be adhesion promotion at silica/PMMA interface, while the core/shell particle toughened the matrix only. Consequently, the elastomer modified acrylic composite was toughened farther by core/shell particle very efficiently, because the destruction occurred in the toughened matrix phase. The concept for toughening in silica filled acrylic composite was provided through this work, and the effective toughening method was proposed.

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This study dealt with thermal stresses and delamination growth in scarf joints under uniform temperature change by photoelastic measurement and a two-dimensional finite elementan alysis. The adherends were aluminum plates and an adhesive layer was modeled and manufactured from an epoxide resin plate. Adherends and epoxide resin plate were bonded using a heat setting and one component type adhesive. The adhesive was cured at high temperature and cooled to room temperature. The thermal stress was then generated in the scarf joint during temperature change and measured by the photoelastic experiments. After that the scarf joints were cooled stepwise, delamination growth from the edge of the interface was measured. It was confirmed that the delamination initiated from the edge of the interface was not the obtuse angle side, but the acute angle side. When the scarf angle was 90 degree, i.e., in adhesive butt joints, the resistance against the delamination was minimum. The thermal stresses in the scarf joints with thin adhesive layer were also analyzed. It was expected that the thermal strength increased with a decrease of an adhesive layer thickness. The stress singularity near the edge of the interface was calculated from the stress distributions in the joints with different scarf angles. As a result, the stress singularity in the scarf joints under thermal loads was quite different with that under mechanical tensile loads.

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