The mechanical properties of composites increased by an incorporation of fiber/particle. When the stress was applied to the composite, the stress was transferred to the crystalline regions of incorporated fiber/particle through matrix and interface. In this study, "X-ray diffraction method" was applied to investigate the stress transfer system in the composite (fiber reinforced composite, such as high performance polyethylene/epoxy resin, carbon fiber/epoxy resin, cellulose fiber/poly-L-lactic acid, and particulated composite such as crystalline silica/epoxy resin, montmollironite/polyvinyl alcohol) from a microscopic point of view. Here, the stress ratio (stress applied to the composite/ stress on the reinforcement) is defined as stress concentration factor x, then the x value is show to change from 0.5 to more than 60 depending on a variety of parameters, such as reinforcement/matrix combination, anisotropy of the reinforcement, adhesion at the interface, particle size, content, fatigue and so on. The reinforcement formula using this x value is proposed, where the increase of the macroscopic Young's modulus with the incorporation of the particle could be explained quantitatively. We also found the x value more than the unity indicates that stress was concentrated on the fiber/particle, which is considered to bring about the mechanical reinforcement of the composite. The "X-ray diffraction method" proved to be quite powerful method for detecting the stress transfer of the composite in situ and non-destructively.

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Multi-layered laminates composed of two polyethylene (PE)-glycidyl methacrylate copolymers sheets and an inserted polypropylene (PP) sheet were fabricated, and the peel adhesive strengths of the laminates were evaluated. The surfaces of PP sheet were pre-treated by O2-plasma to make reactive groups on the surfaces. The relation between the amount of reactive groups and the peel adhesive strength was evaluated. Also, the mechanisms of peel adhesive strengths were discussed using scanning electron microscopy of the fracture surfaces. The interfacial adhesion of PE/PP was improved with the amount of the reactive groups. As the results, the dilatational plastic deformation including cavitation occurred in the PE layer at the vicinity of the interface of PE/PP, where mechanical constraint would be strong. The plastic deformation of the bulk PE layer by the improvement of the interfacial adhesion is responsible for the energy absorption, which resulted in the increased peel adhesive strengths.

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The apparatus which can observe the top and side views of stringiness behavior of pressure-sensitive adhesive (PSA) was prepared. The stringiness behavior of the acrylic PSA was observed with wide range of peeling load for some adherends having different critical surface tension (γc).The peel rate of each peeling can be measured using the apparatus. The peeling load for the peeling rate of 0.02 mm/s was measured for each PSA, and the value was showed as "Load (0.02)". That is, the peeling rate obtained by the constant load peeling measurement is able to be converted into the peeling load having the same unit as the adhesion force by this method. The Load (0.02) increased with the γc of adherend, however the contribution of γc to the Load (0.02) was found to be very low. On the other hand, the good correlation was obtained between the Load (0.02) and the width of saw-teeth shaped stringiness (R2 = 0.89) .It was found that the shape of stringiness is strongly dependent on the interfacial adhesion force and the mechanical properties of the PSA, the base material of tape and the adherend. And the interfacial adhesion force is affected by the wettability of PSA and adherend (γc), and the surface morphologies of PSA and adherend. Although the γc is a major factor, it is not all.

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