Kazushi Haruna

Strength prediction of adhesively bonded carbon/epoxy joints

A finite element approach has been used to obtain the stress distribution in some adhesive joints. In the past, a strength prediction method has not been established. Therefore in this study, a strength prediction method for adhesive joints has been examined. First, the critical stress distribution of single-lap adhesive joints, with six different adherend thicknesses, was examined to obtain the failure criteria. It was thought that the point stress criterion, which has been previously used for an FRP tensile specimen with a hole, was effective. The proposed method using the point stress criterion was applied to adhesive joints, such as single-lap joints with short non-lap lengths and bending specimens of single-lap joints. Good agreement was obtained between the predicted and experimental joint strengths.

A study on UV‐curable adhesive sealant for LCD panel

With a view to suppressing the overlap shift between the TFT substrate and the color filter substrate, application of UV sealant is considered in the LCD panel assembly process. The initial tensile strength and moisture resistance of the UV sealant are evaluated and studied. In regard to the initial tensile strength, the stress applied to the sealing part during the glass cutting process, in which the peeling of the seal is most likely, is quantized by a numerical method based on the finite element method. By comparison of this result with tensile intensity tests of the UV sealant, acceptable performance is confirmed. The resistance to moisture is degraded due to large distortions on the interface between the sealant and the glass substrate, since a UV sealant hardened only by UV light has a large shrinkage on solidifying. Such shrinkage is small in a UV sealant that is hardened completely by applying heat after illumination of UV light, and hence presents practically no problem, with a moisture resistance equal to that in conventional heat curing-type sealant. From these results, the UV sealant completely hardened by applying heat after UV light illumination is found to be applicable to TFT-LCD from the point of view of tensile strength and humidity resistance.

Mechanical Behavior of CFRP Adhesive Joints with Thin Adherends.

Recently, adherend thickness has tended to decrease to lighten the adhesive composite structures. In this study, the mechanical behavior of CFRP adhesive joints was examined in the case in which a thin adherend was used. AE measurement and FEM analysis were performed. The adhesive-strength evaluation method that used the stress singularity parameter was applied to FEM results. Initial failure strength, which was an important factor applying the cyclic load, could be found by AE results. It was clarified that the initial failure strength decreased when thin adherend was used. According to FEM analysis, the initial failure strength could be evaluated by the intensity of the stress singularity. It was clarified that the initial failure strength decreased, since the intensity of the stress singularity at the adhesive edge increased when adherend thickness decreased, and that intensity increased, since the tensile deformation gap between the adherends became widened.