木材‐エポキシ樹脂接着体のへき開疲労強度

Abstract

Cleavage fatigue tests were carried out on double cantilever type specimens bonded with epoxy resin adhesives containing different amount of flexibilizer (polysulfide). Fatigue strength (σ7) was compared with static strength (σ0), and the effect of flexibility and thickness of glue-line on the fatigue properties of the bond system were discussed.The results obtained were summarized as follows:(1) The cleavage fatigue strength decreased with increasing flexibility of glue-line, while the static strength of the same type specimens increased effectively with it.(2) Both the fatigue and static strengths increased with increasing glue-line thickness, and the effect in the latter was greater than that in the former.(3) The fatigue strength (σ7) of all bonded specimens was lower than that of solid wood specimens, while the specimens bonded with epoxy resin containing 40 or 60phr flexibilizer exceeded the solid wood specimens in static strength.(4) Contrast in fatigue and static properties of bonded specimens in relation to thickness and flexibility of the glue-line could be explained with the complex effects of relaxation of stress concentration at the fracture point with increasing thickness and flexibility of the glue-line (plus effect) and decrease of cohesion of the adhesive polymer with increasing flexibilizer mixed (minus effect).