Hitoshi Kodama

Evaluation of the fatigue strength of adhesively bonded CFRP/metal single and single-step double-lap joints

Abstract Generally, the adhesive layer of an adhesively bonded joint is under a state of concentrated multiaxial stress. Hence, stress multiaxiality and concentrated stress distributions must be taken into account in estimating the strength of adhesive joints. In our previous study [1] , a fatigue-failure criterion was investigated which took account of the stress multiaxiality in adhesively bonded CFRP/aluminum butt, scarf and thick-adherend lap-shear joints, which have uniform stress distributions in the adhesive layer. Another parameter governing the strength characteristics of the adhesive joints is the concentrated stress distribution due to the stress singularity at the corners of the adhesive/adherend interface. Recently, stress-singularity parameters have been used to evaluate the strength of adhesive joints. However, there are few studies evaluating the fatigue strength from this point of view. In this study, a method of estimating the fatigue strengths of adhesively bonded single-lap, cracked single-lap and single-step double-lap joints composed of CFRP and an aluminum alloy is proposed which is based on two stress-singularity parameters.

Fatigue failure criterion of adhesively bonded CFRP/metal joints under multiaxial stress conditions

Abstract In order to investigate the fatigue failure criterion of adhesively bonded CFRP/metal joints under multiaxial stress conditions, a series of fatigue tests was carried out on three kinds of adhesively bonded joint specimens; butt joint, scarf joint and thick-adherend lap-shear joint, where these joints have considerably uniform stress distributions in the adhesive layer. In addition, stress distributions of these joints were analysed by the finite element method. The results show that the fatigue limits of respective joints are governed by the maximum principal stress except when negative hydrostatic pressure acts on the adhesive.

Development of non-joint-moulding-technique on huge mast for Nippon Challenge America's Cup Boat

The Americas Cup which is a worldwide and traditional yacht race was held in San Diego, USA in 1992. Japans Nippon Challenge Americas Cup team participated in this race for the first time. Big yachts with 34 meter masts competed in match races, and the Japanese team although a newcomer, gained an excellent result. The masts properties being lightweight and having good balance contributed much to the victories. In the early stages we thought manufacturing a 34 meter long huge CFRP mast without jointing was a dream: however, this dream turned out to be real. We present a report on the non-joint moulding technique of this huge primary structural CFRP mast which was developed for the first time in Japan.