CONTENTS

Flexible adhesives are visco-elastic materials. Therefore, creep will occur under any load. The challenge for the engineer is to design the bonded structure to restrict creep to acceptable levels. Finite Element Analysis can be used to predict the creep behaviour of adhesive joints under load. Time-dependent property measurements-creep compliance or stress relaxation- are required for accurate predictions These measurements can be made in tension using bulk test specimens. However, such measurements can be difficult to perform and analyse accurately. Modern oscillatory rheometers have been shown to have the capability for performing time-dependent property measurements on flexible adhesives. Stress relaxation methods are likely to give more reliable time-dependent properties for FEA of flexible adhesives than creep measurements. This is because it is easier, in relaxation measurements, to identify and separate the ‘elastic ’ response from the time-dependent response. However, relaxation measurements will not yield information on failure whereas creep measurements can