Design requirements, particularly for lightweight structures, often dictate that adhesives must sustain and transfer loads in the structure. The performance of these joints needs to be quantitatively predicted at the design stage. The accuracy of design calculations is dependent upon the validity of the materials models used to describe the deformation behaviour of the adhesive and adherends (such as steel, aluminium, composites), and the availability of suitable materials property data for these models. As well as extensive experience in obtaining materials data for adhesives and plastics, testing of adherend materials is also undertaken.

Low stiffness or 'flexible' adhesives find many applications in joining or sealing owing to their ability to constrain differential movements of parts and their vibration damping properties. Flexible adhesives above their glass transition temperatures are characterised by low stiffness and large strains to failure. These materials appear to be best modelled by hyperelastic models developed for rubbers. There are many hyperelastic models available to the engineer. Accurate modelling of hyperelastic materials requires material properties data measured to large strains under different states of stress. Details of the data requirements for the hyperelastic materials models are available.

Rubber-toughened adhesives are ductile materials that exhibit extensive non-linear deformation before failure. It is possible to model this deformation using elastic-plastic materials models and, in conjunction with a finite element analysis, to predict stress and strain distributions in the adhesive layer in a bonded joint.

For more information, please contact Louise Crocker