TWI Industrial Member Report Summary 706/2000
C I C Manger and G Thomas
Composite materials offer significant benefits over conventional engineering materials, including higher specific strength and stiffness and increased corrosion resistance. However, these advantages are often compromised at joints, due to poor or over-conservative design. Also, material removal and fibre damage in mechanically fastened joints, and poor surface preparation and debonding in adhesively bonded joints can compromise their performance. Industrial usage of composite materials remains below potential, which, in part, can be attributed to a lack of design and reliability data for joints.
A critical factor in the design and application of composite structures is therefore an understanding of the joining methods and their performance in service. The service life of joints is dependent, not only upon their design, but also on their response to flaws and damage, which may be introduced during manufacture and/or service. Consequently, an understanding of the damage tolerance characteristics of joints and techniques available to improve resistance to flaw growth while retaining structural integrity is essential to the successful application of composites.
This report looks at the current understanding of damage tolerance in composite structures and joints. Initially, aspects of the properties, applications and fracture of composites are reported. The report then concentrates on joints in composites, discussing typical flaws and failure modes, design methodologies and predictive methods for the failure of joints with and without flaws.
- To identify industries possessing an active interest in composite-composite joining, and to define materials of significant interest for further evaluation.
- To review typical flaws and failure modes in composite materials and joints in composite structures.
- To review design tools available for improving the resistance to damage of joints in composite structures.
- To identify current techniques for modelling the failure of composite-composite joints.
- To establish the current position of damage tolerance analysis tools for composite-composite joints.
- To identify areas for investigation for the experimental programme of the current Core Research Project.