Significance of Defects in CFRP Bonded Honeycomb Structures and Non-Destructive Test Methods for Their Destruction.

摘要

Carbon Fibre Reinforced Plastic (CFRP) skinned aluminium honeycomb sandwich materials are becoming well established in the aerospace industry. These materials exhibit high specific strength and high specific stiffness. The types of structure for which they are suitable are those which require a large stiffness to mass ratio such as side-walls, solar arrays, antenna dishes etc. Whilst a great deal is known about the behaviour of these materials there are certain areas where neither theoretical nor physical studies have so far been successfully undertaken. One of these is the problem of defects within the material and their effect on its properties. Lack of this information hampers the spacecraft designer in making a reasonable estimate of the practical properties of the materials at his disposal with the consequent risk of structural over-design. A study has been undertaken at Fulmer Research Institute in conjunction with ESTFC to identify the defects that occur in CFRP/Al sandwich materials and to assess the significance of these defects in terms of overall mechanical properties. A range of defects have been considered and all have been shown to have significant effects on laminate strength. Available non-destructive test methods have been reviewed and evaluated using specimens containing deliberately introduced defects. It has been recommended that the optimum NDT practice which is presently available involves a combination of visual examination, roller probe coupled ultrasonics and X-radiography. The performance of other techniques including holographic interferometry, laser speckle pattern interferometry and thermography is discussed. (MM).