Non-destructive examination of adhesive bonds with neutron radiography

The neutron radiography method has been applied in the non-destructive examination of aluminium single lap specimens bonded with an epoxy (Met1bond-1113). The resolution was good. All of the bonding flaws visible on the radiographs were easily detectable on the approx. 0.152mm thick adhesive post-fracture surfaces. The direct exposure method used is described. The stress/strain behaviour of five aluminium/Met1bond specimens containing inherent flaws of various sizes is shown. The wide variation indicates the need for a testing method so that the joints with flaws can be discarded or allowance made for the strength reduction caused by the flaws. Neutron radiography is shown to be a suitable technique. (U.K.)