The introduction of composite materials onto air vehicles has complicated the traditional hole/countersink assessment criteria due its finished-part thickness variability; softer and dissimilar properties than the metallic substructure where it is mounted and attached; and the increased attention to other acceptance criteria such as fiber tear, fiber pull, and moisture propagation in the hole that degrades fastener capability. The addition of composite materials further complicates the assembly process by adding a boundary layer of liquid shim or sealant between the composite piece (usually a skin) and the substructure.
Current hole inspection systems are absent the ability to assess the interior condition of the composite hole such as fiber tear, damage to the liquid shim, and debris or burrs between the multiple stacks of dissimilar material.
This paper will describe, illustrate, and define new non-contact laser inspection methods for assessing the acceptability of countersinks and holes in aerospace parts made from composite materials. The diagnostic system(s) can satisfy the full range of hole and countersink criteria and provide an evaluation of the composite material and liquid shim condition simultaneously; while collecting data to populate a knowledge base to facilitate advanced analytics.