A novel method to detect crack location and volume in opaque and semi-opaque brittle materials

Abstract

This research is an investigation into the use of liquid core hollow glass capillary fibers for the potential detection of cracking in opaque and semi-opaque brittle materials. The study was originally intended to combine work based on the concept of internal adhesive delivery from hollow fibers for repair with nondestructive analysis of crack location and cracking volume within the same system; however the detection system is the topic of this paper. The liquid filled hollow fibers can carry light. A cracked capillary tube which has released some liquid projects a diffraction pattern from the meniscus at the ends of the adhesive. The size relationship of these meniscuses allows us to predict the location of the fiber crack and the volume of the liquid lost into the matrix. For example, in the case of a standard capillary pipette with one-half of its liquid lost from one end, the two meniscuses projected circles approximately 4 and 2 mm in diameter. If the same amount of liquid is lost not from one end, but from somewhere else along the length of the pipette, the two to one relationship in size will remain, but the actual size will vary with distance of the meniscuses from the projection screen. The clarity of these relationships should allow later prediction of matrix crack location and volume.