The Laser Bond Inspection (LBI) method is based upon stresswave dynamics in bonded materials. LBI uses a pulsed laser system to generate a compressive stress wave on the material surface. The stresswave propagates through the material, and is reflected off the back free surface as a tensile wave. The reflected tensile wave passes through the bondline and stresses the adhesive bond at a selected strength value. The figure below shows a time-lapse simulation of the stresswave propagation.
How is the Stresswave Magnitude Determined for each Inspection?
Each Laser Bond Inspection is calibrated to individual structure configuations. A series of evaluations determine the laser fluence threshold at which the bond line is dissociated based on structural geometry and material composition. The magnitude of each stresswave is specifically tailored by controlling the energy and duration of the laser pulse. Once the laser fluence threshold has been determined, the stresswave is selected to provide approximately 80% of the threshold value required for bond dissociation. This test fluence value can be customized depending upon the desired minimum strength threshold for a safe structure, and the test is configured to demonstrate that acceptable bonds meet that standard.
LSP Technologies has predictive modeling capabilities for determining threshold values and stresswave magnitudes on different structures.
How Does LBI Ensure Structures Are Safe?
Laser Bond Inspection provides proof test validation that structures meet their strength ratings and design requirements. The process is calibrated to identify weak bonds, while leaving acceptable bonds unaffected. Laser Bond Inspection does not induce any deficiencies in structures that have been assembled to acceptable specifications. If the bond passes inspection, the structure is safe to use. Even after multiple inspections in the same location, LBI does no harm to acceptable bonds.