Laser Vibrometry for Non-Destructive Body Armor Defect Detection

Cornerstone Research Group Inc. (CRG) proposes to demonstrate the use of Laser Doppler Vibrometry as an effective method for detecting faults in ESAPI and LWP armor plates. The United States Marine Corps utilizes body armor plate systems for soldier protection in dangerous environments. It is imperative that the armor the marines are using is defect free, since a faulty plate will endanger the life of the wearer. Legacy armor systems, specifically the Enhanced Small Arms Protective Insert (ESAPI) have a well-established method for detecting faults. An x-ray machine is used to detect ceramic layer cracks, while an easy to perform ōtap testö was used to test for delaminations. However, a newer, lighter weight armor system has recently been developed, the USMC Lightweight Plate (LWP). Unfortunately, due to the difference in construction, old methods of testing do not adequately detect defects. Thus, what is needed is a new method for detecting defects in these armor systems. Laser Doppler vibrometry is a non-contact measurement technique used to quantify and analyze vibrations in various objects and structures. It involves the use of a laser beam to measure the displacement or velocity of a target's surface by detecting the Doppler shift caused by the movement. Given a standard armor configuration, the armor will vibrate with an expected vibration profile. Cracks and delaminations within the armor will cause the vibration profile to change, and therefore will be detectable. In the Phase I Base effort, CRG will demonstrate the feasibility of Body Armor Defect Detection using Laser Vibrometry. CRG will generate an expected range of vibration profiles for each armor plate. Based on the results from testing, CRG will develop an algorithm that will detect deviations from the undamaged armor profile. CRG will then fabricate a prototype test system that will securely hold the armor plates in a known position and measure them. A scanning laser doppler vibrometer (SLDV) will measure the frequency and amplitude response across the face of the armor and provide a pass / fail criterion for the armor defect detection. CRG plans to capstone the Phase I with a demonstration of the prototype testing system.