* Corresponding author. Tel.: 00-1-604-822-2800; fax: 00-1-604-822-6901. E-mail address: reza.vaziri@ubc.ca (R. Vaziri) International Journal of Impact Engineering 24 (2000) 155}170 An e$cient method for continuous measurement of projectile motion in ballistic impact experiments Darlene Starratt, Tim Sanders, Elvis Cepus \ , Anoush Poursartip, Reza Vaziri* Composites Group, Departments of Metals and Materials Engineering and Civil Engineering, The University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada Received 9 June 1998; received in revised form 15 July 1999; accepted 26 July 1999 Abstract This paper provides a description of a simple and cost-e!ective continuous measurement system for impact. Originally developed at Johns Hopkins university for use in #yer plate impact experiments, the measurement system has been enhanced for the continuous, non-contact measurement of projectile displace- ment during ballistic impact events. A sheet of laser light is progressively blocked and unblocked by the projectile, and the corresponding change in total intensity is measured and converted to a displacement}time curve. Through the use of simple mathematical operations, the system can be used to determine the time histories of projectile velocity and acceleration, impact force and projectile energy loss during an impact event. While this technique can be applied to a wide range of engineering materials, this paper presents examples of measurement results for impact of composite and textile targets.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Continuous measurement; Ballistic impact; Composite materials 1. Introduction The use of advanced composite materials in applications involving impact by foreign objects has been steadily increasing. The velocities involved with these types of impact event cover a wide range. Low-velocity impacts, on the order of 1 m/s, represent a tool being dropped on a composite structure. Intermediate velocities, in the range of 10}100 m/s, represent runway debris striking an airplane. Ballistic (high velocity) impacts, in the velocity range of 100}1000 m/s, represent the 0734-743X/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 0 7 3 4 - 7 4 3 X ( 9 9 ) 0 0 0 4 5 - 7