Development of portable impact testing machine for creating low velocity impacts in composite material at arbitrary angle and position

Low-velocity impact testing plays a critical role in evaluating the damage resistance of composite laminates. However, most commercially available impact testing systems, such as vertical drop-weight towers, are bulky, laboratory-bound, and limited to vertically downward impact configurations. As a result, these systems cannot realistically reproduce oblique or combined-angle impact events that frequently occur under real service conditions, nor can they be used directly on full-scale structures. The present work addresses these limitations by introducing a portable and angle-adjustable low-velocity impact testing device capable of characterizing the impact response of composite specimens as well as imparting controlled impacts directly on composite structures. The system employs a spring-based energy storage mechanism with stepper-motor-controlled compression, infrared sensors for accurate velocity measurement, and a solenoid-based rebound catcher to prevent multiple impacts. The performance of the developed machine was experimentally validated using carbon/glass fiber reinforced polymer specimens manufactured through vacuum assisted resin transfer molding. Initially, normal impact responses were benchmarked against an INSTRON CEAST 9340 drop-weight impact tester to verify accuracy. Subsequently, the developed system was utilized to conduct normal and oblique impact tests by rotating the sample plate (max. 30°) or the complete impactor assembly (-90°-90°) about a defined axis. The experimental results demonstrate precise and repeatable energy delivery across different spring compression levels and reveal a noticeable reduction in peak force and absorbed energy under oblique impact conditions compared to normal impacts. Overall, the proposed impact testing system is highly suitable for both laboratory studies and in situ composite structures.