SBIR-STTR Award

In order to simulate the high velocity involved in ballistic impacts, at least up to some extent, laboratory used gas guns have been developed for material and structure testing. However, if the projectiles of the guns are not instrumented, they cannot provide information concerning impact mechanisms and damage processes during impacts. In an effort to improve their measuring capability, accelerometers may be added to the gun projectiles. Besides, due to the small dimensions, large deformation and high frequency involved in ballistic impacts, difficulties in extracting impact mechanisms and damage processes will continue to exist. Strain gage based high-velocity ballistic impactors are very different from strain gage based low-velocity drop-weight impactors. The former are based on strain wave propagation while the latter deformation. Many more challenges are expected to encounter in the development of high-velocity instrumented ballistic impactors than that in the low-velocity drop-weight impactors. However, the reward of an instrumented ballistic impactor will be enormous. It can help to improve the understanding of the impact mechanisms involved in ballistic impacts and the damage processes occurred in the impacted specimens. Hence, the design of composite materials and structures for combating ballistic impacts can be greatly accelerated.

Keywords:
Ballistic Impact, Instrumented Projectile, Fiber Composite Materials And Structures, Impact Mechanisms, Damage Processes

Due to the complex wave propagation and vibration involved in dynamic loading, commonly used sensors, such as electrical resistance strain gauge and accelerometer, cannot adequately measure the true loading history without a specially designed mechanism. In the Phase I study, an innovative mechanism was successfully designed, constructed and proved to be able to recover the strain wave history caused by ballistic impact. A microprocessor was also designed and built for recording and processing the strain wave signals. Combining the innovative wave recovering mechanism and the microprocessor with a battery and a protection gear, an instrumented projectile was completed. In order to validate the accuracy of the instrumented projectile, a special facility was also designed and constructed. Experimental studies successfully demonstrated the capability and accuracy of the instrumented projectile in recording impact-induced force histories. In the Phase II study, it is required to refine the instrumented projectile for more advanced applications. For example, instrumented projectiles with smaller diameter and higher impact velocity are necessary to simulate the harsh environments encountered by the small arm projectiles used in military?s operations. In order to meet these requirements, additional considerations, such as wireless transmission and non-stand-alone designs will also be explored.

Keywords:
Ballistic Impact, Instrumented Projectile, Composites, Impact Mechanisms, Damage Processes