Flash X-ray cinematography analysis of dwell and penetration of smallcaliber projectiles with three types of SiC ceramics

In order to improve the performance of ceramic composite armor it is essential to know the mechanisms during each phase of the projectile–target interaction and their influence on the penetration resistance.Since the view on the crater zone and the tip of a projectile penetrating a ceramic is rapidly getting obscured by damaged material,a flash X-ray technique has to be applied in order to visualize projectile penetration.For this purpose,usually several flash X-ray tubes are arranged around the target and the radiographs are recorded on film.At EMI a flash X-ray imaging method has been developed,which provides up to eight flash radiographs in one experiment.A multi-anode 450 k V flash X-ray tube is utilized with this method.The radiation transmitted through the target is then detected on a fluorescent screen.The fluorescent screen converts the radiograph into an image in the visible wavelength range,which is photographed by means of a high-speed camera.This technique has been applied to visualize and analyze the penetration of 7.62 mm AP projectiles into three different types of Si C ceramics.Two commercial Si C grades and MICASIC(Metal Infiltrated Carbon derived Si C),a C-Si Si C ceramic developed by DLR,have been studied.The influences,not only of the ceramic but also the backing material,on dwell time and projectile erosion have been studied.Penetration curves have been determined and their relevance to the ballistic resistance is discussed.

Damage visualization and deformation measurement in glass laminates during projectile penetration

Transparent armor consists of glass-polymer laminates in most cases.The formation and propagation of damage in the different glass layers has a strong influence on the ballistic resistance of such laminates.In order to clarify(he course of events during projectile penetration,an experimental technique was developed,which allows visualizing the onset and propagation of damage in each single layer of the laminate.A telecentric objective lens was used together with a microsecond video camera that allows recording 100 frames at a maximum rate of 1 MHz in a backlit photography set-up.With this technique,the damage evolution could be visualized in glass laminates consisting of four glass layers with lateral dimensions 500 mm x 500 mm.Damage evolution was recorded during penetration of 7.62 mm AP projectiles with tungsten carbide core and a total mass of 1 1.1 g in the impact velocity range from 800 to 880 m/s.In order to measure the deformation of single glass plates within the laminates,a piece of reflecting tape was attached to the corresponding glass plate,and photonic Doppler velocimetry(PDV) was applied.With the photonic Doppler velocimeter.an infrared laser is used to illuminate an object to be measured and the Doppler-shifted light is superimposed to a reference light beam at the detector.The simultaneous visualization and PDV measurement of the glass deformation allow determining the deformation at the time of the onset of fracture.The analysis of the experimental data was supported by numerical simulations,using the AUTODYN commercial hydro-code.