Ballistic impact studies of a borosilicate glass

L.C. Forde , W.G. Proud , S.M. Walley , P.D. Church , I.G. Cullis

The ballistic impact properties of a borosilicate ('pyrex') glass was studied using mild steel rods accelerated using a light gas gun. High-speed photography at sub-microsecond framing rates was used along with schlieren optics to investigate the propagation of elastic shock waves and fracture fronts. Flash X-radiography was used to visualize the deformation of rods as they penetrated the comminuted glass normally. The rod was seen initially to dwell on the surface for at least 3μs creating a Hertzian cone-crack. Later on, between 40 and 60μs, self-sharpening of the projectile was observed as the 'wings' of the heavily deformed front end sheared off. After this event, the front of the rod speeded up. X-rays also showed that the pattern of fissures within the comminuted glass was observed to be very similar shot-to-shot. X-radiography was also used to examine the mechanisms occurring during oblique impact of rods at 45°. In oblique impact, bending of the rod rather than plastic deformation ('mushrooming') takes on the role of distributing the load over an area larger than that of the original rod diameter. High-speed photography of the rear surface of a glass block on which a fine grid had been placed confirmed that the comminuted glass moved as larger interlocked blocks. The experiments were modelled using the QinetiQ Eulerian hydrocode GRIM making use of the Goldthorpe fracture model. The model was found to predict well the transition from dwell to penetration.

Mots clés: ballistic impact; borosilicate glass; X-radiography; high-speed photography; fine grid technique; Goldthorpe fracture model; hydrocode modelling; schlieren

Domaines: Physique [physics]

L.C. Forde, W.G. Proud, S.M. Walley, P.D. Church, I.G. Cullis. Ballistic impact studies of a borosilicate glass. International Journal of Impact Engineering, 2010, 37 (5), pp.568. ⟨10.1016/j.ijimpeng.2009.10.005⟩. ⟨hal-00665445⟩