Microstructural damage from bullet impacts in heritage sandstones

Campbell, Oliver; Blenkinsop, Tom; Gilbert, Oscar; Mol, Lisa; Lee, Tung Lik

Abstract

Despite protection in international law, cultural heritage still suffers both intentional and inadvertent damage during conflict. Behind visible surface cratering, typically caused by small arms projectiles, is a network of microscale damage that is currently undetectable by contemporary in situ, non-destructive techniques. To this end, sedimentary stone types, analogous in strength and porosity to those used in heritage across the Middle East and North Africa, were shot with common ammunition types (7.62 x 39 mm) at 200 m to simulate current conflicts. Optical thin sections, scanning electron microscopy and neutron diffraction techniques were applied to investigate the microstructural damage. A change in deformation mechanisms with distance from the impact sees a zone of compression and shear fracturing become a region of fractures preferentially following grain-matrix boundaries. Calculation of the Young’s Moduli from neutron diffraction data shows a stiffer elastic response of samples proximal to the impact. These results are contrary to the conventional mechanisms previously reported for the influence of damage on mineral elastic properties. This study forms the basis of future works into the internal deformation mechanisms of stone at the microscale, and informs in situ studies of stone decay.

• Presentation Conference Type: Conference Paper (published)
• Conference Name: 14th International Congress on the Deterioration and Conservation of Stone (STONE 2020)
• Start Date: Sep 7, 2020
• End Date: Sep 12, 2020
• Acceptance Date: Jul 27, 2020
• Publication Date: Jul 27, 2020
• Deposit Date: Apr 21, 2022
• Pages: 993-998
• Book Title: Monument Future - Decay and Conservation of Stone. Proceedings of the 14th International Congress on the Deterioration and Conservation of Stone
• ISBN: 9783963111723
• Public URL: https://uwe-repository.worktribe.com/output/9378418
• Additional Information: Nb. in-person conference cancelled due to Covid-19. Contributions distributed in hard-copy to all authors. Volume is available to purchase online.