Tensile failure mechanisms of historic fibrous plaster ceiling wads: Experiments at the UK Diamond Light Source

Abstract

Fibrous plaster (FP) ceilings, prevalent in late 19th- and early 20th-century UK theatres, are suspended using ‘wads’. Wads are hangers made of Plaster of Paris, reinforced with twisted woven jute fabric. Several recent collapses in historic fibrous plaster ceilings have been attributed to tensile failures in wads. To understand the failure mechanisms involved, tensile tests were performed on laboratory-produced wad-like samples at the I12 beamline of the UK Diamond Light Source. The tested samples were designed with a dog bone shape and mounted with clevis-grips at each end, to ensure controlled failures along the gauge length. The beamline offered the opportunity to conduct simultaneous synchrotron X-ray computed tomography (sCT) and diffraction measurements during loading, enabling the monitoring of internal crack formation and strain propagation at the microstructural scale. Simultaneously, acoustic emission (AE) and digital image correlation (DIC) measurements were conducted. Preliminary results from these datasets are discussed in this paper. The datasets will provide useful information to validate the ongoing development of algorithms which can categorise the internal failure mechanisms and damage state of wads using only AE signals.