Dynamic Mode II Fracture Response of PMMA Within an Aquatic Environment

Abstract

Sheets of Poly Methyl Methacrylate (PMMA) 3 mm thick are lasercut into rectangles, and then subjected to a high-energy impact while submerged in distilled water, to investigate the effect that submersion may have on mode II fracture. The experiment has been carried out using a compressed air gun, which launches a delrin projectile towards the PMMA test specimen. A unique apparatus was constructed, which contains and allows the test specimen to be suspended in distilled water, while the projectile impacts a buffer adhered to the test specimen. The buffer transfers the impact onto the edge of the test specimen. Transparent walls in the apparatus allow the use of ultra-high-speed photography (up to 10Mfps), and digital image correlation (DIC) to measure dynamic response within the specimen throughout fracture. Data collected was used to calculate critical stress intensity factor. Results are compared to those from experiments in which test samples are not submerged.