Determination of the mixed mode stress intensity factor on weakened planes for centrally cracked polycarbonate
Abstract
The dynamic behavior of materials has been of interest for over a century. The development of high impact technology has seen great interest recently with notable fields such as weaponry, aerospace, automotive, and geoscience. There is a significant need to understand high impact on weakened plane materials. This need has greatly increased due to the advances in both manufacturing and geotechnical material response. On the manufacturing side, advances in 3D printing has lead to greater use and a broader application base. However, weakened planes are formed when subsequent layering of old and new layers are placed. Additionally, composite materials have a inherent weakened planes between fiber and matrix. On the geotechnical side, shale is critical in the extraction of oil and natural gas. In order to extract petroleum, shale must be broken to allow flow which is complicated by foliation. The influences of this fracture can be attributed to stress wave interactions across the weakened planes. However, in spite of its many applications, stress wave interactions along weakened planes has not been fully explained. This research aims to explain mixed mode fracture interactions along weakened planes by means of stress wave propagation. This is achieved by the use of a rectangular specimen that is through cut and glued back together with a central starter crack left to initiate fracture caused by a split-Hopkinson pressure bar (SHPB) and recorded using two high speed cameras. Digital Image Correlation (DIC) is used to measure both farfield, and nearfield crack tip opening displacement (CTOD) data while strain gauges on a SHPB use voltage generated from the pulse wave, is utilized to gain fracture toughness values. The stress wave propagation is broken into elastic, shear, and fracture regions and a fracture envelope is created for angles of 15° 30°, 45° and 60°. A 75° angle was attempted but was outside of the fracture envelope.
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- OSU Theses [15752]