Use of the tapered double-cantilever beam geometry for fracture toughness measurements and its application to the quantification of self-healing

Abstract

The successful invention of self-healing polymer composites a decade ago necessitated a methodology to quantify the ability of the material to heal and recover structural properties following damage. Healing efficiency was defined as the ratio of healed to virgin fracture toughness, η = KIChealed/ KICvirgin. Early work took advantage of the crack length independence offered by a tapered double-cantilever beam (TDCB) fracture geometry to simplify calculation of healing efficiency to the ratio of healed to virgin critical loads, η = PChealed/ PCvirgin. The current work investigates the application of the TDCB geometry and three common geometries utilized in the broader fracture literature (the compact tension (CT), single-edge notch bend (SENB), and single-edge notch tension (SENT) geometries) to the measurement of healing efficiency. While the TDCB geometry simplifies the calculation of healing efficiency because the crack lengths do not need to be accounted for, it is shown that if the virgin and healed crack lengths are not accurately accounted when using the CT, SENB, and SENT geometries, errors in calculated healing efficiency can be several hundred per cent. The TDCB geometry is reviewed at length, including the underlying theory and experimental calibration and validation of TDCB geometry.