Fracture toughness of Al2O3 fibers with an artificial notch introduced by a focused-ion-beam

Determining the mechanism controlling glass fibre strength loss during thermal recycling of waste composites

“…The fracture stress properties of the heat-treated fibres were compared against E-glass fibres which contained a single nano-sized surface flaw of controlled size that was artificially created using focussed ion beam (FIB) milling. FIB milling has been used to determine the fracture properties of brittle carbon and alumina fibres [24][25][26], but the technique has not been previously applied to E-glass fibres. Evaluation of the fracture toughness of the glass fibres is fundamental to determine any changes in the flaw-strength relationship caused by thermal recycling.…”

Estimation of Fracture Toughness of SiC Fiber and Statistical Analysis of Change in Fracture Strength Distribution with Notch Size

“…In the range of small a (<a c where a c satisfies · F0 = · FN at C), · FN is higher than · F0 , which means that the introduced artificial notch is smaller than the intrinsic defect and the fiber is fractured not by the notch but by the intrinsic defect. 14,25) Accordingly, the actual fracture strength · F is given by · F0 . On the other hand, in the range of large a (>a c ), · FN is lower than · F0 , which means that the notch is larger than intrinsic defect and the fiber is fractured by the notch, not by the intrinsic defect.…”

“…In estimation of fracture toughness of these small diameter fibers, the difficulties arise from the small physical dimensions, due to which proper method to introduce small notches is limited. To overcome the difficulties, a procedure to introduce a sharp artificial notch into small diameter fiber by a micromachining method using a focused-ion-beam (FIB) has been developed recently by the authors 1215) and Ogihara et al 16,17) With this method, a sharp mode I type straight-fronted edge notch with notch-tip radius around 25 nm could be introduced in polycrystalline 12) and amorphous 13) SiC fibers, two types of the Al 2 O 3 fibers with different microstructure to each other, 14) and pitch-based 15) and PAN-based 16,17) carbon fibers, and the fracture toughness of these fibers could be estimated successfully.…”

In Situ tensile tests to analyze the mechanical response, crack initiation, and crack propagation in single polyamide 66 fibers

“…Naito et al systematically observed the fracture surfaces of broken carbon fibers from single fibers tested in tension and identified similar fracture patterns independently of the gauge length. Other recent pioneer works have used the focused ion beam (FIB) technique so as to introduce a notch at single fiber scale on brittle fibers such as silicon carbide, carbon fibers, and so forth. This single edge notched tensile (SENT) like geometry allowed the fracture toughness of these fibers to be determined with a two‐dimensional (2D) or three‐dimensional (3D) approach.…”