Quantification of crack area in ceramic matrix composites at single-fiber push-out testing and influence of pyrocarbon fiber coating thickness on interfacial fracture toughness

Abstract

For mechanical characterization of interfacial properties in fiber-reinforced ceramic matrix composites by single-fiber push-out tests, a determination of the relevant crack area is required. In established evaluation methods, the relevant crack area is approximated by the total cylindrical fiber surface of the pushed fiber. This concept disregards that stable crack propagation, which is relevant for prediction of macromechanical behavior, may occur on just part of the fiber-matrix interface area. In the present publication, a new approach to quantify the relevant crack area is presented, enabling a more reliable determination of the interfacial fracture toughness of ceramic matrix composites.The new concept is applied to SiC-fiber reinforced SiC-matrix composites with pyrocarbon fiber coatings (SiC/PyC/SiC) produced via chemical vapor infiltration technique. The occurrence of stable and unstable crack growth, as predicted in literature, can be verified experimentally. A strong correlation between PyC fiber coating thickness and interfacial fracture toughness is found.

Interface Controlled Micro- and Macro-Mechanical Properties of Vibration Processed Carbon Fiber/Epoxy Composites

“…Figure 7 e,f show that applying the random vibration into the curing process of composite laminates production improved the resin fluidity, which helps to eliminate micro-defects around the fiber-resin interface and then provides composites with strong adhesion between fibers and the matrix. In these cases, voids and existing micro-cracks are no longer the main reason for push-out failure, and the emanation and propagation of cracks need higher overall energy absorbed during the process of interface debonding and interface sliding [ 43 , 44 , 45 ]. However, if vibration acceleration exceeded 10 g, the location and characteristics of micro-defects were similar to the pattern cured under low pressures, and these critical imperfections caused by poor wettability of the resin matrix to carbon fibers will induce the fiber-resin interface failure in an easy way.…”

3D printing as an automated manufacturing method for a carbon fiber-reinforced cementitious composite with outstanding flexural strength (105 N/mm2)

“…The curve shows an abrupt load drop at an indenter displacement of approximately 0.86 lm. Here, complete fiber debonding and fiber push-out, i.e., an abrupt relative movement of the fiber toward the back side of the sample, was achieved [35,38]. To date, abrupt push-out behavior during cyclic loading has been reported for fiber-reinforced ceramics (SiC/SiC) [38] and carbon fiber-reinforced polymers [35,36,39,40].…”

Evaluation of the creep behaviour of the carbon fibre in an unidirectional pultruded reinforced composite using nano-indentation technique

“…The typical impression mark was visible on the fibre after the removal of the load as seen in Figure 10b. Mueller measured the imprint and push-in of the glass fibre by AFM after push-out test and the depth was about 200 nm [29]. A load-displacement curve like B30-1-120_x was frequently found when test piece was placed on the EDM machined wide grooves, and this was majorly due to a span of 100µm led to larger deformation of the thin slice under load resulted in an elastic bending of the thin sample between the supports which was also reported earlier [19].…”