Correlating Electrical Resistance Change with Mechanical Damage in Woven SiC/SiC Composites: Experiment and Modeling

Abstract

Silicon carbide (SiC) fiber‐reinforced SiC matrix composites are inherently multifunctional materials. In addition to their primary function as a structural material, the electric properties of the SiC/SiC composites could be used for the sensing and monitoring of in situ damage nucleation and evolution. To detect damage and use that information to further predict the useful life of a particular component, it is necessary to establish the relationship between damage and electrical resistance change. Here, two typical SiC/SiC composites, melt infiltrated (MI), and chemical vapor infiltrated (CVI) woven SiC/SiC composites, were tested to establish the relationship between the electrical response and mechanical damage in unload–reload tensile hysteresis tests. Compared to the 55% resistance increase seen for CVI composites, the MI SiC/SiC composites exhibit a maximum resistance change in 450% in response to mechanical loading (damage), which is the highest sensitivity known among various composites. An analytic model accounting for fiber breakage and matrix cracks was developed to link the electrical resistance to mechanical damage in the composites. The predictions from the models agree well with the experimental data for both composites with high and low conductive matrices. The residual resistance change after unloading is also correlated to the loading history by the analytical relationship. This study demonstrates that resistance change is sensitive to damage in a predictable manner and can be used to improve the reliability of damage assessment of SiC/SiC composites.

Monitoring damage evolution of SiCf/[Si B C]m composites using electrical resistivity: Crack density-based electromechanical modeling

“…A representation of the composite similar to the one proposed in [23] is considered, as a network of cells set out parallel and in series (Fig. 7b), and then adapted to the Cerasep®A40C material considered in the present work.…”

“…The damage mode leading to an increase of the resistance is considered, for these materials, to be fiber breakage, describing the strength of fibers by a Weibull distribution function. Regarding CMCs, an analytical model [23] inspired by previous work on CFRPs has been proposed, accounting for both fiber breakage and matrix cracks. The probability of fracture of a fiber is also described by a Weibull distribution function, and fiber fractures are introduced as ruptures in the analytical resistor network.…”

“…In this work, an electrical resistor network model is proposed with a geometry close to the one used by [23], but considering transverse matrix cracking as the main damage mode leading to an increase in the resistance. This model is adapted to the material of the study with a CVI matrix based on the [Si-B-C] system, which presents a relatively low conductivity, and a pyrocarbon interphase with a high electrical conductivity.…”

“…Moreover, the introduction of mechanical damage in the electrical model is a key issue for a satisfying coupling between electrical and mechanical behaviors. This damage was previously introduced as a Weibull distribution for fiber breakage [23] with extra parameters to be fitted, or through micromechanical analytical expressions [19], yet with difficulties to obtain a precise estimation of debonding lengths. In this work, it is proposed to derive mechanical damage indicators directly from the stress-strain behavior of the tested material (using unloading-reloading cycles), and to use them in the electrical model.…”

Damage investigation and modeling of 3D woven ceramic matrix composites from X-ray tomography in-situ tensile tests

“…Experimental studies of damage mechanisms in melt infiltrated (MI) SiC/SiC composite have relied on electrical resistance change [5], acoustic emission and 2D microscopic observations [6], [7]. These studies revealed that matrix cracks initiate in weft tows and in the matrix-rich regions.…”