Matrix Crack Networks in SiC/SiC Composites: In-Situ Characterisation and Metrics

2021 ◽  
Author(s):  
S. P. Jordan ◽  
S. P. Jeffs ◽  
C. D. Newton ◽  
L. Gale ◽  
P. I. Nicholson ◽  
...  
Keyword(s):  
Crack Opening ◽  
Ceramic Matrix Composites ◽  
Fatigue Loading ◽  
Matrix Crack ◽  
Matrix Cracking ◽  
Damage Development ◽  
Opening Displacement ◽  
Ongoing Research ◽  
Wide Range

Abstract Ceramic matrix composites can offer clear potential for a variety of engineering applications where the temperature capabilities of conventional metals are exceeded. Continued mechanical characterisation is essential to gain an understanding of their associated damage and failure mechanisms across a wide range of representative temperatures. The present paper will report ongoing research to characterize the initiation of matrix cracking at room temperature under tensile stress and subsequent damage development under fatigue loading in a SiCf/SiC composite. Imaging and mechanical property data were obtained via in-situ loading within a scanning electron microscope. The temporal nature of damage development was also recorded through the selective employment of acoustic emission. Metrics to describe the spatial distribution of cracks, crack lengths and crack opening displacement under load will be presented. The inspections also provided detailed evidence of the associated crack closure phenomena. The understanding of matrix crack saturation and matrix/fibre interfacial mechanics will be explored, together with the implications for the use of X-ray tomographic inspection of engineering components during service. The potential for these emergent techniques as a basis for future CMC characterization, via automated image recognition and machine learning, will be highlighted.

In-Situ NDE Monitoring of Crack Bridging in Ceramic Composites via Crack Opening Displacement

1994 ◽  
Author(s):  
Abhisak Chulya ◽  
John P. Gyekenyesi
Keyword(s):  
Crack Opening ◽  
Ceramic Matrix Composites ◽  
Ceramic Composites ◽  
In Situ Observation ◽  
Matrix Composites ◽  
Opening Displacement ◽  
Crack Bridging ◽  
Interferometric Technique ◽  
Fiber Bridging

A study of crack bridging in long-fiber reinforced ceramic matrix composites (CMC) is the main focus of this paper. The in-situ observation using NDE techniques reveals that 1D SiC/CAS CMCs show only partial fiber bridging behavior while 2D SiC/SiC CMCs possess an excellent bridging mechanism. Laser interferometric technique was successfully applied to measure crack opening displacements (COD) in the notched specimens under four-point flexural loading. The onset of precracking and the effects of fiber bridging were also detected by in-situ optical microscopy and acoustic emission techniques. The applied load-COD relations were shown and on the basis of these results, the bridging stiffness parameter can be determined via the fracture mechanics formulation proposed by Cox and Marshall.

scholarly journals Non-Steady First Matrix Cracking of Fiber-Reinforced Ceramics

2020 ◽  
Author(s):  
Huan Wang
Keyword(s):  
Steady State ◽  
Crack Opening ◽  
Ceramic Matrix Composites ◽  
Matrix Cracking ◽  
Fiber Direction ◽  
Fiber Reinforced ◽  
Opening Displacement ◽  
Interface Shear ◽  
The Matrix ◽  
Lag Model

Matrix cracking affects the reliability and safety of fiber-reinforced ceramic-matrix composites during operation. The matrix cracking can be divided into two types, that is, steady state crack and non-steady state cracking. This chapter is about the non-steady stable cracking of fiber-reinforced CMCs. The micro stress field of fiber, matrix, and interface shear stress along the fiber direction is analyzed using the shear-lag model. The relationship between the crack opening displacement and the crack surface closure traction is derived. The experimental first matrix cracking stress of different CMCs are predicted.

Durability and Damage Development in Woven Ceramic Matrix Composites Under Tensile and Fatigue Loading at Room and Elevated Temperatures

2000 ◽  
Vol 122 (4) ◽  
pp. 394-401 ◽  
Author(s):  
A. Haque ◽  
M. Rahman
Keyword(s):  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Failure Strain ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Matrix Cracking ◽  
Woven Composites ◽  
Rate Equations ◽  
Matrix Composites ◽  
Damage Development

This paper investigates the damage development in SiC/SiNC woven composites under tensile and cyclic loading both at room and elevated temperatures. The ultimate strength, failure strain, proportional limit, and modulus data at a temperature range of 23°C–1250°C are generated. The tensile strength of SiC/SiNC woven composites has been observed to increase with increased temperatures up to 1000°C. The stress/strain plot shows a pseudo-yield point at 25 percent of the failure strain εf, which indicates damage initiation in the form of matrix cracking. The evolution of damage above 0.25 εf both at room and elevated temperature comprises of multiple matrix cracking, interfacial debonding, and fiber pullout. Although the nature of the stress/strain plot shows damage-tolerant behavior under static loading both at room and elevated temperature, the life expectancy of SiC/SiNC composites degrades significantly under cyclic loading at elevated temperature. This is mostly due to the interactions of fatigue damage caused by the mechanically induced plastic strain and the damage developed by the creep strain. The in-situ damage evolutions are monitored by acoustic event parameters, ultrasonic C-scan, and stiffness degradation. Rate equations for modulus degradation and fatigue life prediction of ceramic matrix composites both at room and elevated temperatures are developed. These rate equations are observed to show reasonable agreement with experimental results. [S0094-4289(00)02304-5]

In-Situ Estimation of Surface Crack Shape From Crack Opening Displacement by Use of NCOD Database System

2010 ◽  
Author(s):  
Jingxia Yue ◽  
Zheng He ◽  
Yukio Fujimoto ◽  
Weiguo Wu
Keyword(s):  
Crack Opening Displacement ◽  
Surface Crack ◽  
Fatigue Cracks ◽  
Crack Opening ◽  
Crack Depth ◽  
Database System ◽  
Shape Estimation ◽  
Opening Displacement ◽  
Crack Shape

This paper proposes an in-situ estimation of crack shape from crack opening displacement (COD) by using of a visualized database system consisting of numerical calculation data of normalized crack opening displacement (NCOD) for some kinds of crack types. The relation between crack depth and corresponding NCOD is discussed based on FE analysis results, from which a crack shape estimation principle is deduced. Visualized software named NCOD Database System was developed to facilitate convenient in-situ estimation of crack shape. Shapes of three kinds of surface crack, partial circle crack in plate, fatigue cracks in gusset weld joint and in large-scale member, are successfully estimated by this system. The paper is supported by the Programme of Introducing Talents of Discipline to Universities (B08031).

scholarly journals Effect of Cyclic Fatigue Loading on Matrix Multiple Fracture of Fiber-Reinforced Ceramic-Matrix Composites

Ceramics ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 327-346 ◽  
Author(s):  
Longbiao Li
Keyword(s):  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Fatigue Loading ◽  
Cyclic Fatigue ◽  
Matrix Cracking ◽  
Matrix Composites ◽  
Matrix Interface ◽  
Multiple Fracture ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

In this paper, the effect of cyclic fatigue loading on matrix multiple fracture of fiber-reinforced ceramic-matrix composites (CMCs) is investigated using the critical matrix strain energy (CMSE) criterion. The relationships between multiple matrix cracking, cyclic fatigue peak stress, fiber/matrix interface wear, and debonding are established. The effects of fiber volume fraction, fiber/matrix interface shear stress, and applied cycle number on matrix multiple fracture and fiber/matrix interface debonding and interface wear are discussed. Comparisons of multiple matrix cracking with/without cyclic fatigue loading are analyzed. The experimental matrix cracking of unidirectional SiC/CAS, SiC/SiC, SiC/Borosilicate, and mini-SiC/SiC composites with/without cyclic fatigue loading are predicted.

Matrix Cracking In Brittle-Matrix Composites with Tailored Interfaces

1994 ◽  
Vol 365 ◽  
Author(s):  
Sawai Danchaivijit ◽  
L-Y. Chao ◽  
D. K. Shetfty
Keyword(s):  
Steady State ◽  
Crack Length ◽  
Uniaxial Tension ◽  
Sliding Friction ◽  
Crack Opening ◽  
State Theory ◽  
Matrix Cracking ◽  
Opening Displacement ◽  
The Matrix ◽  
Cracking Stress

ABSTRACTMatrix cracking from controlled through cracks with bridging filaments was studied in a model unidirectional composite of SiC filaments in an epoxy-bonded alumina matrix. An unbonded, frictional interface was produced by moderating the curing shrinkage of the epoxy with the alumina filler and coating the filaments with a releasing agent. Uniaxial tension test specimens (2.5 × 25 × 125 mm) with filament-bridged through cracks were fabricated by a novel two-step casting technique involving casting, precracking and joining of cracked and uncracked sections. Distinct matrix-cracking stresses, corresponding to the extension of the filamentbridged cracks, were measured in uniaxial tension tests using a high-sensitivity extensometer. The crack-length dependence of the matrix-cracking stress was found to be in good agreement with the prediction of a fracture-mechanics analysis that employed a new crack-closure force - crack-opening displacement relation in the calculation of the stress intensity for fiber-bridged cracks. The prediction was based on independent experimental measurements of the matrix fracture toughness (Kcm), the interfacial sliding friction stress (τ) and the residual stress in the matrix (σmI). The matrix-cracking stress for crack lengths (2a) greater than 3 mm was independent of the crack length and agreed with the prediction of the steady-state theory of Budiansky, Hutchinson and Evans[2]. Tests on specimens without the deliberately introduced cracks indicated a matrix-cracking stress significantly higher than the steady-state stress.

Combined In Situ X-Ray Computed Tomography and Acoustic Emission Analysis for Composite Characterization - A Feasibility Study

2019 ◽  
Vol 809 ◽  
pp. 604-609
Author(s):  
Miriam Bartkowiak ◽  
Ludwig Schoettl ◽  
Peter Elsner ◽  
Kay André Weidenmann
Keyword(s):  
Computed Tomography ◽  
Acoustic Emission ◽  
Matrix Cracking ◽  
Bending Test ◽  
Fiber Reinforced ◽  
Interface Failure ◽  
Emission Analysis ◽  
Damage Mechanisms ◽  
Wide Range

Fiber reinforced plastics show a wide range of different damage mechanisms such as matrix cracking, fiber breakage and interface failure. These can be observed in damaged specimens by means of volumetric images acquired by computed tomography (CT). As each failure mechanism causes a characteristic acoustic emission (AE) signal, AE analysis is a promising tool to identify damage mechanisms and offers the advantage that a real-time observation of the damage evolution during the testing period is possible. For a correlation of damage mechanisms and AE events, AE analysis was combined with in- situ CT measurements. This combined approach was validated by means of a 3-point-bending test on a discontinuous glass fiber reinforced sheet molding compound (GF-SMC) in which AE signals were acquired during loading using two high frequency piezoelectric sensors. At times of increasing AE activity, the test was interrupted in order to carry out a CT-scan of the specimen under load. AE events could subsequently be linked with the damage mechanisms observed in the CT-scans at different stages of damage to identify signal features that are characteristic for a certain mechanism. The sources of the signals could be localized and were in line with the actual location of damage.

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