Mechanics of matrix cracking in brittle-matrix fibre-reinforced composites

1987 ◽  
Vol 409 (1837) ◽  
pp. 329-350 ◽  
Keyword(s):  
Energy Balance ◽  
Crack Opening ◽  
Crack Problem ◽  
Matrix Cracking ◽  
Matrix Composites ◽  
Entire Cross Section ◽  
Brittle Matrix ◽  
Matrix Cracks ◽  
The Matrix ◽  
Cracking Stress

Energy-balance calculations for a continuum model of cracking in a uniaxially fibre-reinforced composite having a brittle matrix are presen­ted. It is assumed that the fibres are strong enough to remain intact when the matrix cracks across the entire cross section of the composite. By equating the energy availability for the cracking of continuum and discrete fibre models it is shown how the crack boundary condition relating fibre stress to crack opening must be selected. It is confirmed that the Griffith fracture criterion is valid for matrix cracking in composites. By considering the energy balance of long cracks it is shown that the limiting value of the stress intensity factor is independent of crack length and that it predicts a matrix-cracking strain that is consistent with the known result. An improved numerical method is described for solving a crack problem arising from the study of the cracking of brittle-matrix composites. Numerical results of high accuracy are obtained, which show how the cracking stress is related to the size of a pre-existing defect. Of special significance is the prediction of the correct threshold stress (i.e. matrix­-cracking stress) below which matrix cracking is impossible no matter how large the pre-existing defect.

Stochastic Aspects of Matrix Cracking in Brittle Matrix Composites

1993 ◽  
Vol 115 (3) ◽  
pp. 314-318 ◽  
Author(s):  
S. M. Spearing ◽  
F. W. Zok
Keyword(s):  
Matrix Cracking ◽  
Matrix Composites ◽  
Brittle Matrix ◽  
Tensile Response ◽  
Brittle Matrix Composites ◽  
Crack Interactions ◽  
The Matrix ◽  
Interface Slip ◽  
Bridging Fibers

A computer simulation of multiple cracking in fiber-reinforced brittle matrix composites has been conducted, with emphasis on the role of the matrix flaw distribution. The simulations incorporate the effect of bridging fibers on the stress required for cracking. Both short and long (steady-state) flaws are considered. Furthermore, the effects of crack interactions (through the overlap of interface slip lengths) are incorporated. The influence of the crack distribution on the tensile response of such composites is also examined.

Matrix cracking and the mechanical behaviour of SiC─CAS composites

1992 ◽  
Vol 437 (1899) ◽  
pp. 109-131 ◽  
Keyword(s):  
Elastic Properties ◽  
Three Dimensional ◽  
Matrix Cracking ◽  
Repeated Loading ◽  
Matrix Composites ◽  
Pull Out ◽  
Matrix Cracks ◽  
Brittle Matrix Composites ◽  
Dimensional Network ◽  
The Matrix

An experimental investigation has been carried out on the mechanical properties of unidirectional (0) 12 , (0, 90) 3S , (±45, 0 2 ) S , and (±45) 3S composites consisting of CAS glass ceramic reinforced with Nicalon SiC fibres. Measurements have been made of the elastic properties and of the tensile, compression and shear strengths of the composites, and these have been supported by a detailed study of the damage which occurs during monotonic and repeated loading. These damage studies have been carried out by means of edge replication microscopy and acoustic emission monitoring. The elastic properties of the composites are, by and large, close to the values that would be predicted from the constituent properties and lay-up sequences, but their strengths are lower than expected, and it appears that the Nicalon reinforcing fibre has been seriously degraded during manufacture. The fracture energy is much higher than predicted from observations of fibre pull-out, and it is suggested that the energy required to form a close three-dimensional network of matrix cracks could account for the high apparent toughness. The matrix cracking stress can be predicted reasonably closely by the Aveston, Cooper and Kelly model of cracking in brittle matrix composites, but it is shown that subcritical microcracks can form and/or grow at stresses well below the predicted critical values without affecting composite properties.

Stability Analysis of Bridged Cracks in Brittle Matrix Composites

1993 ◽  
Vol 115 (1) ◽  
pp. 127-138 ◽  
Author(s):  
R. Ballarini ◽  
S. Muju
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Opening ◽  
Matrix Crack ◽  
Matrix Composites ◽  
Brittle Matrix ◽  
Matrix Cracks ◽  
Brittle Matrix Composites ◽  
Propagating Crack

The bridging of matrix cracks by fibers is an important toughening mechanism in fiber-reinforced brittle matrix composites. This paper presents the results of a nonlinear finite element analysis of the Mode I propagation of a bridged matrix crack in a finite size specimen. The composite is modeled as an orthotropic continuum and the bridging due to the fibers is modeled as a distribution of tractions that resist crack opening. A critical stress intensity factor criterion is employed for matrix crack propagation, while a critical crack opening condition is used for fiber failure. The structural response of the specimen (load-deflection curves) as well as the stress intensity factor of the propagating crack is calculated for various constituent properties and specimen configurations for both tensile and bending loading. By controlling the length of the bridged crack, results are obtained that highlight the transition from stable to unstable behavior of the propagating crack.

Stability Analysis of Bridged Cracks in Brittle Matrix Composites

1991 ◽  
Author(s):  
Roberto Ballarini ◽  
Sandeep Muju
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Opening ◽  
Matrix Crack ◽  
Matrix Composites ◽  
Brittle Matrix ◽  
Matrix Cracks ◽  
Brittle Matrix Composites ◽  
Propagating Crack

The bridging of matrix cracks by fibers is an important toughening mechanism in fiber reinforced brittle matrix composites. This paper presents the results of a non-linear finite element analysis of the Mode-I propagation of a bridged matrix crack in a finite size specimen. The composite is modeled as an orthotropic continuum and the bridging due to the fibers is modeled as a distribution of tractions which resist crack opening. A critical stress intensity factor criterion is employed for matrix crack propagation while a critical crack opening condition is used for fiber failure. The structural response of the specimen (load-deflection curves) as well as the stress intensity factor of the propagating crack are calculated for various constituent properties and specimen configurations for both tensile and bending loading. By controlling the length of the bridged crack results are obtained which highlight the transition from stable to unstable behavior of the propagating crack.

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.

Effect of temperature on matrix multicracking evolution of C/SiC fiber-reinforced ceramic-matrix composites

2020 ◽  
Vol 39 (1) ◽  
pp. 189-199
Author(s):  
Longbiao Li
Keyword(s):  
Strain Energy ◽  
Ceramic Matrix Composites ◽  
Critical Value ◽  
Matrix Cracking ◽  
Interface Debonding ◽  
Matrix Composites ◽  
Temperature Dependent ◽  
Damage State ◽  
The Matrix ◽  
Sic Composites

AbstractIn this paper, the temperature-dependent matrix multicracking evolution of carbon-fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs) is investigated. The temperature-dependent composite microstress field is obtained by combining the shear-lag model and temperature-dependent material properties and damage models. The critical matrix strain energy criterion assumes that the strain energy in the matrix has a critical value. With increasing applied stress, when the matrix strain energy is higher than the critical value, more matrix cracks and interface debonding occur to dissipate the additional energy. Based on the composite damage state, the temperature-dependent matrix strain energy and its critical value are obtained. The relationships among applied stress, matrix cracking state, interface damage state, and environmental temperature are established. The effects of interfacial properties, material properties, and environmental temperature on temperature-dependent matrix multiple fracture evolution of C/SiC composites are analyzed. The experimental evolution of matrix multiple fracture and fraction of the interface debonding of C/SiC composites at elevated temperatures are predicted. When the interface shear stress increases, the debonding resistance at the interface increases, leading to the decrease of the debonding fraction at the interface, and the stress transfer capacity between the fiber and the matrix increases, leading to the higher first matrix cracking stress, saturation matrix cracking stress, and saturation matrix cracking density.

Role of interface properties on the toughness of brittle matrix composites reinforced with ductile fibers

1992 ◽  
Vol 7 (11) ◽  
pp. 3132-3138 ◽  
Author(s):  
H.E. Dève ◽  
S. Schmauder
Keyword(s):  
Fracture Resistance ◽  
Crack Opening ◽  
Geometrical Model ◽  
Interface Properties ◽  
Matrix Composites ◽  
Brittle Matrix Composites ◽  
The Matrix ◽  
Interface Sliding ◽  
Brittle Composites

The incorporation of ductile fibers in brittle matrices can lead to a significant increase in fracture resistance. The increase in toughness that derives from crack bridging is governed by the properties of the matrix/fiber interface and the ductility of the fibers. The current study addresses the role of interface sliding stress on the toughness of brittle composites reinforced with ductile fibers. The debond length is explicitly related to the interface sliding stress and the properties of the fiber. It is then incorporated into a geometrical model to simulate the bridging tractions versus crack opening under condition of continuous debonding. The implications on the effect of interfaces on the resistance curve are discussed.

scholarly journals Micromechanical Analyses of Debonding and Matrix Cracking in Dual-Phase Materials

2016 ◽  
Vol 83 (5) ◽  
Author(s):  
Brian Nyvang Legarth ◽  
Qingda Yang
Keyword(s):  
Biaxial Loading ◽  
Matrix Cracking ◽  
Dual Phase ◽  
Load Carrying Capacity ◽  
Matrix Cracks ◽  
Loading Direction ◽  
Load Carrying ◽  
The Matrix ◽  
Cohesive Zones ◽  
Good Agreement

Failure in elastic dual-phase materials under transverse tension is studied numerically. Cohesive zones represent failure along the interface and the augmented finite element method (A-FEM) is used for matrix cracking. Matrix cracks are formed at an angle of 55 deg−60 deg relative to the loading direction, which is in good agreement with experiments. Matrix cracks initiate at the tip of the debond, and for equi-biaxial loading cracks are formed at both tips. For elliptical reinforcement the matrix cracks initiate at the narrow end of the ellipse. The load carrying capacity is highest for ligaments in the loading direction greater than that of the transverse direction.

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