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.

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.

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.

scholarly journals Effect of Processing Residual Stresses on Stress-Strain Behavior of Brittle Matrix Composites

1996 ◽  
Vol 5 (2) ◽  
pp. 096369359600500
Author(s):  
A. A. Giannakopoulou ◽  
E. E. Gdoutos
Keyword(s):  
Residual Stresses ◽  
Strain Curve ◽  
Analytical Investigation ◽  
Matrix Cracking ◽  
Matrix Composites ◽  
Stress Strain ◽  
Brittle Matrix ◽  
Strain Behavior ◽  
Brittle Matrix Composites ◽  
Level Of Processing

An analytical investigation of the effect of processing residual stresses on the longitudinal tensile behavior of unidirectional brittle matrix composites was undertaken. The study was based on a modified shear lag analysis. From the results of the investigation the dependence of the macroscopic stress-strain curve and the microscopic failure mechanisms including matrix cracking initiation and multiplication, and fiber debonding on the level of processing residual stresses was established.

Improving Fracture Toughness of Brittle Matrix Composites Using End-Shaped Ductile Fibers: The Effects of Adhesion and Matrix Shrinkage

Materials ◽  
2003 ◽  
Author(s):  
Robert C. Wetherhold ◽  
Renee M. Bagwell
Keyword(s):  
Fracture Toughness ◽  
Bond Strength ◽  
Surface Chemistry ◽  
Matrix Composites ◽  
Release Agent ◽  
Brittle Matrix ◽  
Matrix Shrinkage ◽  
Pull Out ◽  
Brittle Matrix Composites ◽  
The Matrix

Ductile fibers are added to brittle matrix composites to increase the fracture toughness. To further improve fracture toughness, end shaped ductile fibers are added to act as anchors to utilize more of the fibers’ plasticity. Previous research focused on optimizing the volume of the shaped end for a given end shape family. Results indicate that for a given end shape family there is an optimum volume; above or below this volume results in a lower fracture toughness contribution. This research investigates two additional factors, adhesion of the matrix to the fiber and matrix shrinkage, and determines their effects on the fracture toughening of brittle matrix composites. The fiber was an annealed copper and the matrices used were a low shrinkage epoxy, a high shrinkage epoxy, and polyester. Results indicate that controlling the surface chemistry of the fiber can give an additional degree of freedom to the utilization of the fiber plasticity, although the importance of this control depends on the particular system. The fiber surface chemistry affects the bond strength and the adhesion; if the fiber cannot debond from the matrix, then shaping the end does not permit use of the plastic potential. Depending on the system, the adhesion and bond strength of the matrix to the fiber significantly affects the amount of fiber plasticity utilized. To determine the effects of friction and matrix shrinkage on the utilization of the fiber plasticity, release agent was applied to the end shaped fibers to reduce the adhesion, bond strength, and friction during pull out. Results indicate that frictional work and adhesion has a large impact on the utilization of the fiber plasticity; with release agent, the end shaped fiber utilizes little of the fiber plasticity. Furthermore, this indicates that for the matrices investigated, matrix shrinkage has a minor influence on the utilization of the fiber plasticity.

Sign in / Sign up

Export Citation Format

Share Document