Particulate composites fracture

T.-J. Chuang, D. F. Carroll, and S. M. Wiederhom Creep Rupture of a Metal-Ceramic Particulate Composite, Seventh International Conference on Fracture, in Advances in Fracture Research, Vol. 4, eds., K. Salama, K. Ravi-Chandler, D. M. R. Taplin, and P. Rama Rao, Pergamon Press, New York, NY, 1989, pp. 2965-2976. 

Landes and has since received wide attention. As yet, there are no published papers describing the direct measurement of. rubber-tou ened plastics or other particulate composites. Williams and co-workers have attempted to estimate Jjc for HIPS and ABS indirectly, from the work done at the crack tip in SEN specimens sulqected to tenaon or bending As the fracture surfaces were extensively whitened, these estimates were probably hi the 7/ criterion should strictly be applied to the point of crack initiation rather tiian to later stages of ductile tearing. 

FIGURE 6. Typical examples of fracture surfaces showing fracture origins for (a) 0 mol% (10-YSZ) (b) 30mol% alumina particulate composite [2]. Bar = 500 p,m. Reprinted with permission of The American Ceramic Society, www.ceramics.org. Copyright [2002]. 

FIGURE 11. Fracture toughness as a function of alumina content for 10-YS alumina particulate and platelet composites at lOtXPC in air [2, 5, 6]. Flexure toughness of 10-YSZ/alumina particulate composites [2, 5, 6] is included for comparison. Error bars indicate 1.0 standard deviations. The lines represent the best fit... 

As seen from the aforementioned properties, the maximum flexure strength at 1000°C was achieved for the 30 mol% particulate composite, while the maximum fracture toughness at 1000°C was attained for the 30 mol% platelet composite. The resistance to SCG susceptibility was greater in the 30 mol% platelet composite with a higher SCG parameter of n = 33 than in the 30 mol% particulate composite with a lower SCG parameter of n = 6. 

With respect to elevated-temperature strength, the 30 mol% particulate composite is better than the platelet counterpart. In contrast, with regard to fracture toughness and SCG... 

At 1000°C, the 30 mol% particulate composites yielded the maximum strength, whereas the 30 mol% platelet composite exhibited the maximum fracture toughness. Fracture toughness was approximately 16% greater in the platelet composites than in the particulate composites. 

Hybrid aluminosilicate glass matrix composite with Nicalon fibre and SiC particulate reinforcement Fracture strength 778 MPa-827 MPa (depending of SiC particulate content) High-lemperature aerospace applications [74]... 

T. L. lessen and D. Lewis III, Effect of Composite Layering on the Fracture Toughness of Brittle Matrix/Particulate Composites, Composites 26, 67-71 (1995). 

The extended finite element method (XFEM) for treating fracture in composite materials is proposed by Huynh and Belytschko [191]. This methods work with meshes that are independent of matrix/inclusion interfaces and the discontinuities and neartip enrichments were modeled. In order to describe the geometry of the interfaces and cracks in this method, level sets were employed, so that there is no need for explicit representation of either the cracks or the material interfaces. The other researchers such as Du et al. [192] and Ying et al. [193] used XFEM to model material interfaces in particulate composites with more in detail. 

In this chapter, the fracture of WPCs as particle-filled polymer composites was elaborated. The characterization of particulate polymer composites fracture behavior and the influencing factors such as particle size as well as orientation, temperature, and loading were discussed. The fracture observation using special setup was described and the diverse numerical methods to analyze the fracture of such composites were reviewed. Finally the finite element simulation of the fracture for WPG specimen with real geometrical model was conducted and the agreement of results compared to the experimental ones was demonstrated. 

The interphase is a three-dimensional (3-D) layer in the immediate vicinity of filler surface, possessing physical properties different from the two main phases or components in a composite (i.e., matrix and filler). For the purpose of this chapter, the term interphase is limited to the layers introduced on the filler surface intentionally in a controlled maimer—engineered interphase layers (EIL). In these layers, a gradient of chemical composition can also exist as well as a gradient of physical properties. The pivotal problem is therefore a definition and an evaluation of an interphase thickness and its properties, namely, stiffness and fracture toughness. Interphase behavior plays a paramount role in the ability to transfer loads from the matrix to the reinforcements, hydrolytic stability of the material, and fracture behavior of a particulate composite. 

The urethane methacrylate polymer which contains no soft-block and the ethoxylated bisphenol A/MMA copolymer both have relatively low values of K q and their composites have fracture toughnesses approximately double that of the respective polymer. The urethane methacrylate polymer which contains a polyol soft-block, on the other hand, has a fracture toughness which is approximately twice that of the other polymers, but for the composite Kiq is increased only modestly. Thus, the higher the fracture toughness of the polymer then the less is the fracture toughness of the particulate composite enhanced relative to it. 

Adhesives Nearly all adhesives are polymers and are used extensively to connect structural components made of wood, composites, metals, polymers, and other materials. Though the amount of adhesive needed for a particular application is small, the cost of a polymer adhesive is high compared to other applications. For example, it is not unusual for an adhesive to cost on the order of 1.00 or more per ounce while general use polymers of the same type might cost less than 1.00 per pound (see Table 3.1). For this and other reasons, the world market for adhesives is in excess of five billion dollars per year. As mentioned earlier, adhesives often contain elastomeric particles to enhance their fracture toughness. In addition, many adhesives contain alumina or other metallic particles for increased tensile and shear strength and in such cases are in reality particulate composites. 

Fig. 3.6 Fracture toughness Kic, versus tensile strength Oc, for found with particulate composites. Note the data ate for nearly theoretically dense composites, produced in a single laboratory by using identical processing in this case variations of secondary factors have a minor influence on the results...

Polycrystals and Particulate Composates vs. the Basic Equation of Linear Fracture Mechanics Up to a certain volume fraction of dispersed particles,F g, a substantial increase in mechanical strength o and/or fracture toughness K/c can be attained here, and it is of interest to consider the factors which play here a role. The discussion is limited to polycrystals and particulate composites where variations of porosity and grain size influence their inherent properties to a minor degree, and these materials fulfil the basic equation of linear fracture mechanics (3.8). 

Many studies on the fracture toughness of particulate composites consider the crack-bowing mechanism as the main toughening mechanism. Lange (1970) first... 

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