Failure Fibrous

Fibrous or particulate filters are not important anymore because membrane filters are relatively compac t and perform veiy well. For filtration by straining, there is an intermediate air velocity at which filtration efficiency is a minimum because different collec tion mechanisms predominate at different ranges of velocity. At low velocities, diffusional and elec trostatic forces on the particle are important, and increased velocity shortens the time for them to operate. At high velocities, inertial forces that increase with air velocity come into play below a certain air velocity, their effect on collection is zero. Surges or brief power failures could change velocity and collection efficiency. 

B. Walter Rosen, Tensile Failure of Fibrous Composites, AIAA Journal, November 1964, pp. 1985-1991. 

Based on this analysis it is evident that materials which are biaxially oriented will have good puncture resistance. Highly polar polymers would be resistant to puncture failure because of their tendency to increase in strength when stretched. The addition of randomly dispersed fibrous filler will also add resistance to puncture loads. From some examples such as oriented polyethylene glycol terephthalate (Mylar), vulcanized fiber, and oriented nylon, it is evident that these materials meet one or more of the conditions reviewed. Products and plastics that meet with puncture loading conditions in applications can be reinforced against this type of stress by use of a surface layer of plastic with good puncture resistance. Resistance of the surface layer to puncture will protect the product from puncture loads. An example of this type of application is the addition of an oriented PS layer to foam cups to improve their performance. 

Rosen, B.W. (1964). Tensile failure of fibrous composites. AlAA J. 2, 1985-1991. 

Wilkins, D.J. (1983). Failure analysis and mechanisms of failure of fibrous composite structures. NASA CP-2278, 67-93. 

FE data have been collected from the fracture of a wide variety of single and multi-component solids, ranging from single crystals of molecular solids to fiber-reinforced composites, and also from the peeling of adhesives 0-16 ). In this paper, we will restrict our attention to FE arising from the failure of polymer composites (fibrous and particulate), and the individual components thereof (fibers and matrix resins). 

The increasing use of high-performance fibrous composites in critical structural applications has led to a need to predict the lifetimes of these materials in service environments. To predict the durability of a composite in service environment requires a basic understanding of (1) the microscopic deformation and failure processes of the composite (2) the significance of the fiber, epoxy matrix and fiber-matrix interfacial region in composite performance and (3) the relations between the structure, deformation and failure processes and mechanical response of the fiber, epoxy matrix and their interface and how such relations are modified by environmental factors. 

Types I, II, and III collagen form the fibrous network that prevents premature mechanical failure of most tissues and acts to transmit stress to and from cells. The molecular sequences of these collagens are known and they are composed of approximately 1000 amino acids in the form of Gly-X-Y with small nonhelical ends before and after these sequences. All of these collagen types form continuous triple-helical structures that pack laterally... 

It is well documented [2-4] that the precursor to fracture in PE is the failure of the craze structure ahead of the crack tip during SCO, The formation of the craze and the mechanism that leads to craze breakdown have been described frequently. The craze nucleation is characterised by the formation of a highly localised zone ahead of the crack tip which consists of multiple voids. Their growth and subsequent coalescence leads to the formation of a fibrous structure. Depending on the stability of the craze structure, the craze may widen by drawing material from the craze-bulk interface into the craze fibrils and eventually rupture at the midribs, or fail at the craze-bulk interface with little or no signs of material fibrillation [5],... 

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