Ductility tough materials

Selection of tough materials, with high ductility,... 

The method has been applied to numerous ductile polymeric materials [Begley and Landes, 1972 Landes and Begley, 1974]. The critical J values obtained by using single specimen method were greater than those obtained from the standard multiple-specimen method [Westerlind et al., 1991]. Many workers have used the ASTM standards of E813-87 to characterize the fracture toughness of polymers [Chan and Williams, 1981,... 

Along with the plasticizer concentration increase the stiffness and the toughness decrease and ductility of material increases. Figure 10.17 shows the effect of polar plas-... 

Cracks are less important for tough materials (e.g. rubber, plastics and metals) since excess strain energy is used in deformation of the material rather than crack propagation. Thus in ductile metals, for example the stress concentration at the top of a crack will cause deformation of the material around the crack tip, resulting in a larger tip radius and lower stress concentration. 

P/M Applications. The BE method produces a product with less than full density that can be as strong as wrought material, but that generally has lower ductility, toughness, and fatigue strength. Process modifications can improve these latter... 

The amount of flow before fracture determines the ductility of a polymer sample. In tough materials, a considerable amount of energy is dissipated by yield processes prior to fracture. In contrast, brittle samples break without showing much preceding flow. The difference becomes apparent in the fracture... 

The most commonly encountered impact modified plastic is high impact polystyrene (HIPS). The impact modification is achieved by incorporating discreet domains of a mbber (butadiene) within the polystyrene matrix. The level of butadiene can be varied according to the requirements of the end use. A high level can convert a glassy brittle material into a ductile, tough product. The efficiency of the butadiene to improve impact resistance alone is not solely related to concentration, but is also dependent on the size and... 

Unstable fast fracturing is not expected to occur from such fatigue crack because of ductile and tough material and low internal pressure. 

Toughness at 20°C is equal to =3.5 MPami, which is a respectable amount for a ceramic, but does not make alumina a tough material, especially when compared to metals. Ductility is modest. The coefficient of thermal expansion between 20°C and 1,000°C (0C20-1 000) 10" K b This relatively high thermal... 

Interlamellar connections are cmcial to the mechanical properties of polyethylene because they transmit forces between crystallites. Tie chains determine or influence a variety of mechanical properties, such as ductility, toughness, and modulus. Without the benefit of interlamellar links, polyethylene would be a brittle material with little physical strength. 

MCLCPs are tough materials and a benign failure is experienced on impact, similar to that exhibited by long-fibre-reinforced polymers or natural wood i.e. the failure is neither ductile nor brittle and the mouldings generally do not shatter. 

---