Increasing the ductility

As already mentioned in section 8.4.2, the ductility of semi-crystalline thermoplastics is increased if they are used above their glass temperature. Here, the amorphous regions are easily deformable, whereas the crystalline regions increase the strength. Semi-crystaUine thermoplastics are thus well-suited for applications requiring an increased ductility. 

Copolymerisation is another approach to improve the mechanical behaviour of polymers, especially their ductility. In copolymerisation, different monomers are used to form the chain molecules. There are several possibilities to arrange the monomers, shown in figure 8.26. The monomers can alternate alternating copolymerisation) or can be arranged irregularly random copolymerisation). In block copolymers, there are longer chain segments of one type 

Copolymerisation is frequently used to decrease the glass temperature, with the intent of increasing the ductility. This is called internal plasticisa- 

Block copolymers can also increase the ductility by affecting cra.zing. As explained in section 8.4.1, crazes in amorphous polymers are initiated at surface defects because cavities can form there more easily. These cra.zes 

Plasticisers are molecules added to a polymer to reduce its glass temperature and thus increase its ductility. 

---

Several flexible polymers, such as natural rubber (NR) synthetic rubber (SR) polyalkyl acrylates copolymers of acrylonitrile, butadiene, and styrene, (ABS) and polyvinyl alkyl ethers, have been used to improve the impact resistance of PS and PVC. PS and copolymers of ethylene and propylene have been used to increase the ductility of polyphenylene oxide (PPO) and nylon 66, respectively. The mechanical properties of several other engineering plastics have been improved by blending them with thermoplastics. 

The ether linkages in PEI improve the ease of processing and increase the ductility of these high performance plastics.(Ji)... 

Formation of the martensitic phase and strain-induced transformation of austenite to martensite increases the susceptibility of 304 stainless steel to HE [182,183]. In the presence of hydrogen, more transformed martensite is formed, increasing the ductile loss of the material [184]. Caskey [185] observed that large grain sizes deteriorate the FS of austenitic stainless steel due to the presence of hydrogen. Tsay et al. [186] evaluated the... 

Figure 7 shows clearly the effect of number of joints on strength and deformation behaviour of POP specimen under unconfined condition. The strength decreases drastically and further the strain at failure increases. It can be seen that, as the joint frequency increases, the ductile nature of the specimen is more pronounced and atransition between brittle to ductile behaviour is observed from intact to specimen with three joints (Figure 7). The reduction in the strength for one joint at P=90° i.e., 13 joints per meter, is around 10% (Figure 7). The reduction is around 30% and 40% for 26 joints and 39 joints per meter respectively. Although the strength decreases with an increase in the number of joints, failure modes are almost similar for a specific inclination and the crack propagation usually interrupted due to the presence of discontinuity. Similar observation was reported by Arora (1987) and the reduction of strength was aroimd 7% for 10 joints per meter...

The test beam s destroying process of L2, L3 are similar with LI, but with the increase of reinforcement ratio, the stiffness of the test beam increased. The ductility descend. The way that the test beam destroyed gradually develop in the direction of brittle failure. The damage of L3 in compressive zone of concrete happened suddenly. It s a kind of instantaneous burst, along with the noise. The main characteristics of the load shown in Table 3. 

Ceramic materials are commonly brittle materials with varying degrees of brittleness. The aim of this research is to increase the ductility of HPSN ceramic materials by the aid of laser preheating process and in process. With this method, it will be possible to increase the depth of cut (productivity of the process) more than 20 times and at the same time, keep the process in the ductile mode (free of surface and subsurface damages). 

This research is unique in that the grinding system will be considered as a thermal-tribo system and the laser energy and friction energy together will provide indications for the necessary energy for increasing the ductility of HPSN ceramic materials. 

The nanocomposites in general possess better fracture toughness and impact strength than neat epoxy. However, the water treatment increased the fracture toughness and the impact strength significantly. The water treatment also increased the ductility of the epoxy matrix by... 

Poly (hexamethylene adipimide) is also known as Nylon 6,6 since its repeat unit has two six-caibon sequences. Nylon is tough, abrasion resistant, and has a low coefficient of friction, making it a popular suture material. Nylon 6,6 is hydrophilic and absorbs water when placed in tissues or in humid environments (9 to 11 percent water when fully saturated ). Absorbed water acts as a plasticiser, increasing the ductility and reducing the modulus of Nylon 6,6. Nylon bioerodes at a very slow rate. Nylon 6,6 implant in dogs lost 25 percent of its tensile strength after 89 days and 83 percent after 725 days. ... 

As much as 30% of all polyolefin products involve blends (Robeson 2007). It has been found, for example, that blending metallocene-catalyzed linear low-density polyethylenes (mLDPEs) with HDPE improves the Izod impact strength and some tensile properties of HDPE. Adding mLLDPE to LDPE increases the ductility of LDPE (Cran and Bigger 2009). In general, PE blends can be divided into three categories (1) PE lots blended to meet standard specifications for density and melt flow, (2) PE modified with <15 wt% of other polymer(s), and (3) PE bends with other thermoplastics or thermoplastic elastomers. 

The main role of fibres is to bridge the cracks that develop in concrete and increase the ductility of concrete elements. Fibres increase the strain at peak load, as well as provide additional energy absorption ability of reinforced concrete elements and stractures. It was recently reported that they also considerably improve the static flexural strength of concrete as well as its impact strength, tensile strength, ductility and flexural toughness (Shah and Ribakov, 2011 Pacheco-Torgal and Jalali, 2011). 

Figure 8 shows the time history response of the horizontal displacement of the upper beam-column joint. A reduction of approximately 40% is obtained for the maximum lateral displacement when compared with the bare frame. Acceleration and velocity are controlled in the same way, but only 10 and 5 % of reduction is obtained. A possible explanation for the limited effectiveness of the EDD is that the devices only contribute to increase the ductility of the beam-column joint without alleviating the base shear demand on the columns due to the dimensions of the device and its location in the structure. By other hand, joints are critical points in precast structures and therefore, the employment of EDDs combined with a careful design of the columns can help to improve their seismic behavior. 

Addition of 30 wt% PEG to PLA with low stereoregularity decreases 7g from above ambient temperature to below ambient temperature and thereby decreases the modulus and increases the ductility of this relatively rigid, brittle thermoplastic. Immediately after cooling from the melt, blends with up to 30 wt% PEG are amorphous and homogeneous with a single Tg that depends on composition in accordance with the Fox relationship. However, the blends with 20 wt% or more PEG are not stable at ambient temperature. 

---