Polyamide-6-based composites with pristine or functionalized multi-walled carbon nanotubes were produced using melt extrusion technique. After chemical functionalization, defect formation and attachment of carboxylic (−COOH) or amine (−NH2) groups on carbon nanotubes was confirmed from high-resolution transmission electron microscope and Fourier transform infra-red spectroscope studies. Carbon nanotubes incorporation promoted growth of α-form crystals with enhanced thermal stability through increase in crystallization temperature from 162 to 192℃. Dynamic mechanical thermal analysis (DMTA) indirectly pointed out to a homogeneous, uniform dispersion of nanotubes with reduction in free volume of the polymer, exhibiting a slight increase in glass transition temperature and a significant drop in coefficient of thermal expansion value. Composites containing 0.5 wt% NH2-carbon nanotubes show increases in elastic modulus and tensile strength by ∼60 and 76%, respectively. Uniform dispersion and high interfacial strength was manifested by drop in strain to failure and lack of evidence of carbon nanotubes debonding from the matrix.

Pure polyamide 6 (PA6) and polyamide 6/carbon nanotube (PA6/CNT) composite samples with 0.5 weight percent loading of pristine or functionalized CNTs were made using a solution mixing technique. Modification of nanotube surface as a result of chemical functionalization was confirmed through the presence of lattice defects as examined under high-resolution transmission electron microscope and absorption bands characteristic of carboxylic, sulfonic and amine chemical groups. Microstructural examination of the cryogenically fractured surfaces revealed qualitative information regarding CNT dispersion within PA6 matrix and interfacial strength. X-ray diffraction studies indicated formation of thermodynamically more stable α-phase crystals. Thermogravimetric analysis revealed that CNT incorporation delayed onset of thermal degradation by as much as 70 °C in case of amine-functionalized CNTs, thus increasing thermal stability of the composites. Furthermore, addition of amine-functionalized CNTs caused an increase in crystallization and melting temperatures from the respective values of 177 and 213 °C (for neat PA6) to 211 and 230 °C (for composite), respectively.

In this study, the effects of functionalization and weight fraction of mutliwalled carbon nanotubes (CNTs) were investigated on mechanical and thermomechanical properties of CNT/Epoxy composite. Epoxy resin was used as matrix material with pristine-, COOH-, and NH 2 -functionalized CNTs as reinforcements in weight fractions of 0.1, 0.5, and 1.0%. Varying (increasing) the weight fraction and changing type (pristine or functionalized) of CNTs caused increment in Young's modulus and tensile strength as observed during mechanical tests. CNT reinforcement improved thermal stability of the nanocomposites as observed by thermogravimetric analysis. Thermomechanical analysis showed a slight reduction in free volume of the polymer, that is a drop in coefficient of thermal expansion, prior to glass transition temperature (T g ) beside a slight increase in T g value. Dynamic mechani-cal analysis indicated an increase in storage modulus and T g owing to the strength addition of CNT to the matrix alongside the hardener. Scanning electron microscopy analysis of the fractured surface(s) revealed that CNTs were well dispersed with no agglomeration and resulted in reinforcing the matrix. POLYMER COMPOSITES-2015 FIG. 4. Dimensional change as a function of temperature for pure epoxy and different epoxy/CNT composites. FIG. 5. DMA studies of neat epoxy and different CNT/E composites for a range of temperatures at 1.0 Hz frequency and 5 C/min heating rate: (a) storage modulus and (b) dissipation factor (tan d).FIG. 3. TGA weight loss data over a range of temperatures for neat epoxy and nanocomposite samples.

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Roll bonding (RB) describes solid-state manufacturing processes where cold or hot rolling of plates or sheet metal is carried out for joining similar and dissimilar materials through the principle of severe plastic deformation. This review covers the mechanics of RB processes, identifies the key process parameters, and provides a detailed discussion on their scientific and/or engineering aspects, which influence the microstructure–mechanical behavior relations of processed materials. It further evaluates the available research focused on improving the metallurgical and mechanical behavior of bonded materials such as microstructure modification, strength enhancement, local mechanical properties, and corrosion and electrical resistance evolution. Moreover, current applications and advantages, limitations of the process and developments in dissimilar material hot roll bonding technologies for producing titanium to steel and stainless steel to carbon steel ultra-thick plates are also discussed. The paper concludes by deliberating on the bonding mechanisms, engineering guidelines and process–property–structure relationships, and recommending probable areas for future research.