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.

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.

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.

The use of carbon fiber reinforced plastic (CFRP) is increasing in engineering applications such as aerospace, automobiles, defense, and construction. Excellent strength-to-weight ratio, high impact toughness, and corrosion resistance make CFRP highly suitable for aerospace applications. Curing temperature, curing time, and autoclave pressure are among the most important curing parameters affecting the properties of CFRP. Tensile strength, impact toughness, and hardness of CFRP were selected as desirable properties for optimization. A 2³ full factorial design of experiment (DOE) was employed by varying curing temperature (120 and 140 °C), curing time (90 and 120 min), and autoclave pressure (3 and 7 bar) while keeping the number of experiments to a minimum level. The cured samples were subjected to tensile strength, impact toughness, and hardness tests at room temperature as per relevant ASTM standards. Analysis of variance (ANOVA) was used, and it was found that tensile strength, impact toughness, and hardness were influenced most significantly by temperature and time. The maximum tensile strength and hardness were achieved for curing cycle parameters of 140 °C, 120 min, and 7 bar, and impact toughness was maximized for 140 °C, 120 min, and 3 bar. A concept of composite desirability function was used to achieve simultaneous optimization of conflicting tensile strength and impact toughness properties for the specific application of aircraft skin.