Kalyan Kumar Singh

Impact of the carbon nanotube reinforcement in glass/epoxy polymeric nanocomposite on the quality of fiber laser drilling

In this work, the influence of multi-walled carbon nanotube is presented on laser drilling of multi-walled carbon nanotube–doped glass/epoxy polymeric nanocomposite. Multi-walled carbon nanotubes were dispersed in polymer matrix to improve the thermal conductivity and heat transfer characteristics of materials, which also reduces the divergence in decomposition temperature of matrix and glass fiber. Effect of carbon nanotube on laser drilling–induced damages was assessed by considering heat-affected zone, taper angle, and surface roughness as output parameters. Scanning acoustic microscopy showed the useful technique to examine the laser drilling damage around the hole by providing ply-by-ply damage analysis. In addition, scanning electron microscope provided more details to better analyze the machining quality of laser-drilled hole. Energy dispersive X-ray analysis provided the elemental analysis of charred material which is deposited on the hole wall. Obtained results indicate that the quality of hole was improved significantly due to addition of multi-walled carbon nanotube in polymer matrix.

Impact Response of Quasi-Isotropic Asymmetric Carbon Fabric/Epoxy Laminate Infused with MWCNTs

Effect of embedding multiwalled carbon nanotubes (MWCNTs) on low velocity impact response of quasi-isotropic asymmetric laminate of plain woven carbon fabric/epoxy was investigated. Laminates were embedded with 0u2009wt.%, 2u2009wt.%, and 5u2009wt.% MWCNTs to improve impact resistance. Impact in laminates was conducted according to ASTM D7136 standard at an impact energy of 94.14u2009J corresponding to the impact velocity of 6u2009m/sec. Energy-time response, force-time response, and pyramidal damage area of laminates doped with varying weight percentage (wt.%) of MWCNTs were quantified and compared with laminate without MWCNTs. Absorbed impact energy increases by 13.53% on doping of 2u2009wt.% MWCNTs, whereas it decreases by 10.49% on doping 5u2009wt.% MWCNTs. Damage area is reduced on doping 2u2009wt.% MWCNTs in laminate.

Tribological properties of Al 7075 alloy and Al 7075 metal matrix composite reinforced with SiC, sliding under dry, oil lubricated, and inert gas environments

Tribological properties of silicon carbide-based aluminum metal matrix composite and aluminum matrix alloy have been studied for various sliding speeds of 3.14 and 3.77u2009m/s and load range from 10 to 30u2009N under dry, lubricated, and inert gas (argon) environment. Pin-on-disk tribometer were used for experiments. The composite was fabricated by stir casting route by using aluminum 7075 alloy as the matrix and 10% by weight silicon carbide as reinforced material. Results have revealed that the value of coefficient of friction is found to be maximum in case of inert condition in matrix alloy at sliding speed 3.77u2009m/s and minimum in case of lubricated condition in composite at sliding speed 3.14u2009m/s. The wear rate is least for both the alloy and the composite under lubricated condition compared with dry and inert condition. Wear rate increases with the normal load and sliding speed and it is maximum in inert condition of matrix alloy at 30u2009N. Uniform distribution of silicon carbide in aluminum matrix alloy reduces the values of coefficient of friction and wear rate for composites compared to aluminum matrix alloy under dry, lubricated, and inert condition which increases the life of the composites for longer duration. Silicon carbide significantly improves the strength the aluminum matrix alloy in dry, lubricated, and inert condition and acts as load-bearing members.

Experimental investigation and modelling of drilling on multi-wall carbon nanotube–embedded epoxy/glass fabric polymeric nanocomposites

The primary objective of this research is to investigate the effect of multi-wall carbon nanotubes on drilling of multi-wall carbon nanotube–embedded epoxy/glass fabric polymeric nanocomposites. The experiments were conducted on composites with varying the weight percentage of multi-wall carbon nanotubes content to analyse drilling-induced delamination and surface roughness, which affect the quality and property of the drilled holes. The drilling parameters considered are spindle speed, feed rate and drill diameter. The microstructure of the holes was characterized using field emission scanning electron microscopy methods. For correlating the effect of the weight percentage of carbon nanotubes with the referred drilling parameters, a mathematical model was used, based on response surface methodology. For development of the mathematical model, four factors, namely, spindle speed, feed rate, diameter of drill and weight percentage of carbon nanotubes, were taken into account. The result established that delamination and surface roughness are reduced as multi-wall carbon nanotubes’ content increases. Maximum improvement in delamination factor was observed in the case of 1.0u2009wt% multi-wall carbon nanotube–embedded epoxy/glass fabric polymeric nanocomposite, which is 25% and 31.09% at the entrance and exit sides of the hole, respectively. With an increase in the feed rate and the drill diameter, delamination factor increases; however, with an increase in spindle speed, delamination factor decreases. Lower value of surface roughness (1.113u2009µm) was observed in 1.5u2009wt% of multi-wall carbon nanotube–embedded epoxy/glass fabric polymeric nanocomposite. However, surface roughness increases with an increase in feed rate and drill diameter.

A strategy for enhancing shear strength and bending strength of FRP laminate using MWCNTs

Multi-wall carbon nanotubes (MWCNTs) promises to enhance mechanical properties exceptionally when it is doped with fiber reinforced polymer (FRP) composite. Glass fiber symmetrical laminate with eight layers of 4.0 mm thickness was fabricated by hand lay-up technique assisted by vacuum bagging method. Ply orientations for symmetrical laminate used [(0,90)/(+45,-45)/(+45,-45)/(0,90)//(90,0)/(+45,-45)/(+45,-45)/(90,0)]. MWCNTs reinforced three different samples (0 wt.%, 0.5 wt.% and 0.75 wt.% by weight) were tested on universal testing machine (UTM). Short beam strength test and inter laminar shear strength (ILSS) calculation have been done according to ASTM D2344 and ASTM D7264. UTM having maximum load capacity of 50 KN with loading rate of 0.1 mm/min to 50 mm/min was used for mechanical testing. Testing results justified that by adding 0.50 wt.% MWCNTs in symmetrical GFRP laminate can enhance inter laminar shear strength by 13.66% and bending strength by 44.22%.

Effectiveness of short and straight carbon nanotubes on dispersion state and static/dynamic mechanical properties of woven glass fibre-reinforced polymer laminates

This study reports about the dispersibility of short, straight and pristine multi-walled carbon nanotubes (pCNTs) in epoxy and their effectiveness on the mechanical properties of three-phased GF/epoxy/pCNT laminates. These nanotubes were produced by arc discharge method and had an average aspect ratio (l/d) of 100. Glass fibre-reinforced polymer samples with four different weight fractions of these nanotubes (0.5, 1.0, 1.5 and 2.0u2009wt.% of the total matrix system) were fabricated and tested for their thermo-mechanical and mechanical properties. These carbon nanotubes with small aspect ratio contributed well to the strengthening mechanism due to their homogeneous dispersion. Fractography revealed that these nanotubes formed aligned arrays that minimized entanglements between the individual tubes, thus leading to lesser agglomerates up to 1.5u2009wt.% of carbon nanotube loading. However, the samples modified with 2.0u2009wt.% of nanotubes had lesser individual tubes and more of their aggregates. Unmodified glass fibre-reinforced polymer samples had a glass transition temperature (Tg) of 139.2℃, whereas addition of 1.5u2009wt.% of multi-walled carbon nanotubes increased the same to 160℃. Similarly, these specimens witnessed about 21% and 34% enhancement in tensile and flexure strength over the control samples, respectively. However, these trends dropped at 2.0u2009wt.% carbon nanotube loading owing to nanotubes aggregation but were higher than those of the neat epoxy composite. Samples containing carbon nanotubes witnessed higher fatigue life which proves that multi-walled carbon nanotubes with smaller aspect ratio are capable of obstructing fatigue crack growth.

Fatigue damage analysis of fiber-reinforced polymer composites—A review:

Fiber-reinforced polymer composites are becoming suitable and substantial materials in the repair and replacement of conventional metallic materials because of their high strength and stiffness. These composites undergo various types of static and fatigue loads during service. One of the major tests that conventional and composite materials have to experience is fatigue test. It refers to the testing for the cyclic behavior of materials. Composite materials are different from metals, as they indicate a distinct behavior under fatigue loading. The fatigue damage and failure mechanisms are more intricate in composite materials than in metals in which a crack initiates and propagates up to fracture. In composite materials, several micro-cracks initiate at the primary stage of the fatigue growth, resulting in the initiation of various types of fatigue damage. Fiber volume fraction is an important parameter to describe a composite laminate. The fatigue strength increases with the increase of the fiber volume fraction to a certain level and then decreases because of the lack of enough resin to grip the fibers. The fatigue behavior of fiber-reinforced polymer composites depends on various factors, e.g., constituent materials, manufacturing process, hysteresis heating, fiber orientation, type of loading, interface properties, frequency, mean stress, environment. This review paper explores the effects of various parameters like fiber type, fiber orientation, fiber volume fraction, etc. on the fatigue behavior of fiber-reinforced polymer composites.

Investigation of delamination and surface quality of machined holes in drilling of multiwalled carbon nanotube doped epoxy/carbon fiber reinforced polymer nanocomposite:

In the drilling of carbon fiber reinforced polymer composite materials, drilling-induced delamination and surface roughness of machined holes are causes of major concern, particularly, when components, made of carbon fiber reinforced polymer, are used in the aerospace industry. In order to minimize these drawbacks, an innovative technique has been developed by adding multiwalled carbon nanotube in the polymer matrix to improve interlaminar shear strength and flexural strength of the laminates. Experimental results indicate that with this process, flexural strength and interlaminar shear strength get enhanced by almost 24% and 28%, respectively, when compared to neat epoxy carbon fiber reinforced polymer composite. The image process results reveal that delamination factor gets decreased by 21% and 28.60% at the entrance and the exit side, respectively. This, in turn, not only reduces the delamination factor during the process but also facilitates the process to be carried out more smoothly. During this investigation, scanning acoustic microscope was used to study ply-by-ply damage followed by ultrasonic C-scan on both sides of the laminates, which showed good agreement with the experimental results. Measurement of surface roughness of the machined hole showed the maximum Ra value of 5.03u2009µm in neat epoxy carbon fiber reinforced polymer composite. However, a sample with 1.5u2009wt% of multiwalled carbon nanotube showed a decline in Ra value (1.18u2009µm). Thus, addition of multiwalled carbon nanotube to the polymer matrix could reduce the drilling-induced delamination as well as the surface roughness of machined hole simultaneously.