Mechanical and Ballistic Resistance Properties of a Coconut Shell Powder Epoxy Composite (Coex) Subjected to Impact Loads

An armor design study has been carried out to determine the feasibility of utilizing a coconut shell powder (CSP) reinforced composite as one of the protective component in hard body armor application. Few experimental approaches have been carried out to determine the physical and mechanical properties of coconut shell powder-epoxy composite (COEX). The COEX composite panel bonded with Twaron CT716 fabric as its spall liner (or COMBAT) was also subjected to ballistic tests at several impacting velocity in order to determine the COEX armor ballistic resistance capabilities at certain threat levels. The physical properties of CSP-A (coarse grade) with low aspect ratio of 0.71, bulk density of 0.424 g/cm3 and broad particle size distribution were important factors in the its selection as the best powder type for COEX specimen fabrication. This was due to its potential influences (based from the properties) of increasing the particle-matrix interfacial bonding in the COEX composite system. CSP-B (fine grade) and CSP-C (super fine grade) although possessing higher bulk density which can lead to better compaction, were not chosen due to its higher moisture content and aspect ratio. where these properties is expected to give a weak interfacial bonding for the composite system. These statements was proven in the mechanical testing (tensile, flexural, compression and hardness), where COEX-A (with CSP content of 50%) imparts the highest value in all mechanical properties. It had been found that the tensile, compressive and flexural strength of COEX-A was measured at 17.44 MPa, 100.05 MPa and 194.8 MPa respectively when compared to the other COEX configurations. The Rockwell hardness value for COEX-A was also found to be the highest compared to COEX-B and COEX-C. All these mechanical properties play a significant influence in the ballistic resistance capabilities of the COEX materials Statistical models were developed using 2 level of Full Factorial Design method to predict the armor‟s impact resistance and blunt trauma depth using several parameters which are critical to the fabrication and ballistic testing of the COMBAT armor panel. The models were verified and showed good agreement with the actual laboratory test data. Finally, the for actual ballistic armor test of the COMBAT armor panels were tested according to NIJ Standard 0101.08 with 9 mm Full Metal jacket and 7.52 mm M-16 bullets. It was observed that the imprint patterns on the COEX materials could be identified according to the effectiveness in impact energy dissipation. COMBAT test panels were found to withstand impact equivalent to NIJ Level IIIA using a 9 mm FMJ ammunition but perforated at NIJ Level III of 7.62 mm FMJ bullet impacts. Test results showed that COEX panel do possess shock absorbance characteristics and can be utilized as an armor component in the hard body armor system. Dependency on the numbers of Twaron fabric layers as ballistic reinforcements had been reduced up to 3 times with 170 % improvement on energy absorption capabilities when using COEX composite as the frontal component of the armor

Experimental Damage Investigation of Composite Plates Subjected to Impact Loading Conditions

The use of synthetic fibers such as glass fiber and aramid fiber carbon fiber as composite reinforcement is being increasingly applied in high performance applications since they provide certain advantage of specific high strength and stiffness as compared to metallic materials. In contrast, implementation of natural fiber as reinforcement has not yet received adequate attention from the research community. This study investigates the damage characterization and impact resistance of synthetic and natural fiber reinforced composite square plates subjected to the changes of impact loading and width over thickness (bId) ratio of the composite. For low velocity impact, the testing was performed using Dynatup 8250 equipped with GRC 930-1 Data Interpretation System on fabricated square plates with different impact energy levels and velocities. The severity of impact damage is macroscopically and microscopically investigated. A compressed gas gun equipped with velocity measurement system was designed and fabricated in order to facilitate the high velocity impact testing experimentations. From the results, it has been found that mechanical and impact properties of EFBC and CFC do not posses toughness and modulus as high as GRC. Although EFBC and CFC specimens eXllibit total perforation to the specimens at most impact velocities, EFBC specimen with plate thickness of 8 millimetres was found to have penetration resistance at 22 joules of impact energy level. This is due the performance of Coir as reinforcement in polymer composites is unsatisfactory and not comparable with other natural fibers due to its mechanical properties. It can also be conclude that the impact response of EFBC and CFC specimen chances significantly as the composite thickness increases. Impact damage was found to be in the forms of matrix cracking, fiber fracture and perforation. This study results can be a valuable reference in designing of lightweight composite structure and in developing a better understanding of test methods used to characterize impact behaviours

Improvement of energy absorption on magnesium alloy mixed carbon-nanotube and lead reinforcement materials in terms of high velocity impact

This paper presents the fracture behaviour of magnesium alloy (AZ31B) with the reinforcement of carbon-nanotube (CNT) and lead subjected ballistic impact. Magnesium alloys are material that can absorb impact energy, however the absorption energy can be increased with the alloy reinforcement with nano-partial. This paper leads to two parts which are experiment and simulation of gas gun. The projectile used was a cone-nose type with diameter of 11 mm made by steel series 1006. The simulation used Cowper-Symonds model to see material behaviour with 25 mm thickness. The correlation of the experiment and simulations was evaluated to see the accuracy of simulations made. It was shown that the value of R2 was 0.9588 where simulation can be used to predict the ballistic impact on 600 m/s velocity. From the simulation results, it was found that the depth of penetration for Magnesium alloy AZ31B reinforced with CNT and Pb showed good agreement findings. The depth of penetrations onto the simulation were obtained between 15 to 25 mm. The added reinforcement materials provide a reduction in the depth of penetration of 40% compared to the original Magnesium alloy AZ31B. Thus, this type of magnesium alloy reinforced with CNT and Pb is suitable for ballistic resistant panel with weight saving determination on armoured vehicle.Â

Performance of Hybrid Steel Fibers Reinforced Concrete Subjected to Air Blast Loading

This paper presents the results of the experimental data and simulation on the performance of hybrid steel fiber reinforced concrete (HSFRC) and also normal reinforced concrete (NRC) subjected to air blast loading. HSFRC concrete mix consists of a combination of 70% long steel hook end fibre and also 30% of short steel hook end fibre with a volume fraction of 1.5% mix. A total of six concrete panels were subjected to air blast using plastic explosive (PE4) weighing 1 kg each at standoff distance of 0.3 meter. The parameters measured are mode of failure under static and blast loading and also peak overpressure that resulted from detonation using high speed data acquisition system. In addition to this simulation work using AUTODYN was carried out and validated using experimental data. The experimental results indicate that hybrid steel fiber reinforced concrete panel (HSFRC) possesses excellent resistance to air blast loading as compared to normal reinforced concrete (NRC) panel. The simulation results were also found to be close with experimental data. Therefore the results have been validated using experimental data

Failure observation of the AZ31B magnesium alloy and the effect of lead addition content under ballistic impact

The association of the failure behavior of the AZ31B magnesium alloy with absorption energy under ballistic impact condition was investigated in this study, as well as the effect of varying percentages of added lead (Pb) content. The compositions of Pb in AZ31B were 1%, 5%, and 10% by percentage weight of Pb. Two types of projectile were used to compare the experimental and simulation results. Ballistic testing on a magnesium alloy plate was performed at the velocity of 435 m/s for the 9 mm×19 mm Parabellum projectile and 976 m/s for the 5.56 mm×45 mm NATO projectile. Simulation was performed using the Johnson–Cook model to determine the maximum stress that the material can withstand. Deformation and failure occurred in the ballistic simulation when the different projectiles were used. In the 9 mm×19 mm Parabellum projectile, no penetration was observed in the magnesium alloy, whereas in the 5.56 mm×45 mm NATO projectile, complete penetration was observed throughout the thickness of the alloy. The addition of Pb on AZ31B affected the absorption energy, and the addition of 1% Pb produced the most suitable absorption energy for further analysis

The effect of surfactant on stability and thermal conductivity of carbon nanotube based nanofluids

The addition of highly conductive substance such as carbon nanotubes into a traditional heat transfer fluid will enhance the fluids’ thermal conductivity. However, dispersion process of carbon nanotubes into base fluids is not an easy task due to hydrophobic characteristic of its surface. This study attempts to investigate the stability and thermal conductivity of carbon nanotube based ethylene glycol/water nanofluids with and without surfactants. Stability investigation was conducted through observation and zeta potential measurement methods. As for the thermal conductivity, the samples were measured based on transient line heat source. The results showed that 0.01 wt.% of carbon nanotube based nanofluid, containing 0.01wt.% hexadecyltrimethylammonium bromide possess highest zeta potential value compared to the other tested samples. 0.5 wt. % of carbon nanotube based nanofluids with gum arabic exhibit 25.7% thermal conductivity enhancement

Comparative Study on Extraction of Cellulose Fiber from Rice Straw Waste from Chemo-Mechanical and Pulping Method

Inspired by nature, cellulose extracted from plant wastes has been explored, due to its great potential as an alternative for synthetic fiber and filler that contributes to structural performance. The drive of this study was to extract, treat, and evaluate the characteristics of rice straw (RS) (Oryza sativa L.) cellulose as a biodegradable reinforcement to be utilized in polymer base materials. Two routes of extraction and treatment were performed via the pulping (Route 1) and chemo-mechanical methods (Route 2), in order to discover comparative characteristics of the synthesized cellulose fiber. Comprehensive characterization of RS cellulose was carried out to determine crystallinity, surface morphology, and chemical bonding properties, using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infra-red (FTIR), respectively. The XRD test results showed that the crystallinity index (CI) of cellulose powder (CP) decreased after the surface modification treatment, Route 2, from 64.50 to 50.10% CI for modified cellulose powder (MCP), due to the surface alteration of cellulose structure. From Route 1, the crystallinity of the fibers decreased up to 33.5% (dissolve cellulose, DC) after the pulp went through the surface modification and dissolution processes, resulting from the transformation of cellulose phase into para-crystalline structure. FESEM micrographs displayed a significant reduction of raw RS diameter from 7.78 µm to 3.34 µm (treated by Route 1) and 1.06 µm (treated by Route 2). The extracted and treated cellulose via both routes, which was considerably dominated by cellulose II because of the high percentage of alkaline used, include the dissolve cellulose (DC). The dissolution process, using NMMO solvent, was performed on the pulp fiber produced by Route 1. The fiber change from cellulose I to cellulose II after undergoes the process. Thus, the dissolution process maintains cellulose II but turned the pulp to the cellulose solution. The acquired characteristics of cellulose from RS waste, extracted by the employed methods, have a considerably greater potential for further application in numerous industries. It was concluded that the great achievement of extracted RS is obtained the nanosized fibers after surface modification treatment, which is very useful for filler in structural composite applications