Browsing by Author "Gowda, D."

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An Optimization Study on Material Selection for FRPCs in Multi Layered Armour System through Hybrid MCDM Approach and Numerical Simulation
(Syscom 18 SRL, 2022) Gowda, D.; Bhat, R.; Rajole, S.
Fiber reinforced polymer composites (FRPCs) are considered as core structure in Multi layered armour systems (MAS) to take advantage of maximum energy absorption, mobility and cost criteria design. In this article, based on the problem defining attribute’s optimal material selection in FRPCs determined by Multiple criteria decisions making (MCDM) approach for considered alternative materials from polymer resin, synthetic and natural fiber. Attribute’s weightage and alternatives priority rank were determined through Fussy-Analytical hierarchy process (F-AHP) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method. Obtained rank was compared with Preference selection index (PSI) an another MCDM method, for better computational conformity. Selected materials from MCDM approach, simulated for energy absorption ability and damage after impact were studied by considering Cowper-Symonds constitutive materials model using 3D macro shell analysis. Various impact velocities were considered from 3 to 50 m/s for rigid steel impactor directed towards the deformable plate. Parameter like Residual kinetic energy, Residual velocity, Energy absorption ratio after impact were studied numerically. Simulation results in terms of specific energy absorption were compared with the rank obtained in MCDM approach. Among the polymers considered epoxy, polyurethane and polyester found better choice. In fibers hemp and basalt found better materials choice for heterogenous FRPCs design in ballistic armour. © 2022 Syscom 18 SRL. All rights reserved.
Bio-inspired helicoidal hemp/basalt/polyurethane rubber bio-composites: Experimental, numerical and analytical ballistic impact study with residual velocity prediction using artificial neural network
(Elsevier B.V., 2024) Gowda, D.; Bhat, R.S.
Recent body armour trends emphasize mobility, flexibility, and cost reduction while maintaining ballistic effectiveness through the use of natural fiber composite. This study evaluates the ballistic impact performance of soft and hard armor using experimental, analytical, numerical, and machine learning methods. We developed a soft armor bio-composite using monolithic, hybrid, and helicoidal structured Hemp (H)/Basalt (B)/Polyurethane (PU) rubber and tested its V50 ballistic limit according to Millitary-Standred-662 F. For hard armour, a multi-layer armor system (MAS) consisting of Al2O3/SiC ceramic, intermediate soft armour bio-composites, and an Aluminum (Al)-5052 plate backing was tested with armour-piercing bullets as per National Institute of Justice (NIJ)-0101.06 standards (Level IV). Soft armor performance was evaluated using macro-homogeneous finite element (FE), the Ipson-Retch analytical, and an Artificial Neural Network (ANN) regression model. Results showed minimal discrepancies from experimental data, with differences of 13.33 %, 12.08 %, and 8.08 % in V50 ballistic limit. The mechanical and thermal behaviors of bio-composites were assessed using un-notched Charpy, FTIR, and TGA methods. Helicoidal laminates improved Charpy toughness by 9.44 %, 19.30 %, and 40.28 % compared to hybrid and monolithic ([H]15 and [H]10) laminates, and exhibited lower weight reduction at high degradation temperature of 395.76 ?. Helicoidal laminates increased V50 ballistic performance by 155.80 %, 76.22 %, and 16.61 % compared to [H]10, [H]15, and hybrid laminates, respectively. Due to spiral load distribution reduces stress concentration and enhanced the damage resistance of the laminate. Stand-alone soft armor demonstrates crater formation and radial cracks (petaling) due to fiber wedging and the shearing effect of a bullet. In conclusion, MAS revels a maximum back face deformation (BFD) of 18.06 mm. Al2O3/Helicoidal/Al-plate MAS reduced weight and cost by 69.21 %, and 233.72 % compared to Kevlar™-based MAS, promoting sustainable, lightweight, economical designs. Due to its higher fracture toughness and lower density, SiC ceramic in MAS provides lower trauma and further reduced weight compared to Al2O3 ceramic. © 2024 Elsevier B.V.
Experimentation on dynamic compressive response of bio-inspired helicoidal structured Basalt/Hemp/polyurethane rubber sandwich composites
(Elsevier Ltd, 2024) Gowda, D.; Mahesh, V.; Mahesh, V.; Ravishankar, K.S.
In this article, to incorporate sustainability, enhance recyclability and achieve a good trade-off between the cost-weight-energy absorption performance, bioinspired helicoidal structured Basalt (B)/Hemp (H)/Polyurethane (PU) rubber hybrid composites are proposed, and their dynamic compressive response is experimentally investigated using a split Hopkinson pressure bar (SHPB) setup. These composites' high strain rate performance subjected to both in-plane and through-plane directions are studied. The strain rates ranging from 4254 to 10,750 s-1 are achieved by varying the striker bar's input pressure. In addition, the performance of the bioinspired helicoidal design is compared against the uniform monolithic and hybridised fibers laminated structures. The experimental results suggest that the dynamic compressive properties of Basalt/Hemp-helicoidal (BH-helicoidal) laminates were on compar with that of B-laminates, achieving an almost 30% weight reduction. The optimised fiber orientation at a helical angle of 120 enhances interlaminar shear strength, mitigating buckling and delamination failures, thereby improving BH-helicoidal laminate's structural integrity and dynamic compressive properties. Further, the through-plane dynamically loaded samples displayed better compressive properties due to increased stiffness than in-plane samples. The PU rubber matrix was thermally softened at higher strain rates, enhancing the flow stress. The strengthening mechanism of the proposed composites was evaluated through Cowper-Symonds, strain rate sensitivity, and thermal activation volume parameter. Macroscopic and microscopic imaging was proposed to understand the damage behaviour of laminates as a function of loading direction. Overall, BH-helicoidal laminate is favoured for ballistic application due to its cost-effectiveness and sustainable design. © 2024 Elsevier Ltd
Low-velocity impact characterization of polyurethane rubber/nano-clay enriched sustainable sandwich composites: Synergy of experimentation and simulations
(John Wiley and Sons Inc, 2024) Gowda, D.; Mahesh, V.; Mahesh, V.; Ravishankar, K.S.
This research proposes a novel sustainable composite using basalt (B), hemp (H) and polyurethane rubber (Pu) reinforced in nano clay functionalised epoxy matrix for sacrificial structural applications prone to low-velocity impact (LVI). To this end, symmetric and asymmetric laminates such as HHHH, BBBB, BHHB, BHPuHB, BBPuHH and BPuBPuHPuH are fabricated using compression molding techniques and subjected to LVI at three different impact energies of 19.66, 39.39, and 59.05 J. The hemp fibers were treated with NaOH solution before fabrication. Material characterization such as X-ray diffraction, Raman spectroscopy and morphological studies has been carried out. The impact and post-impact properties of the proposed composites are experimentally evaluated and validated with the finite element (FE) results. The effect on the residual tensile strength degradation of laminates at different interlayers and energy levels is also investigated using the Caprino analytical model. The barely visible impact damages (BVID) are investigated through non-destructive dye-penetration tests, which facilitate easy identification of the prominent LVI damages like “Plateau” and “Cliff-drop” impressions. Based on the impact energy absorption and residual tensile strength, proposed laminates followed BHPuHB > BBBB > BHHB > HHHH. The experimentation suggests that Polyurethane core laminates support maximum impact energy absorption by favoring a structural change in interlayers. Also, the residual tensile strength decreases as impact velocity increases. Highlights: Low-velocity impact behavior of sustainable composites is experimented. Basalt, hemp and polyurethane rubber are reinforced in nano clay epoxy matrix. A FE framework to validate the experimentation is proposed. Dye penetrant NDT is adopted to investigate the damages. Morphological studies are conducted to understand LVI responses. © 2024 Society of Plastics Engineers.