Nanjangud Subbarao Mohan

The present study aims to improve the tensile and hardness properties of carbon fabric–reinforced epoxy composite (CFEC) by using hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS₂) fillers. Magnetic stirring and ultrasonication were used to disperse fillers in epoxy resin. CFEC, h-BN filled CFEC and MoS₂ filled CFEC fabricated as per hand layup and vacuum bag technique. The tensile strength of CFEC was remarkably improved up to 6 wt.% h-BN and MoS₂ addition separately in the resin matrix. The maximum tensile strength of 486 MPa and Young’s modulus of 44 GPa were noticed in 6 wt.% h-BN incorporated CFEC displaying 59% and 47% improvements, respectively. The maximum toughness is shown by 6 wt.% MoS₂ incorporated CFEC indicating 102% improvement. The uniformly dispersed high-performance filler in the epoxy effectively transferred stress, improving tensile properties. However, filler agglomerates, stress-raising spots, and poor filler–matrix interaction beyond 6 wt.% filler reduced the tensile property improvement. The introduction of h-BN and MoS₂ in the composite increased hardness, with 6 wt.% h-BN added CFEC recording the highest hardness denoting 23% greater than the neat CFEC.

Carbon-fiber-reinforced epoxy composite (CEC) has gained widespread acceptance as a structural material in various applications. Drilled holes are essential for assembling composite material components. Reducing drilling-induced damage and temperature effects is crucial for improved surface quality and integrity of the drilled composite. In the present work, drilling experiments were conducted on CEC, hexagonal-boron nitride (h-BN) dispersed CEC, and molybdenum disulfide (MoS₂) dispersed CEC at three different levels of spindle speed, feed, and drill diameter using solid carbide twist drills. The filler concentrations used in this study were 4, 6, and 8 wt%. Analysis of variance (ANOVA) was used to determine the significance of input factors (feed, spindle speed, drill diameter, and filler concentration) on the drilling responses such as thrust force, temperature, arithmetic mean surface roughness (Ra), and push-out delamination factor (DFexit). The average drilling temperature, Ra, and DFexit of MoS₂ dispersed CEC were reduced by 24.7, 46.5, and 11.3%, respectively, when compared to neat CEC. In h-BN dispersed CEC, the average drilling temperature, Ra, and DFexit were reduced by 25.2, 40.9, and 13.2%, respectively, compared to neat CEC. The lubricating properties and high thermal conductivity of filler added to epoxy are responsible for the lower temperature and improved hole surface finish. The improved delamination resistance in filler-loaded CEC is due to the strengthening of the matrix and fiber–matrix interface. Scanning electron microscopy (SEM) was used to examine the morphology of the drilled composite surface. The spindle speed of 5500 rpm, feed of 0.03 mm.rev⁻¹, and filler loading of 4 wt% produced the minimum Ra and DFexit. The response surface method (RSM) was applied to determine the input parameters based on multi-response optimum criteria.

In the marine industry, glass fibers are commonly used to reinforce polyesters for ship hulls, submarine components, and other marine structures. Isophthalic polyesters are a feasible alternative due to their superior mechanical qualities and added end-of-life scenarios compared to orthophthalic polyesters. However, like other fiber composite systems, glass fiber reinforced polymer (GFRP) composites are also water sensitive. Here, GFRP composites of three different thicknesses are aged under three different immersion periods in seawater (20, 40 and 60 days). All samples are reconditioned and evaluated for hardness following aging. Significant emphasis is placed on the presence of calcium carbonate, over which increases in moisture content irrevocably reduce the composite’s hardness. Compared to untreated material, the hardness of 6, 8, and 10 mm composites decreased by 25.64, 10.92, and 4.63% after the 60-day aging period. This drop is mostly the result of microstructure evolution manifesting as an increase in porosity. Consequently, fiber deterioration, fiber cracks, and degradation of polymer-fiber bonding emerge in the composite, decreasing hardness.

This study aims at investigating the effect of water ageing on the durability of cellulose fibre reinforced polymer layered silicate nanocomposite. The material used comprises cellulose fibres from pinewood as reinforcement and high-density polyethene (HDPE) coupled with nanoclay as matrix phase. The prepared material is subjected to tap water ageing for 21 days. The durability is quantified by Barcol hardness for the material and measured at an interval period of 7 days. The obtained results indicate a reduction of hardness by 5.24, 13.17, and 16.60% in 7, 14, and 21 days aged nanocomposites. Besides, the one-way ANOVA test shows that the immersion time for the composite has a significant effect on the durability of the material with an R2 value of 99.96% tested at 95% confidence interval. The concluding remarks are validated using the results obtained for thickness swelling using the Fourier analysis. The work also presents a regression equation with high degree of accuracy, capable of estimating the Barcol hardness value for a given immersion time. ABSTRAK: Kajian ini bertujuan untuk mengkaji kesan penuaan air terhadap ketahanan nanokomposit silikat berlapis polimer bertetulang serat selulosa. Bahan yang digunakan terdiri daripada serat selulosa dari kayu pina sebagai tetulang dan polietena berketumpatan tinggi (HDPE) ditambah dengan nanoclay sebagai fasa matriks. Bahan yang disediakan mengalami penuaan air paip selama 21 hari. Ketahanan diukur dengan kekerasan bahan Barcol dan diukur pada selang waktu 7 hari. Hasil yang diperoleh menunjukkan penurunan kekerasan sebanyak 4.74, 8.88 dan 18.90% dalam nanokomposit usia 7, 14 dan 21 hari. Selain itu, analisis satu arah ujian varians menunjukkan bahawa masa rendaman komposit mempunyai pengaruh yang signifikan terhadap ketahanan bahan dengan nilai R2 99.96% yang diuji pada selang keyakinan 95%. Ucapan penutup disahkan menggunakan hasil yang diperoleh untuk pembengkakan ketebalan menggunakan analisis Fourier. Karya ini juga menyajikan persamaan regresi dengan tahap ketepatan yang tinggi, yang dapat menganggarkan nilai kekerasan Barcol untuk masa rendaman tertentu.

Fiber-reinforced polymer (FRP) composites are widely being used for structural applications due to their attractive properties. Particularly, to fabricate complicated structures by FRP composites, joining composite structure elements through fasteners require drilled holes. More than 60% of the structural FRP components are rejected owing to poor quality of holes. The FRP composites are heterogeneous due to multi-layer architecture, multi-phase material combinations, and hybridization. Hence, while drilling the behavior of FRP composites depends on various machining and tool parameters in addition to workpiece properties. As a result of drilling, the quality of drilled holes deteriorates due to delamination, matrix crack, matrix burning, fiber pull-out, buckling, spalling, and fuzzing in the drilled hole zone. To minimize all these defects researchers tried to design material, tool and machining parameters and reported. In this paper, the authors have made an attempt to summarize up-to-date progress in structure properties and drilling study of unidirectional and bidirectional multi-layered composites, three-dimensional fabric-reinforced composite and hybrid composite and similarly, emphasize the advanced characterization techniques to investigate the drilled hole quality. In addition, cryogenic assisted drilling, lubricated drilling, and micro-drilling literatures have been discussed. Based on the literature, conclusions and future scope have been reported.