Faculty Publications
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Item Effect of similar and dissimilar interface layers on delamination in hybrid plain woven glass/carbon epoxy laminated composite double cantilever beam under Mode-I loading(Elsevier B.V., 2021) Suman, M.L.J.; Murigendrappa, S.M.; Kattimani, S.Effect of similar and dissimilar interface layers on delamination in hybrid plain woven glass/carbon epoxy laminated composite double cantilever beam under Mode-I loading has been investigated experimentally and analytically. Glass-glass, glass-carbon interface layers in three different configurations of hybrid plain woven glass/carbon epoxy laminated composites were fabricated. Valvo's mode partition method from the literature is utilised to compute individual modal contributions and total fracture toughness of the hybrid composite laminates. Mode-I fracture toughness contribution is compared with standard data reduction schemes of ASTM D5528-13. The comparison reveals that Valvo's mode partition method considers mode-mixity and provides conservative results. The Valvo's mode partition does not require any correction factors including curve fitting, it provides a straightforward method for evaluating fracture toughness as they are based on the mechanics of composite materials. The comparison of R-curves of hybrid configurations reveal that the insertion of carbon with glass at the interface of symmetric hybrid configuration enhances initial fracture toughness and stabilises whereas, with the change in layer configuration of anyone arm of the double-cantilever beam, the crack growth trend is also affected irrespective of same interface layers. The fractography analysis of delamination surfaces reveals that crack propagation through a resin-rich layer creates a rougher fracture surface resulting in higher energy dissipation as compared to crack propagation through resin-rich pockets. © 2021 Elsevier LtdItem Characterisation of fatigue delamination growth in plain woven hybrid laminated composites subjected to Mode-I loading(Elsevier B.V., 2024) Suman, M.L.J.; Murigendrappa, S.M.; Kattimani, S.Effect of similar and dissimilar crack plane interface configuration on fatigue delamination growth in plain woven hybrid composite laminates under Mode-I has been investigated. Constant displacement amplitude fatigue testing with displacement ratio of 0.1 was carried out on 3 configurations of plain woven glass/carbon epoxy composite laminates. A power law like fit between recorded delamination length and corresponding cycle was used to predict crack length for each of the cycle. Delamination growth rate,da/dN is computed by differentiating the expression of power-law like fit. The obtained crack growth rate for each of the specimens were plotted with respect to two normalised functions, G^Imax=GImax(a)/GIR(a) where GImax is maximum mode-I energy release rate and GIR(a) is the interlaminar fracture toughness resistance and ΔG^Ieff=G^Imax-G^Imin2 as crack driving parameters computed on the basis of Modified Beam Theory (MBT) and Valvo's mode partition method (MPV) are used in Paris relation to quantify delamination propagation. It is observed that the exponent values predicted by MBT method for G^Imax is lower as compared to ΔG^Ieff. Whereas, exponent values predicted for G^Imax is higher as compared to ΔG^Ieff predicted by MPV method. The higher the exponent value, the higher is the sensitivity of the model leading to uncertainties in the crack growth prediction. Also, it is to be noted that cyclic loading effect is when both GImax and GImin is considered, the use of ΔG^Ieff as crack driving parameter to quantify delamination propagation is justified. Secondly, MBT method does not account for the mode-mixity arising due to hybrid material configuration as in the case of Local Symmetry Fatigue (LSF) and Asymmetry Fatigue (ASF) specimens. Hence, results in higher exponent as compared to MPV method. On the other side, the G^Imax and ΔG^Ieff computed on the basis of MPV method is the pure Mode-I component deduced from the total energy release rate of mode-mixity. The equations of curve fitting is very much the same for Simple Symmetry Fatigue (SSF) specimens indicating that MBT and MPV methods predict pure Mode-I behaviour for symmetric configuration for delamination growth under fatigue Mode-I loading. From the composite laminate configuration point of view, LSF specimens have higher exponents as compared to ASF and SSF specimens indicating, local symmetry configuration laminates are highly sensitive to the small uncertainties and results in unstable crack growth. Comparison of results of all hybrid composite laminates shows that the normalised functions of G^Imax and ΔG^Ieff as crack driving parameters computed on the basis of MPV method is able to capture the effect of interlayers and stacking effect on the delamination growth in hybrid plain woven composites in fatigue loading and MPV method is found to be not sensitive to G^Imax and ΔG^Ieff for displacement ratio of 0.1. © 2023 Elsevier LtdItem Analysis of UNS S31603 ferrous joint made by rotary friction welding(Springer, 2024) Senthil Murugan, S.; Girisankar, S.; Devanathan, C.; Kattimani, S.This study delves into the effects of employing low friction pressure and high axial penetration during the fabrication of friction-welded joints using UNS S31603 stainless steel. The experiments were conducted using a continuous-drive rotary friction welding machine. Crucially, the research showcases the feasibility of creating robust welds in the metal, surpassing the strength of the parent metal. The resulting weld interfaces were remarkably narrow and well-defined. The mechanical properties of the welded joints, including tensile strength, yield strength, microhardness, impact toughness, and bending/flexural strength, were meticulously evaluated following ASTM standards. The findings indicate that the welded joints exhibited impressive tensile strength, approximately 803 MPa, and withstood a peak load of 52.0 kN. Additionally, these joints demonstrated a maximum elongation of 15.3% and a yield strength of 714.0 MPa. When subjected to bending conditions, similar joints made of UNS S31603 withstood loads of up to 19.0 kN before experiencing crack propagation. Ductility was observed in the fracture mode within the weld region, characterized by the formation of cup and cone necking, highlighting the joints' ductile behaviour. Furthermore, the joint efficiency was calculated to be over 100%. Utilizing these specific parameters, this method resulted in a maximum axial shortening or material loss of approximately 14 mm. © Indian Academy of Sciences 2024.Item Simulation of delamination propagation in laminated composites under Mode-I and Mixed-Mode bending with LCZ-Based R-curve cohesive zone modeling(Elsevier B.V., 2025) Chethan, H.C.; Kattimani, S.; Murigendrappa, S.M.For accurate prediction of the delamination behavior in the case of composite structures, toughening mechanisms like fiber bridging occurring in the fracture process zone (FPZ) must be considered. In this study, the relationship between the fiber bridging (R-curve) and the corresponding FPZ was investigated. Structural size, stacking sequence, and loading were considered in the study of the fiber-bridging behavior of composites. We propose an R-curve expression to estimate the variation of fracture toughness along the FPZ for structures of any configuration under mode-I and mixed-mode loading. These expressions are incorporated into simple bilinear softening laws to model the delamination behavior of any structural configuration under different loading conditions. The proposed methodology is computationally efficient, requiring simple measurements from experiments, such as initial and steady-state fracture toughness values. This eliminates the challenges of the conventional cohesive zone model in modeling large-scale bridging behavior in laminated composite structures. The proposed method was validated for different specimen configurations with variable thickness and cross-ply under mode-I loading. The effect of loading was investigated by subjecting a mixed-mode bending specimen to different mode ratios. The results indicated that the predicted values are in reasonable agreement with the measured values. © 2025 Elsevier Ltd