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S. K. Panigrahi - One of the best experts on this subject based on the ideXlab platform.
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structural design of single lap joints with delaminated frp composite adherends
Composites Part B-engineering, 2013Co-Authors: S. K. PanigrahiAbstract:Abstract This paper deals with the structural design of single lap joints (SLJs) with delaminated adherends using fracture mechanics principles. The interlaminar stresses and Strain Energy Release Rate (SERR) are considered as Damage characterizing parameters used for designing the SLJ when Delamination Damages are pre-embedded in both the adherends at similar positions. Three dimensional geometrically non-linear finite element analyses (FEAs) of SLJ with delaminated adherends have been performed to determine the interlaminar and SERR values along the Delamination fronts by simulating the simultaneous interaction Delamination Damages when pre-embedded at similar positions in both the adherends. SERR values are evaluated using Modified Crack Closure Technique (MCCI) which is based on energy principle. The Delaminations are assumed to be of linear front, and have been considered to be embedded in both the laminated FRP composite adherends beneath the surface ply of the adhesively bonded SLJ. The Delamination Damages are presumed either to pre-exist or get evolved at the interlaminar locations. Such Delaminations have been modelled using the sublaminate technique. The critical issues of modelling pre-embedded Delamination Damages are discussed in detail. The numerical results presented in this paper are based on the validated FE model compared with the available literature. Based on the present analyses, the structural design recommendations have been made for the SLJ when pre-embedded Delamination Damages are present in both the adherends. It is observed from the stress based design that the Delamination Damage when present in the bottom adherend is more detrimental for failure of SLJ compared to that for the case when it is present in the top adherend. Also, SERR based design reveals that the opening mode predominantly governs the propagation of Delamination Damage for all positions of the pre-embedded Delaminations in both the adherends of the SLJ.
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Through-the-width Delamination Damage propagation characteristics in single-lap laminated FRP composite joints
International Journal of Adhesion and Adhesives, 2009Co-Authors: S. K. Panigrahi, B. PradhanAbstract:Three-dimensional non-linear finite element analyses have been carried out to study the effects of through-the-width Delaminations on Delamination Damage propagation characteristics in adhesively bonded single-lap laminated FRP composite joints. The Delaminations have been presumed either to pre-exist or to get evolved due to coupled stress failure criteria in the laminated FRP composite adherends near the overlap ends beneath the ply adjacent to the overlap region. The out-of-plane stresses in the adhesive layer, the interlaminar stress distributions along the Delamination fronts and the strain energy release rates (SERRs) corresponding to the three individual modes have been evaluated for varying positions of the Delaminations pre-embedded in either of the adherends. A good matching between the present 3D results and experimental and analytical solution of the literature has been established for the unDamaged and a Damaged model. A significant difference in the interlaminar stresses and the SERR values has been observed and is largely dependent on the adherends (bottom or top) possessing the through-the-width Delamination Damages. Also, the interlaminar stresses and SERR values along the two corresponding Delamination fronts are different. Accordingly, it can be concluded that the positions of the through-the-width Delaminations significantly influence the Delamination Damage propagation behaviour vis-a-vis the performance of the composite joint.
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Delamination Damage Analyses of FRP Composite Spar Wingskin Joints with Modified Elliptical Adhesive Load Coupler Profile
Applied Composite Materials, 2008Co-Authors: S. K. Panigrahi, B. PradhanAbstract:Three-dimensional non-linear finite element analyses (FEA) for Delamination Damage onset and its growth in Graphite Fiber Reinforced Plastic (GFRP) composite Spar Wingskin Joints (SWJ) with modified elliptical adhesive load coupler profile for varied ratios of base width to height of the spar have been presented in this paper. Both in-plane and out-of-plane normal and shear stress variations on the interfacial surface of the wingskin between the spar and the wingskin have been evaluated. Coupled stress failure criterion has been used to predict the locations of initiation of failures due to Delamination induced Damages. Based on the stress and Delamination Damage analyses, suitable geometry of the modified elliptical adhesive load coupler profile of the SWJ has been recommended. The Delamination Damage has been observed to be initiated from the toe-end of the interfacial surface of the spar and the wingskin of the SWJ. Subsequently, the Delamination propagations have also been studied by calculating the individual and the total Mode of Strain Energy Release Rate (SERR) along the Delamination front using Modified Crack Closure Integral (MCCI) technique based on Linear Elastic Fracture Mechanics (LEFM) approach. It is seen that SERR variations along the Delamination front i.e. across the width of the SWJ are not uniform. Therefore, a straight Delamination front may grow into a curved Delamination front as the Delamination propagates. Also, it is found that Mode I SERR ( G _I) governs the Delamination propagation predominantly for the SWJ. Accordingly, suitable Delamination arresting mechanism has been suggested.
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onset and growth of adhesion failure and Delamination induced Damages in double lap joint of laminated frp composites
Composite Structures, 2008Co-Authors: S. K. Panigrahi, B. PradhanAbstract:Abstract Three-dimensional non-linear finite element analyses have been carried out for graphite/epoxy laminated FRP composite double lap joints (DLJ) to study the onset and growth of adhesion failure and Delamination induced Damages. Out-of-plane stresses on different interfacial surfaces of the DLJ have been determined. The peel and shear stress distributions in the adhesive layer have been evaluated and compared with the existing analytical and numerical solutions showing good agreement. Tsai–Wu coupled stress failure criterion has been employed to identify the critical locations for the onset of adhesion failure and Delamination induced Damages. Modified crack closure integral (MCCI) technique based on the concept of linear elastic fracture mechanics (LEFM) has been followed to calculate the three individual modes of strain energy release rates (SERR) G I , G II and G III along the Damage fronts of pre-embedded Damages due to the adhesion failure and the Delamination induced Damage for studying the Damage propagation. The critical locations for the onset of the adhesion failure and the Delamination induced Damages have been found to be on the interfacial surfaces between the main adherend and the adhesive layer and on the surface between the first and second plies of the main adherend beneath the adhesive layer within the overlap region of the DLJ, respectively. The SERR in the shearing mode is the governing mode for the propagation of the adhesion failure and the SERR in the opening mode controls the propagation of the Delamination Damage. However, the contributions of G I and G III along the adhesion failure front cannot be outrightly ignored. Therefore, it can be said that the adhesion failure would propagate under mixed mode condition, while Delamination Damage propagation would be predominantly due to the mode I. Also, it has been observed that the adhesion failure is more detrimental than the Delamination Damages for the failure of DLJ when the DLJ is embedded with both types of Damages.
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Delamination Damage analyses of adhesively bonded lap shear joints in laminated FRP composites
International Journal of Fracture, 2007Co-Authors: S. K. Panigrahi, B. PradhanAbstract:Three-dimensional non-linear finite ele- ment analyses have been carried out to evaluate the out-of-plane stresses in the adhesive layer existing between the lap and the strap adherends of the Lap Shear Joint (LSJ) in laminated FRP composites for varied Delamination lengths. The Delaminations are presumed to be pre-embedded in the thin resin rich layer existing between the first and second plies of the strap adherend. Sublaminate technique has been used to model the LSJ with the Delamination. Contact finite element analyses have been performed in order to avoid interpenetration of delaminated surfaces. The effects of varied Delamination lengths on the peel and interlaminar shear stresses and the individual modes of Energy Release Rate (ERR) in the Delamination zones are highlighted in this paper. It is seen that three-dimensional effects exist near the free edges of the overlap end of the joint. The Delamination propagation significantly affects the stress distributions in the adhesive layer existing between the lap and the strap adherends of the LSJ. The variations of interlaminar stresses and ERRs on both the Delamination fronts are found to be significantly different and thus, indicate that the propagation of Delamination does not occur at same rate at the two Delamination fronts. This may throw some light to the evaluation of structural integrity of the LSJ in the presence of pre-embedded Delaminations.
B. Pradhan - One of the best experts on this subject based on the ideXlab platform.
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Delamination Damage analysis of laminated bonded tubular single lap joint made of fiber reinforced polymer composite
International Journal of Damage Mechanics, 2014Co-Authors: Rashmi Ranjan Das, B. PradhanAbstract:Onset and growth of Delamination Damages in laminated fiber-reinforced polymer composite made bonded tubular single lap joints have been thoroughly studied through a finite element analysisbased simulation technique developed in the present research. The model provides sufficient scope for a comprehensive parametric study of the bonded structure in terms of three-dimensional stress analyses within the joint, studying the Delamination Damage onset and growth characteristics, and investigating its effect on stress distributions in the joint and both the adherends (outer and inner). Quadratic failure criterion has been used to depict Delamination Damage-induced cohesion failure within the adhesive layer. Whereas Tsai–Wu coupled stress criterion has been used for locating the Delamination and adhesion failure prone regions at ply-interfaces of the adherends and adherend–adhesive interfaces within the joint, respectively. Three-dimensional stress analyses revealed that outer adherend of the bonded tubular single lap joints experiences comparatively higher interlaminar peel (� r) and shear stress (� rz, � r� ) concentrations at the free edge of the first ply-interface and is likely to delaminate at this edge. Accordingly, preembedded through-the-circumference Delamination Damages have been simulated at this edge, and contact finite element analyses have been performed in order to avoid interpenetration of delaminated surfaces. Strain energy release rate calculated using modified crack closure integral vis-a`-vis virtual crack closure technique has been used as the characterizing parameter for assessing the growth of the Damages. Free edge Delamination in the outer adherend has been observed to propagate in a self-similar manner mainly in the in-plane shearing mode. It causes peel and shear stress concentrations in regions of the adherend–adhesive interfaces and first ply-interface of the inner adherend, localized to the clamped
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Through-the-width Delamination Damage propagation characteristics in single-lap laminated FRP composite joints
International Journal of Adhesion and Adhesives, 2009Co-Authors: S. K. Panigrahi, B. PradhanAbstract:Three-dimensional non-linear finite element analyses have been carried out to study the effects of through-the-width Delaminations on Delamination Damage propagation characteristics in adhesively bonded single-lap laminated FRP composite joints. The Delaminations have been presumed either to pre-exist or to get evolved due to coupled stress failure criteria in the laminated FRP composite adherends near the overlap ends beneath the ply adjacent to the overlap region. The out-of-plane stresses in the adhesive layer, the interlaminar stress distributions along the Delamination fronts and the strain energy release rates (SERRs) corresponding to the three individual modes have been evaluated for varying positions of the Delaminations pre-embedded in either of the adherends. A good matching between the present 3D results and experimental and analytical solution of the literature has been established for the unDamaged and a Damaged model. A significant difference in the interlaminar stresses and the SERR values has been observed and is largely dependent on the adherends (bottom or top) possessing the through-the-width Delamination Damages. Also, the interlaminar stresses and SERR values along the two corresponding Delamination fronts are different. Accordingly, it can be concluded that the positions of the through-the-width Delaminations significantly influence the Delamination Damage propagation behaviour vis-a-vis the performance of the composite joint.
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Delamination Damage Analyses of FRP Composite Spar Wingskin Joints with Modified Elliptical Adhesive Load Coupler Profile
Applied Composite Materials, 2008Co-Authors: S. K. Panigrahi, B. PradhanAbstract:Three-dimensional non-linear finite element analyses (FEA) for Delamination Damage onset and its growth in Graphite Fiber Reinforced Plastic (GFRP) composite Spar Wingskin Joints (SWJ) with modified elliptical adhesive load coupler profile for varied ratios of base width to height of the spar have been presented in this paper. Both in-plane and out-of-plane normal and shear stress variations on the interfacial surface of the wingskin between the spar and the wingskin have been evaluated. Coupled stress failure criterion has been used to predict the locations of initiation of failures due to Delamination induced Damages. Based on the stress and Delamination Damage analyses, suitable geometry of the modified elliptical adhesive load coupler profile of the SWJ has been recommended. The Delamination Damage has been observed to be initiated from the toe-end of the interfacial surface of the spar and the wingskin of the SWJ. Subsequently, the Delamination propagations have also been studied by calculating the individual and the total Mode of Strain Energy Release Rate (SERR) along the Delamination front using Modified Crack Closure Integral (MCCI) technique based on Linear Elastic Fracture Mechanics (LEFM) approach. It is seen that SERR variations along the Delamination front i.e. across the width of the SWJ are not uniform. Therefore, a straight Delamination front may grow into a curved Delamination front as the Delamination propagates. Also, it is found that Mode I SERR ( G _I) governs the Delamination propagation predominantly for the SWJ. Accordingly, suitable Delamination arresting mechanism has been suggested.
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onset and growth of adhesion failure and Delamination induced Damages in double lap joint of laminated frp composites
Composite Structures, 2008Co-Authors: S. K. Panigrahi, B. PradhanAbstract:Abstract Three-dimensional non-linear finite element analyses have been carried out for graphite/epoxy laminated FRP composite double lap joints (DLJ) to study the onset and growth of adhesion failure and Delamination induced Damages. Out-of-plane stresses on different interfacial surfaces of the DLJ have been determined. The peel and shear stress distributions in the adhesive layer have been evaluated and compared with the existing analytical and numerical solutions showing good agreement. Tsai–Wu coupled stress failure criterion has been employed to identify the critical locations for the onset of adhesion failure and Delamination induced Damages. Modified crack closure integral (MCCI) technique based on the concept of linear elastic fracture mechanics (LEFM) has been followed to calculate the three individual modes of strain energy release rates (SERR) G I , G II and G III along the Damage fronts of pre-embedded Damages due to the adhesion failure and the Delamination induced Damage for studying the Damage propagation. The critical locations for the onset of the adhesion failure and the Delamination induced Damages have been found to be on the interfacial surfaces between the main adherend and the adhesive layer and on the surface between the first and second plies of the main adherend beneath the adhesive layer within the overlap region of the DLJ, respectively. The SERR in the shearing mode is the governing mode for the propagation of the adhesion failure and the SERR in the opening mode controls the propagation of the Delamination Damage. However, the contributions of G I and G III along the adhesion failure front cannot be outrightly ignored. Therefore, it can be said that the adhesion failure would propagate under mixed mode condition, while Delamination Damage propagation would be predominantly due to the mode I. Also, it has been observed that the adhesion failure is more detrimental than the Delamination Damages for the failure of DLJ when the DLJ is embedded with both types of Damages.
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Delamination Damage analyses of adhesively bonded lap shear joints in laminated FRP composites
International Journal of Fracture, 2007Co-Authors: S. K. Panigrahi, B. PradhanAbstract:Three-dimensional non-linear finite ele- ment analyses have been carried out to evaluate the out-of-plane stresses in the adhesive layer existing between the lap and the strap adherends of the Lap Shear Joint (LSJ) in laminated FRP composites for varied Delamination lengths. The Delaminations are presumed to be pre-embedded in the thin resin rich layer existing between the first and second plies of the strap adherend. Sublaminate technique has been used to model the LSJ with the Delamination. Contact finite element analyses have been performed in order to avoid interpenetration of delaminated surfaces. The effects of varied Delamination lengths on the peel and interlaminar shear stresses and the individual modes of Energy Release Rate (ERR) in the Delamination zones are highlighted in this paper. It is seen that three-dimensional effects exist near the free edges of the overlap end of the joint. The Delamination propagation significantly affects the stress distributions in the adhesive layer existing between the lap and the strap adherends of the LSJ. The variations of interlaminar stresses and ERRs on both the Delamination fronts are found to be significantly different and thus, indicate that the propagation of Delamination does not occur at same rate at the two Delamination fronts. This may throw some light to the evaluation of structural integrity of the LSJ in the presence of pre-embedded Delaminations.
Mohd Shukry Abdul Majid - One of the best experts on this subject based on the ideXlab platform.
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critical thrust force and critical feed rate in drilling flax fibre composites a comparative study of various thrust force models
Composites Part B-engineering, 2019Co-Authors: Aiman Akmal Abdul Nasir, Ai Azmi, Mohd Shukry Abdul MajidAbstract:Abstract Past experimental and analytical studies for determination of critical thrust force that contributed toward minimal Delamination Damage in drilling synthetic fibre reinforced composites have failed to consider the recently developed natural fibre composites. From this point of view, critical thrust force and feed rate in drilling of flax fibre composites were comprehensively investigated. Three different thrust force models that were based on linear elastic fracture mechanics and properties of the composites; namely, Mode I interlaminar fracture toughness, Young modulus and Poisson ratio, were applied in order to determine the critical thrust force values. Empirical relationships between various feed rates and spindle rotational speeds with the drilling thrust force were established via regression analyses. These relationships would aid in predicting the critical feed rate while drilling the aforementioned composites. The results reveal that critical feed rate in between the range of 0.15–0.18 mm/rev was desirable for minimisation of the onset Delamination Damage on the composite laminates. However, the stiffer crystalline structure of the flax fibres as compared to the synthetic fibres inflicted toward the presence of Delamination Damage below the critical feed rate and thrust force values.
Aiman Akmal Abdul Nasir - One of the best experts on this subject based on the ideXlab platform.
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critical thrust force and critical feed rate in drilling flax fibre composites a comparative study of various thrust force models
Composites Part B-engineering, 2019Co-Authors: Aiman Akmal Abdul Nasir, Ai Azmi, Mohd Shukry Abdul MajidAbstract:Abstract Past experimental and analytical studies for determination of critical thrust force that contributed toward minimal Delamination Damage in drilling synthetic fibre reinforced composites have failed to consider the recently developed natural fibre composites. From this point of view, critical thrust force and feed rate in drilling of flax fibre composites were comprehensively investigated. Three different thrust force models that were based on linear elastic fracture mechanics and properties of the composites; namely, Mode I interlaminar fracture toughness, Young modulus and Poisson ratio, were applied in order to determine the critical thrust force values. Empirical relationships between various feed rates and spindle rotational speeds with the drilling thrust force were established via regression analyses. These relationships would aid in predicting the critical feed rate while drilling the aforementioned composites. The results reveal that critical feed rate in between the range of 0.15–0.18 mm/rev was desirable for minimisation of the onset Delamination Damage on the composite laminates. However, the stiffer crystalline structure of the flax fibres as compared to the synthetic fibres inflicted toward the presence of Delamination Damage below the critical feed rate and thrust force values.
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experimental study towards determination of critical feed for minimization of Delamination Damage in drilling flax natural fibre composites
Procedia CIRP, 2018Co-Authors: Aiman Akmal Abdul Nasir, Azwan Iskandar Azmi, Tan Chye Lih, Norshah Aizat ShuaibAbstract:Abstract Mechanical joint is the weakest link of any fibre reinforced polymer composite structures. The holes for the joints are often created through conventional mechanical drilling due to the technological know-how. Yet, Delamination Damage at the entry and the exit side of the drilled holes are critical defects that severely influence mechanical competence of the product. However, the main challenge in controlling and reducing thrust force during drilling operation is variation of mechanical properties of composite material, particularly for flax fibre based products. The influence and relationship of critical thrust force and feed rate on Delamination Damage in drilling flax natural fibre composites was investigated. Initially, the critical thrust force for minimal Delamination Damage was determined based on existing models for synthetic fibre reinforced polymer composites. A semi-empirical model that correlates feed rate with critical thrust force was established via regression analyses. This model allows prediction of critical feed rate at a constant cutting speed. The model could minimise the on-set Delamination Damage of the composite laminates. Experimental results confirmed that the Delamination factor was mainly governed by the choice of feed rate. The inter-laminar strength of the flax fibre composite was attributed to the initiation of Delamination Damage. The critical strain release energy is significantly different in comparison with carbon and glass fibre composites counterparts.
Jianwu Zhou - One of the best experts on this subject based on the ideXlab platform.
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effect of z pin inclined angle on the impact Damage suppression effectiveness for cross ply composite laminates
Composites Part A-applied Science and Manufacturing, 2021Co-Authors: Binbin Liao, Jianwu Zhou, Jinyang Zheng, Ran Tao, Tian Zhao, Daining FangAbstract:Abstract Z-pins can enhance through-thickness direction of composite laminates effectively by reducing the Delamination Damage area. In this paper, the low velocity impact behaviors of [02/902]4S cross-ply composite laminates by inserting Z-pins with two different angle 0° and ±45° along the thickness direction were compared. T300 carbon fiber Z-pins were used as the reinforcements for Z-pinned laminates impacted by 5 J, 10 J, 20 J and 30 J impact energies. The mechanical responses including the impact force-time/central displacement curves were recorded during the tests. Afterwards, ultrasonic C-scanner, scanning electron microscope (SEM) and X-ray micro-computed tomography (μCT) techniques were used to characterize the impact Damage. Experimental results demonstrated that the Z-pins were unable to delay the Delamination initiation, which led to basically consistent Delamination initiation threshold regardless of Z-pin inclined angle. Based on the mechanical characteristics, 0° Z-pinning could improve the resistance to the onset of penetration by comparing to the ±45° Z-pinning. In addition, the effectiveness of 0° Z-pinning on suppression of Delamination Damage and internal defects was better than the ±45° Z-pinning at high impact energy.
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low velocity impact behavior and residual tensile strength of cfrp laminates
Composites Part B-engineering, 2019Co-Authors: Jianwu Zhou, Binbin Liao, Yaoyao Shi, Yangjie Zuo, Hongliang Tuo, Liyong JiaAbstract:Abstract This paper experimentally studies the low-velocity impact behaviors and residual tensile strength of carbon fiber reinforced plastics (CFRP) laminates. Firstly, the effects of four factors, i.e. impact angle, impactor diameter, the proportion of ply orientation and stacking sequence, on the impact responses of laminates are studied. The Damage characteristics are evaluated by dent depth, Delamination Damage projection area (DDPA) and energy dissipation. Secondly, the tensile responses of the laminates after impact are investigated based on residual tensile strength (RTS). Finally, the correlations between the four Damage evaluation criteria, i.e. dent depth, DDPA, energy dissipation and RTS, are sorted out. Experimental results demonstrate that the four factors have significant effects on the impact behaviors of laminates in different ways. The DDPA is negatively correlated with the dent depth of laminates, and the dent depth can be treated as an important reference for the RTS. Besides, a fracture phenomenon, i.e. a clear band of fiber fracture around the impact area after impact, has been observed and discussed.