The Experts below are selected from a list of 387 Experts worldwide ranked by ideXlab platform
Paul R. Stoddart - One of the best experts on this subject based on the ideXlab platform.
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A low-cost and temperature-insensitive fibre Bragg grating sensor for monitoring localized strain concentrations
Measurement Science and Technology, 2009Co-Authors: C.e. Davis, H. C H Li, A. F. Dethlefsen, A Thompson, Paul R. StoddartAbstract:A simple, self-diagnostic strain sensor is described, based on a strongly reflective optical fibre Bragg grating illuminated by a broadband source. The total reflected power from these gratings is shown to be a function of the strain gradient experienced by the grating. This is because a change in pitch within a section of the grating results in the emergence of reflected energy in other spectral regions, without any significant reduction in the peak intensity at the Bragg wavelength. Thus, the presence of a localized strain can be inferred directly from an intensity measurement without the need for an optical filter or other more complex interrogation schemes. For spectrally flat light sources, the measurement is relatively insensitive to environmental temperature changes. The sensing mechanism can also be considered ‘self-diagnostic’ as a signal is returned by the grating even under zero load unless the sensor has failed. Modelling results are presented to determine the minimum grating strength required to achieve this effect, while the technique has been experimentally verified by measuring the strain transfer on a loaded Scarf Repair joint at room and elevated temperatures. The Scarf Repair was loaded to failure and a reduction in strain transfer was observed as the failure grew along the bondline, in accordance with finite element modelling results.
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composite Scarf Repair monitoring using fiber bragg grating sensors
The 14th International Symposium on: Smart Structures and Materials & Nondestructive Evaluation and Health Monitoring, 2007Co-Authors: I Herszberg, Claire Davis, Paul R. StoddartAbstract:Structural health monitoring (SHM) technology may be applied to composite bonded Repairs to enable the continuous through-life assessment of the Repair efficacy. This paper describes an SHM technique for the detection of debonding in composite Scarf Repairs using fibre optic Bragg grating strain sensors. A typical composite sandwich structure with a Scarf Repair on one surface is examined in this paper. A finite element study was conducted which showed that the strain in the debonded region changed significantly compared to the undamaged state. A differential strain approach was used to facilitate the detection of debonds, where two sensors were strategically positioned so that their strain differential increased as the damage propagated. With the use of matching gratings, this technique greatly reduced the support equipment requirement by converting the spectral information into an intensity-modulated signal, thus allowing a compact photodetector to be used for sensor interrogation. An experimental investigation was conducted to validate the theoretically predicted results. The experimental measurements agreed well with the numerical findings qualitatively, indicating that the proposed scheme has great potential as a simple and effective monitoring technique for composite Scarf Repairs.
Endel Iarve - One of the best experts on this subject based on the ideXlab platform.
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OPTIMAL DESIGN OF A COMPOSITE Scarf Repair PATCH UNDER TENSILE LOADING
2020Co-Authors: Timothy Breitzman, Endel Iarve, E R RipbergerAbstract:ABSTRACT Mechanics of the composite Scarf Repair under tensile loading with and without overlay plies was examined for nontraditional patch ply orientations. Three-dimensional nonlinear analysis was performed for Repair failure prediction and good baseline comparison for open-hole Scarfed panels and panels Repaired by using standard ply-by-ply replacement patch composition was achieved. Multidimensional optimization was performed to calculate the Repair patch ply orientations which minimize the von Mises stresses in the adhesive. These optimal stacking sequences achieved significant reduction of the stress levels and resulted in predicted up to 75% and 85% strength restoration for flush and single ply thickness over-ply Repair. These results are intended to illustrate additional design variables available for efficient composite Repair design, namely the composition of the Repair patch
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tensile failure of composite Scarf Repair
Structural Integrity and Durability of Advanced Composites#R##N#Innovative Modelling Methods and Intelligent Design, 2015Co-Authors: Endel Iarve, Timothy Breitzman, E R RipbergerAbstract:Composite Repair is an integral and critical aspect in the service and maintenance of growing fleets in the civil aerospace, automotive, and marine composite–vehicle industries. Bonded Repair and Scarf Repair are particularly attractive from strength restoration and technological standpoints, allowing one-sided access while only minimally affecting the outer shape of the structure. Mechanics of composite Scarf Repair under tensile loading, with and without overplies, were examined for the ply orientations of nontraditional patches. Three-dimensional nonlinear analysis was performed for composite Repair failure prediction. A baseline was achieved by comparing open-hole Scarfed panels with panels Repaired using standard ply-by-ply replacement patch composition. Multidimensional optimization was performed to calculate the Repair patch ply orientations that minimize von Mises stress in the adhesive. These optimal stacking sequences achieved significant reduction of stress levels and resulted in predictions of up to 60% and 90% strength restoration for flush and single-ply thickness overply Repairs, respectively. These results, supported by experimental data, are intended to illustrate additional design variables available for efficient composite Repair design, chiefly the composition of the Repair patch.
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optimization of a composite Scarf Repair patch under tensile loading
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Timothy Breitzman, Endel Iarve, B M Cook, Gregory A Schoeppner, Robert LiptonAbstract:Abstract Mechanics of the composite Repair under tensile loading with and without overlay plies was examined for nontraditional patch ply orientations. Three-dimensional nonlinear analysis was performed for Repair failure prediction and good baseline comparison for open hole Scarfed panels and panels Repaired by using standard ply-by-ply replacement patch composition was achieved. Multidimensional optimization was performed to calculate the Repair patch ply orientations which minimize the von Mises stresses in the adhesive. These optimal stacking sequences achieved significant reduction of the stress levels and resulted in predicted up to 85% and 90% strength restoration for flush and single ply thickness over-ply Repair. These results are intended to illustrate additional design variables available for efficient composite Repair design, namely the composition of the Repair patch.
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optimal design of a composite Scarf Repair patch under tensile loading
ASME 2010 International Mechanical Engineering Congress and Exposition, 2009Co-Authors: Timothy Breitzman, Endel Iarve, E R RipbergerAbstract:Mechanics of the composite Scarf Repair under tensile loading with and without overlay plies was examined for nontraditional patch ply orientations. Three-dimensional nonlinear analysis was performed for Repair failure prediction and good baseline comparison for open-hole Scarfed panels and panels Repaired by using standard ply-by-ply replacement patch composition was achieved. Multidimensional optimization was performed to calculate the Repair patch ply orientations which minimize the von Mises stresses in the adhesive. These optimal stacking sequences achieved significant reduction of the stress levels and resulted in predicted up to 75% and 85% strength restoration for flush and single ply thickness over-ply Repair. These results are intended to illustrate additional design variables available for efficient composite Repair design, namely the composition of the Repair patch.Copyright © 2009 by ASME
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optimal design of a composite Scarf Repair under uni axial tension loading
ASME 2008 International Mechanical Engineering Congress and Exposition, 2008Co-Authors: Timothy Breitzman, B M Cook, Gregory A Schoeppner, Endel IarveAbstract:Benchmark un-notched strength testing was used to characterize material properties for IM6/3501-6 composite material and to establish parameters for critical failure volume (CFV) (see [8]) analysis tools. Critical failure volume was used to predict the strength of Scarfed composites, as well as composites having a Scarf Repair patch. Baseline Repairs were created both without and with over-plies. Simplex optimization was performed on the analytical models to determine the Repair stacking sequence that would result in the largest tensile strength for the Repairs. The Repair was optimized in the linear elastic regime, but strength predictions took into account both geometric nonlinearities of the respective materials and the material nonlinearities of the adhesive. Predicted strengths were in good agreement with experimental results, and the resultant optimal designs increased the strength of the Repair under uni-axial tensile load by 10–20%.
Phillip J Crothers - One of the best experts on this subject based on the ideXlab platform.
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optimisation study of tapered Scarf and stepped lap joints in composite Repair patches
Composite Structures, 2015Co-Authors: Hamza Bendemra, Paul Compston, Phillip J CrothersAbstract:Abstract Stepped-lap Repairs of composite structures can offer an alternative that is easier to perform and less time-consuming to produce than the widely used tapered Scarf Repair. However, the design of stepped-lap joints must be carefully investigated in order to avoid generating stress concentration regions. This study investigates the influence of joint parameters on peak stresses in the adhesive bondline in tapered Scarf and stepped-lap joints. Linear finite element analysis was performed to conduct a parametric study with focus on six joint design parameters: ply thickness, adhesive thickness, taper angle, stacking sequence, overply layup, and overply lap length. Results showed that tapered Scarf and stepped-lap joints have a strong sensitivity to ply thickness, taper angle, and stacking sequence. The introduction of overplies provided protection and stiffness at joint tips, and a critical overply lap length was identified. The location of 0° plies in the composite laminates was highlighted as an important factor. The analysis was then extended to three-dimensional FE models for verification. In conclusion, results showed that high stress concentration in stepped-lap joints can be mitigated with the introduction of overplies and appropriate changes in joint design parameters to reduce stress peaks at joint tips and step corners.
Timothy Breitzman - One of the best experts on this subject based on the ideXlab platform.
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OPTIMAL DESIGN OF A COMPOSITE Scarf Repair PATCH UNDER TENSILE LOADING
2020Co-Authors: Timothy Breitzman, Endel Iarve, E R RipbergerAbstract:ABSTRACT Mechanics of the composite Scarf Repair under tensile loading with and without overlay plies was examined for nontraditional patch ply orientations. Three-dimensional nonlinear analysis was performed for Repair failure prediction and good baseline comparison for open-hole Scarfed panels and panels Repaired by using standard ply-by-ply replacement patch composition was achieved. Multidimensional optimization was performed to calculate the Repair patch ply orientations which minimize the von Mises stresses in the adhesive. These optimal stacking sequences achieved significant reduction of the stress levels and resulted in predicted up to 75% and 85% strength restoration for flush and single ply thickness over-ply Repair. These results are intended to illustrate additional design variables available for efficient composite Repair design, namely the composition of the Repair patch
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tensile failure of composite Scarf Repair
Structural Integrity and Durability of Advanced Composites#R##N#Innovative Modelling Methods and Intelligent Design, 2015Co-Authors: Endel Iarve, Timothy Breitzman, E R RipbergerAbstract:Composite Repair is an integral and critical aspect in the service and maintenance of growing fleets in the civil aerospace, automotive, and marine composite–vehicle industries. Bonded Repair and Scarf Repair are particularly attractive from strength restoration and technological standpoints, allowing one-sided access while only minimally affecting the outer shape of the structure. Mechanics of composite Scarf Repair under tensile loading, with and without overplies, were examined for the ply orientations of nontraditional patches. Three-dimensional nonlinear analysis was performed for composite Repair failure prediction. A baseline was achieved by comparing open-hole Scarfed panels with panels Repaired using standard ply-by-ply replacement patch composition. Multidimensional optimization was performed to calculate the Repair patch ply orientations that minimize von Mises stress in the adhesive. These optimal stacking sequences achieved significant reduction of stress levels and resulted in predictions of up to 60% and 90% strength restoration for flush and single-ply thickness overply Repairs, respectively. These results, supported by experimental data, are intended to illustrate additional design variables available for efficient composite Repair design, chiefly the composition of the Repair patch.
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optimization of a composite Scarf Repair patch under tensile loading
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Timothy Breitzman, Endel Iarve, B M Cook, Gregory A Schoeppner, Robert LiptonAbstract:Abstract Mechanics of the composite Repair under tensile loading with and without overlay plies was examined for nontraditional patch ply orientations. Three-dimensional nonlinear analysis was performed for Repair failure prediction and good baseline comparison for open hole Scarfed panels and panels Repaired by using standard ply-by-ply replacement patch composition was achieved. Multidimensional optimization was performed to calculate the Repair patch ply orientations which minimize the von Mises stresses in the adhesive. These optimal stacking sequences achieved significant reduction of the stress levels and resulted in predicted up to 85% and 90% strength restoration for flush and single ply thickness over-ply Repair. These results are intended to illustrate additional design variables available for efficient composite Repair design, namely the composition of the Repair patch.
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optimal design of a composite Scarf Repair patch under tensile loading
ASME 2010 International Mechanical Engineering Congress and Exposition, 2009Co-Authors: Timothy Breitzman, Endel Iarve, E R RipbergerAbstract:Mechanics of the composite Scarf Repair under tensile loading with and without overlay plies was examined for nontraditional patch ply orientations. Three-dimensional nonlinear analysis was performed for Repair failure prediction and good baseline comparison for open-hole Scarfed panels and panels Repaired by using standard ply-by-ply replacement patch composition was achieved. Multidimensional optimization was performed to calculate the Repair patch ply orientations which minimize the von Mises stresses in the adhesive. These optimal stacking sequences achieved significant reduction of the stress levels and resulted in predicted up to 75% and 85% strength restoration for flush and single ply thickness over-ply Repair. These results are intended to illustrate additional design variables available for efficient composite Repair design, namely the composition of the Repair patch.Copyright © 2009 by ASME
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optimal design of a composite Scarf Repair under uni axial tension loading
ASME 2008 International Mechanical Engineering Congress and Exposition, 2008Co-Authors: Timothy Breitzman, B M Cook, Gregory A Schoeppner, Endel IarveAbstract:Benchmark un-notched strength testing was used to characterize material properties for IM6/3501-6 composite material and to establish parameters for critical failure volume (CFV) (see [8]) analysis tools. Critical failure volume was used to predict the strength of Scarfed composites, as well as composites having a Scarf Repair patch. Baseline Repairs were created both without and with over-plies. Simplex optimization was performed on the analytical models to determine the Repair stacking sequence that would result in the largest tensile strength for the Repairs. The Repair was optimized in the linear elastic regime, but strength predictions took into account both geometric nonlinearities of the respective materials and the material nonlinearities of the adhesive. Predicted strengths were in good agreement with experimental results, and the resultant optimal designs increased the strength of the Repair under uni-axial tensile load by 10–20%.
Bin Liu - One of the best experts on this subject based on the ideXlab platform.
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study on impact damage mechanisms and tai capacity for the composite Scarf Repair of the primary load bearing level
Composite Structures, 2017Co-Authors: Bin Liu, Jian QinAbstract:Abstract As composite material plays a leading role in aircraft, composite bonding Repair has been extensively applied. Among composite bonding Repairs, the Scarf bonding Repair is widely adopted and has high Repair efficiency especially in primary load-bearing structures. However, the impact damage tolerance and impact damage mechanisms were not considered for Repaired structure integrity design yet. This paper experimentally and numerically studied the Scarfed bonding Repair of the advanced CFRP, which may suffer a low velocity impact load in service. At the central location of adhesive zone, impact energy and response regularity were studied to reveal the competition failure mechanism for inner kinds of materials. In the impact procedure, double force peaks phenomenon and four typical phases were found. Tension after impact (TAI) capacities were also tested to explain the impact damage effects on residual strength. The adhesive damage has strong influence over tension after impact capability. The most easily broken location in the bonded zone is the feathered tip on the back of impact point. The critical impact energy 23 J exists for this size of specimen. When the impact energy is higher than the critical 23 J, except for the composites damage, the adhesive damage can be observed at the second force dropping. The Scarfed adhesive damage occurred at the Scarf feathered tip of back side.
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experiment and design methods of composite Scarf Repair for primary load bearing structures
Composites Part A-applied Science and Manufacturing, 2016Co-Authors: Bin Liu, Rui Yan, Wei Feng, Wei XieAbstract:Abstract A relative thick plate of composite being Repaired by Scarf bonding was substituted as the Scarf joints and studied under tensile load in this paper. The experimental investigation told us the ultimate capability of load and failure mechanism of composite Scarf joints. In order to explain failure mechanism for Scarf bonding Repair of composite structures distinctly, FEM based on continuum damage mechanics (CDM) was carried out. CDM equations were derived by adding the delamination mode and 3D Hashin criteria based on strain into the composite constitutive relation. Furthermore, a modified semi-analytical method (MAM) was developed to obtain shear stress distribution in theory. MAM can improve the accuracy of Harman and Wang method, solve the stress asymmetry, obtain secondary peak of shear stress, and increase the highest peak of stress. In the end, the discussions for the methodologies of MAM, CDM and linear FEM were executed to compare the errors of predicting ultimate load. The discussion revealed that MAM has sufficient accuracy as an analytical methodology which could be utilized to design composite Scarf Repairs in a short cycle simply.
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experiment and design methods of composite Scarf Repair for primary load bearing structures part a applied science and manufacturing
Composites, 2016Co-Authors: Bin Liu, Rui Yan, Wei Feng, Wei XieAbstract:A relative thick plate of composite being Repaired by Scarf bonding was substituted as the Scarf joints and studied under tensile load in this paper. The experimental investigation told us the ultimate capability of load and failure mechanism of composite Scarf joints. In order to explain failure mechanism for Scarf bonding Repair of composite structures distinctly, FEM based on continuum damage mechanics (CDM) was carried out. CDM equations were derived by adding the delamination mode and 3D Hashin criteria based on strain into the composite constitutive relation. Furthermore, a modified semi-analytical method (MAM) was developed to obtain shear stress distribution in theory. MAM can improve the accuracy of Harman and Wang method, solve the stress asymmetry, obtain secondary peak of shear stress, and increase the highest peak of stress. In the end, the discussions for the methodologies of MAM, CDM and linear FEM were executed to compare the errors of predicting ultimate load. The discussion revealed that MAM has sufficient accuracy as an analytical methodology which could be utilized to design composite Scarf Repairs in a short cycle simply.
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parameters sensitivity and optimization for composite Scarf Repair
Journal of Reinforced Plastics and Composites, 2014Co-Authors: Bin Liu, Rui YanAbstract:Scarf Repair is the preferred method to restore the load-carrying capacity of the damaged structure of fiber-reinforced composite material when stiffness, strength, and flushness are needed. However, shear stress concentration occurs along the Scarf bond line coinciding with the location of 0° plies. Previous studies did not consider the sensitivity of parameters systematically and involve the interaction effect. In this paper, sensitivities of Scarf angle, adhesive thickness, and stacking sequence are evaluated synthetically through main effect and interaction effect by using the method of design of experiment. The general strategy of decreasing Scarf angle needs to remove more materials from parent laminate. Thus, a new strategy of changing the stacking sequence of Repair is performed to reduce the adhesive stress concentration by means of the optimization based on genetic algorithm. In spite of this, optimization results may not have good reliability especially when manufacture, load, and other fluctua...
