Effective bulk properties of fiber-reinforced composites can be determined from individual constituent properties through spatial homogenization. Homogenization, in this regard, is conducted over a specifically selected volume of the material that is sufficiently small to capture complex local deformation response, while large enough to encompass all individual components, i.e. fibers and matrix. The physical dimension of such homogenization volumes is a key parameter in multiscale studies. Experimental measurement of the length scale at which the transition from micro to macroscale response occurs is challenging. In the present study, we propose a systematic approach to estimate the physical dimensions of a micro-to-macro transition length scale in terms of the number of fibers in the transverse plane of a cross-ply laminate subjected to remote tensile load. In-house fabricated cross-ply composite samples are loaded in tension in a miniature tensile frame inside a scanning electron microscope, while images are acquired from a small area of interest located on the transverse ply. Digital Image Correlation (DIC) is utilized to obtain full-field strain distribution within the area of interest at various global stress/strain intervals. Spatial averaging of strains at mesoscale is used to determine the micro-to-macro transition scale.
{"title":"Meso-Scale Strain Measurements in Fiber Reinforced Composites","authors":"B. Koohbor, C. Montgomery, S. White, N. Sottos","doi":"10.12783/ASC33/26028","DOIUrl":"https://doi.org/10.12783/ASC33/26028","url":null,"abstract":"Effective bulk properties of fiber-reinforced composites can be determined from individual constituent properties through spatial homogenization. Homogenization, in this regard, is conducted over a specifically selected volume of the material that is sufficiently small to capture complex local deformation response, while large enough to encompass all individual components, i.e. fibers and matrix. The physical dimension of such homogenization volumes is a key parameter in multiscale studies. Experimental measurement of the length scale at which the transition from micro to macroscale response occurs is challenging. In the present study, we propose a systematic approach to estimate the physical dimensions of a micro-to-macro transition length scale in terms of the number of fibers in the transverse plane of a cross-ply laminate subjected to remote tensile load. In-house fabricated cross-ply composite samples are loaded in tension in a miniature tensile frame inside a scanning electron microscope, while images are acquired from a small area of interest located on the transverse ply. Digital Image Correlation (DIC) is utilized to obtain full-field strain distribution within the area of interest at various global stress/strain intervals. Spatial averaging of strains at mesoscale is used to determine the micro-to-macro transition scale.","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115274153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On The Use of Multifunctional Z-Pins for Sensing Internal Damage in Composite Laminates Based on Electrical Resistance Measurements","authors":"R. Hart","doi":"10.12783/asc33/26120","DOIUrl":"https://doi.org/10.12783/asc33/26120","url":null,"abstract":"","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116612376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Ko, K. Chan, Reed Hawkins, Rohith Jayaram, C. Lynch, Reda El Mamoune, M. Nguyen, Nicolay Pekhotin, N. Stokes, Daniel N. Wu, M. Tuttle, Jinkyu Yang, M. Salviato
In this paper, we investigate the intra-laminar size effect of discontinuous fiber composites (DFCs) with three different unidirectional prepreg platelet sizes (75×12, 50×8, and 25×4 mm). Experimentally, we test five different sizes of single edge notched specimens, geometrically scaled (1:2/3:1/3:1/6:1/20), with the constant thickness. We observe notch insensitivity meaning that the crack initiate away from the notch, when the structure sizes are small (from the ratio 1/20 to 1/6). However, the crack always initiate for the ratio of 2/3 and 1. Bazants size effect law is used to analyze such unconventional fracturing behaviors. The experimental results are fitted using the linear regression analysis follow by the size effect law. The transition behavior of the DFCs from the strength based criteria to the energy based criteria is clearly observed. Also, as the platelet size increases, the fracture behaviors shift away from the energy based criteria, which implies a decrease in brittleness. To obtain the intra-laminar fracture energy, Gf , we have developed a finite element model based on the stochastic laminate analogy. The platelet size of 75×12 mm shows 96.8% increase in the fracture energy compared to the platelet size of 25×4 mm while behaves less brittle way. In conclusion, this study examines the effect of the platelet sizes of the DFCs in the presence of the notch. In this process, capturing the quasi-brittleness of the material using the nonlinear fracture mechanics is essential and we accomplish this using the simple size effect law. This work expands on an earlier SAMPE conference proceeding [1], and thus, there is a significant overlap in texts and figures between this and the SAMPE conference proceedings.
{"title":"Experimental and Numerical Characterization of the Intra-Laminar Fracturing Behavior in Discontinuous Fiber Composite Structures","authors":"S. Ko, K. Chan, Reed Hawkins, Rohith Jayaram, C. Lynch, Reda El Mamoune, M. Nguyen, Nicolay Pekhotin, N. Stokes, Daniel N. Wu, M. Tuttle, Jinkyu Yang, M. Salviato","doi":"10.12783/ASC33/26079","DOIUrl":"https://doi.org/10.12783/ASC33/26079","url":null,"abstract":"In this paper, we investigate the intra-laminar size effect of discontinuous fiber composites (DFCs) with three different unidirectional prepreg platelet sizes (75×12, 50×8, and 25×4 mm). Experimentally, we test five different sizes of single edge notched specimens, geometrically scaled (1:2/3:1/3:1/6:1/20), with the constant thickness. We observe notch insensitivity meaning that the crack initiate away from the notch, when the structure sizes are small (from the ratio 1/20 to 1/6). However, the crack always initiate for the ratio of 2/3 and 1. Bazants size effect law is used to analyze such unconventional fracturing behaviors. The experimental results are fitted using the linear regression analysis follow by the size effect law. The transition behavior of the DFCs from the strength based criteria to the energy based criteria is clearly observed. Also, as the platelet size increases, the fracture behaviors shift away from the energy based criteria, which implies a decrease in brittleness. To obtain the intra-laminar fracture energy, Gf , we have developed a finite element model based on the stochastic laminate analogy. The platelet size of 75×12 mm shows 96.8% increase in the fracture energy compared to the platelet size of 25×4 mm while behaves less brittle way. In conclusion, this study examines the effect of the platelet sizes of the DFCs in the presence of the notch. In this process, capturing the quasi-brittleness of the material using the nonlinear fracture mechanics is essential and we accomplish this using the simple size effect law. This work expands on an earlier SAMPE conference proceeding [1], and thus, there is a significant overlap in texts and figures between this and the SAMPE conference proceedings.","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125059292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yosuke Nukui, Shunsuke Harashima, A. Takenaga, T. Mochizuki
The diameter of glass fiber chopped strands used for injection molding is usually from 10μm to 15μm. On the other hand, some reports have stated that the mechanical property is improved by slimming the diameter of the glass fiber chopped strands. By increasing the surface area between the glass fiber and matrix resin, in other words, an increase in the interface to bear the load is the main factor of this improvement. However, their report focused on the short-term load, so the effect on the durability strength has not been reported. This study was made to investigate the effect on the durability property by using low diameter fibers. In addition, we investigated the effect of using high strength and high modulus glass composition fibers on the durability property.
{"title":"Improvement of Durability Property by Using Low Diameter Glass Chopped Strands","authors":"Yosuke Nukui, Shunsuke Harashima, A. Takenaga, T. Mochizuki","doi":"10.12783/ASC33/25968","DOIUrl":"https://doi.org/10.12783/ASC33/25968","url":null,"abstract":"The diameter of glass fiber chopped strands used for injection molding is usually from 10μm to 15μm. On the other hand, some reports have stated that the mechanical property is improved by slimming the diameter of the glass fiber chopped strands. By increasing the surface area between the glass fiber and matrix resin, in other words, an increase in the interface to bear the load is the main factor of this improvement. However, their report focused on the short-term load, so the effect on the durability strength has not been reported. This study was made to investigate the effect on the durability property by using low diameter fibers. In addition, we investigated the effect of using high strength and high modulus glass composition fibers on the durability property.","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131552645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we describe the mechanics of edge cracking and methods for determining the fracture toughness of strain locking materials using homogenized constitutive models for strain locking materials. We implemented a thermodynamically consistent constitutive model for a strain locking material into a plane stress finite element model and determined the energy release rate for a single-edge cracked configuration. Using material parameters suitable for a copper-clad polymer flexible circuit board and for a biological material, we determined the relationship between the strain energy release rate and the crack length for an applied load history using crackadvance methodology. The change of total potential energy (П = - (U-W)) as an edge crack propagates through a prismatic bar loaded in tension is determined. A polynomial is fitted to П where U is the total strain energy stored and W is the work done by the external loads for the purpose of differentiating with respect to the crack length, a. The energy release rate, G, is derived from the slope Π as a function of crack length from these numerical results. Additionally, an additively manufactured strain locking composite material specimen is produced and tensile tested. The results are used to fit the material constants to a previously derived implicit nonlinear elastic model.
{"title":"Mechanics of Edge-Cracking and Toughness Determination for Strain Locking Composite Materials","authors":"N. Payne, K. Pochiraju","doi":"10.12783/ASC33/25950","DOIUrl":"https://doi.org/10.12783/ASC33/25950","url":null,"abstract":"In this paper, we describe the mechanics of edge cracking and methods for determining the fracture toughness of strain locking materials using homogenized constitutive models for strain locking materials. We implemented a thermodynamically consistent constitutive model for a strain locking material into a plane stress finite element model and determined the energy release rate for a single-edge cracked configuration. Using material parameters suitable for a copper-clad polymer flexible circuit board and for a biological material, we determined the relationship between the strain energy release rate and the crack length for an applied load history using crackadvance methodology. The change of total potential energy (П = - (U-W)) as an edge crack propagates through a prismatic bar loaded in tension is determined. A polynomial is fitted to П where U is the total strain energy stored and W is the work done by the external loads for the purpose of differentiating with respect to the crack length, a. The energy release rate, G, is derived from the slope Π as a function of crack length from these numerical results. Additionally, an additively manufactured strain locking composite material specimen is produced and tensile tested. The results are used to fit the material constants to a previously derived implicit nonlinear elastic model.","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132582924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Ryan, R. Wheeler, G. Kedziora, Andrew Sharits, Samit Roy, J. Moller, I. Sizemore, D. Nepal
{"title":"MoS2 Dispersed Epoxy Composite: Influence of Solvent Quality and Surface Chemistry to Local Chemical Network Formation and its Influence on Nanoscale Toughening Mechanism","authors":"J. Ryan, R. Wheeler, G. Kedziora, Andrew Sharits, Samit Roy, J. Moller, I. Sizemore, D. Nepal","doi":"10.12783/asc33/26142","DOIUrl":"https://doi.org/10.12783/asc33/26142","url":null,"abstract":"","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134416178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Pigazzini, D. Kamensky, D. Iersel, J. Remmers, Y. Bazilevs
High-fidelity progressive damage simulations of composite materials are important for advancements in damage tolerant design. We recently proposed a novel modeling approach for damage analysis of composite laminates, in which multi-layer structures are represented as individual plies connected through zero-Thickness cohesive interfaces. The model is developed in the framework of Isogeometric Analysis (IGA). By using Non-Uniform Rational B-Spline (NURBS) basis functions for representing geometries and discretizing the displacement field, IGA allows for a more direct connection between numerical simulation and CAD software. In addition, compared to traditional polynomial basis functions, NURBS functions allow for better representation of geometries and higher order inter-element continuity properties. The computational efficiency of the proposed modeling approach stems from the adoption of Kirchhoff-Love shell elements for the modeling of individual lamina. Intralaminar damage is introduced in the framework of continuum damage mechanics, in which a strain-softening damage model drives the degradation of material elastic properties. However, the use of local strain measures, in combination with strainsoftening degradation models, may lead to damage localization problems. These cause the governing equations to become ill-posed and their approximate solution to be highly mesh-sensitive. Our work aims to re-establish the objectivity with respect to the adopted discretization. We extend our analysis framework by introducing a smoothed strain field to re-place the local strain measures used in the damage model. Our approach builds on the Gradient-Enhanced Damage (GED) model and is specialized for the Kirchhoff-Love shell structural model. The smoothed strain field is obtained by solving an additional set of partial differential equations on each ply of the composite laminate. The GED model can be applied to smooth tensor-valued quantities, such as strains, on generic-shaped geometries in the three-dimensional space, including complex and curved aerospace structures modeled by means of shell elements. In this work, we propose numerical examples in order to illustrate the validity of the GED model.
{"title":"Non-Local Damage Modeling for Composite Laminates: Application to Isogeometric Analysis for Impact Simulations","authors":"M. Pigazzini, D. Kamensky, D. Iersel, J. Remmers, Y. Bazilevs","doi":"10.12783/asc33/26077","DOIUrl":"https://doi.org/10.12783/asc33/26077","url":null,"abstract":"High-fidelity progressive damage simulations of composite materials are important for advancements in damage tolerant design. We recently proposed a novel modeling approach for damage analysis of composite laminates, in which multi-layer structures are represented as individual plies connected through zero-Thickness cohesive interfaces. The model is developed in the framework of Isogeometric Analysis (IGA). By using Non-Uniform Rational B-Spline (NURBS) basis functions for representing geometries and discretizing the displacement field, IGA allows for a more direct connection between numerical simulation and CAD software. In addition, compared to traditional polynomial basis functions, NURBS functions allow for better representation of geometries and higher order inter-element continuity properties. The computational efficiency of the proposed modeling approach stems from the adoption of Kirchhoff-Love shell elements for the modeling of individual lamina. Intralaminar damage is introduced in the framework of continuum damage mechanics, in which a strain-softening damage model drives the degradation of material elastic properties. However, the use of local strain measures, in combination with strainsoftening degradation models, may lead to damage localization problems. These cause the governing equations to become ill-posed and their approximate solution to be highly mesh-sensitive. Our work aims to re-establish the objectivity with respect to the adopted discretization. We extend our analysis framework by introducing a smoothed strain field to re-place the local strain measures used in the damage model. Our approach builds on the Gradient-Enhanced Damage (GED) model and is specialized for the Kirchhoff-Love shell structural model. The smoothed strain field is obtained by solving an additional set of partial differential equations on each ply of the composite laminate. The GED model can be applied to smooth tensor-valued quantities, such as strains, on generic-shaped geometries in the three-dimensional space, including complex and curved aerospace structures modeled by means of shell elements. In this work, we propose numerical examples in order to illustrate the validity of the GED model.","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134618459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An important aspect of the design of composite structures is certification for damage tolerance. Current certification involves tests for low velocity impact (LVI) damage, and the residual compression strength after impact (CSAI). In this work, an adaptive fidelity shell (AFS) model is used to simulate this mutli-step LVI/CSAI process, improving previous LVI results. The two-step process is simulated to ensure that the damage is transferred correctly from one step (LVI) to the next (CSAI) correctly. Use of this model will enable efficient large-scale simulations of full structures with accurate estimations of damage and strength. The AFS model was used to simulate LVI and CSAI for two laminate stacking sequences from the ONR high fidelity database. The model shows promise, but further development is needed to fully capture damage processes seen in LVI/CSAI.
{"title":"Computationally Efficient Damage and Residual Strength Predictions using Progressive Damage Failure Analysis (PDFA) with an Enriched Shell Element","authors":"T. Goode, Mark McElroy, Nathan Sesar, M. Pankow","doi":"10.12783/ASC33/25908","DOIUrl":"https://doi.org/10.12783/ASC33/25908","url":null,"abstract":"An important aspect of the design of composite structures is certification for damage tolerance. Current certification involves tests for low velocity impact (LVI) damage, and the residual compression strength after impact (CSAI). In this work, an adaptive fidelity shell (AFS) model is used to simulate this mutli-step LVI/CSAI process, improving previous LVI results. The two-step process is simulated to ensure that the damage is transferred correctly from one step (LVI) to the next (CSAI) correctly. Use of this model will enable efficient large-scale simulations of full structures with accurate estimations of damage and strength. The AFS model was used to simulate LVI and CSAI for two laminate stacking sequences from the ONR high fidelity database. The model shows promise, but further development is needed to fully capture damage processes seen in LVI/CSAI.","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124771097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Most currently available material models for composites do not allow for permanent strain. For applications such as ballistic containment and energy absorption applications, this results in under predicting material performance. This study extends the Matzenmiller, Lubliner and Taylor (MLT) model, a continuum damage mechanics (CDM) based constitutive model for unidirectional composites, to 3D solid elements, and enhances it with permanent strain capability. The model was implemented into the commercially available finite element code LS-Dyna. The model was validated with 3-point bend experiment. It was then used to simulate ballistic impact tests of an aluminum projectile against a glass fiber composite plate. As shown in the results below, this provides significant improvement in prediction of material performance
目前大多数可用的复合材料模型都不考虑永久应变。对于诸如弹道遏制和能量吸收等应用，这将导致材料性能低于预测。本研究将基于连续损伤力学(CDM)的单向复合材料本构模型Matzenmiller, Lubliner and Taylor (MLT)模型扩展到三维实体单元，并增强了该模型的永久应变能力。该模型在市售有限元代码LS-Dyna中实现。通过三点弯曲实验对模型进行了验证。然后用它来模拟铝弹对玻璃纤维复合板的弹道冲击试验。如下图所示，这在预测材料性能方面提供了显著的改进
{"title":"3D Continuum Damage Mechanics Model with Permanent Strain","authors":"James D. Dorer, Xinran Xiao","doi":"10.12783/asc33/25981","DOIUrl":"https://doi.org/10.12783/asc33/25981","url":null,"abstract":"Most currently available material models for composites do not allow for permanent strain. For applications such as ballistic containment and energy absorption applications, this results in under predicting material performance. This study extends the Matzenmiller, Lubliner and Taylor (MLT) model, a continuum damage mechanics (CDM) based constitutive model for unidirectional composites, to 3D solid elements, and enhances it with permanent strain capability. The model was implemented into the commercially available finite element code LS-Dyna. The model was validated with 3-point bend experiment. It was then used to simulate ballistic impact tests of an aluminum projectile against a glass fiber composite plate. As shown in the results below, this provides significant improvement in prediction of material performance","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"233 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132042706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ping Wang, D. Gil, M. Pajon, B. Hernandez, Juliette Dubon, B. Boesl, S. Khizroev, B. Arkook, D. McDaniel
Adhesive bonding for composite structures offers multiple advantages over traditional fasteners such as reducing the weight, creating a more uniformly distributed stress state in the joint, and elimination of stress concentration factors due to joining. However, the strength of adhesive bonds can be reduced due to environmental exposure, contamination, mechanical damage and fatigue and assurances of long-term durability and bond strength are not available. Before adhesive bonding of composites can be used on primary structures, a method for guaranteeing the bonds strength must be developed. Due to magneto-electric principles, magneto-electric nanoparticles (MENs) can be used to detect minute changes of electric fields at the molecular level through detectable changes of the nanoparticles’ magnetization. As a result, when integrated into epoxy based adhesives, MENs are capable of detecting chemical or mechanical induced material imperfections at the molecular level. Current efforts are focused on developing a field tool that can be used to obtain magnetic signatures from doped adhesives similar to those obtained via laboratory scale equipment (vibrating sample magnetometer). To achieve similar sensitivities, FIU is investigating the use of a B-H looper system. In this approach, the MENs material is probed with a specifically designed setup that includes small electric coils wrapped around the sample. The coils are arranged into a noisecancellation configuration to measure the magnetic susceptibility of the sample under various conditions with a lock-in amplifier. With the goal to identify signature response characteristics of specific environmental and mechanical effects, various epoxy based adhesive samples were doped with 30 nm diameter MENs. Differences in magnetic signatures were observed between environmentally aged samples and baseline samples, demonstrating the viability of the B-H looper system as a bond inspection tool.
{"title":"Multifunctional MENs Doped Adhesives for Bond Quality Evaluation","authors":"Ping Wang, D. Gil, M. Pajon, B. Hernandez, Juliette Dubon, B. Boesl, S. Khizroev, B. Arkook, D. McDaniel","doi":"10.12783/ASC33/26106","DOIUrl":"https://doi.org/10.12783/ASC33/26106","url":null,"abstract":"Adhesive bonding for composite structures offers multiple advantages over traditional fasteners such as reducing the weight, creating a more uniformly distributed stress state in the joint, and elimination of stress concentration factors due to joining. However, the strength of adhesive bonds can be reduced due to environmental exposure, contamination, mechanical damage and fatigue and assurances of long-term durability and bond strength are not available. Before adhesive bonding of composites can be used on primary structures, a method for guaranteeing the bonds strength must be developed. Due to magneto-electric principles, magneto-electric nanoparticles (MENs) can be used to detect minute changes of electric fields at the molecular level through detectable changes of the nanoparticles’ magnetization. As a result, when integrated into epoxy based adhesives, MENs are capable of detecting chemical or mechanical induced material imperfections at the molecular level. Current efforts are focused on developing a field tool that can be used to obtain magnetic signatures from doped adhesives similar to those obtained via laboratory scale equipment (vibrating sample magnetometer). To achieve similar sensitivities, FIU is investigating the use of a B-H looper system. In this approach, the MENs material is probed with a specifically designed setup that includes small electric coils wrapped around the sample. The coils are arranged into a noisecancellation configuration to measure the magnetic susceptibility of the sample under various conditions with a lock-in amplifier. With the goal to identify signature response characteristics of specific environmental and mechanical effects, various epoxy based adhesive samples were doped with 30 nm diameter MENs. Differences in magnetic signatures were observed between environmentally aged samples and baseline samples, demonstrating the viability of the B-H looper system as a bond inspection tool.","PeriodicalId":337735,"journal":{"name":"American Society for Composites 2018","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129201584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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