Pub Date : 2023-04-17DOI: 10.1177/10996362231169982
Chengyu Guan, Zi-Jia Tang, Fei Zhao, Zhiyong Yang, Huimin Li
A homogenization method for the vibration analysis of periodic sandwich panels is presented. Periodic boundary conditions are applied to a representative volume element (RVE) of the structures. The complex responses of the RVE under eight sinusoidal excitations are calculated and the complex stiffness matrix of the sandwich panels is obtained by the direct-solution steady-state dynamic analysis (DSDA) using the finite element method (FEM) in the frequency domain. Based on equivalent single-layer (ESL) theory and finite element-modal strain energy (FE-MSE) method, the natural frequencies, the mode shapes and the loss factors of the structures are obtained by shell models. The effectiveness of the homogenization method is validated by using pyramidal lattice truss sandwich panels made of carbon fiber reinforced plastics (CFRP). The results obtained by the homogenization method are compared with those obtained by experiments and solid models. The effects of the number of cells and damping layers are discussed.
{"title":"A homogenization method for natural frequencies and damping analysis of composite pyramidal lattice truss sandwich structures based on representative volume elements","authors":"Chengyu Guan, Zi-Jia Tang, Fei Zhao, Zhiyong Yang, Huimin Li","doi":"10.1177/10996362231169982","DOIUrl":"https://doi.org/10.1177/10996362231169982","url":null,"abstract":"A homogenization method for the vibration analysis of periodic sandwich panels is presented. Periodic boundary conditions are applied to a representative volume element (RVE) of the structures. The complex responses of the RVE under eight sinusoidal excitations are calculated and the complex stiffness matrix of the sandwich panels is obtained by the direct-solution steady-state dynamic analysis (DSDA) using the finite element method (FEM) in the frequency domain. Based on equivalent single-layer (ESL) theory and finite element-modal strain energy (FE-MSE) method, the natural frequencies, the mode shapes and the loss factors of the structures are obtained by shell models. The effectiveness of the homogenization method is validated by using pyramidal lattice truss sandwich panels made of carbon fiber reinforced plastics (CFRP). The results obtained by the homogenization method are compared with those obtained by experiments and solid models. The effects of the number of cells and damping layers are discussed.","PeriodicalId":17215,"journal":{"name":"Journal of Sandwich Structures & Materials","volume":"127 1","pages":"572 - 590"},"PeriodicalIF":3.9,"publicationDate":"2023-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76610578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-07DOI: 10.1177/10996362231169976
Lijun Ji, Weilin Liu, Wensheng Gong, Xiang Qin, Lingling Liu, Liping Luo
Micron-scale grid-shaped, V-shaped and U-shaped corrugated sandwich structures are fabricated by 3D printing technology and present different mechanical properties from those made by traditional method. Their peak stresses and elastic moduli could be fitted to cubic functions. The compression performance of the multilayer grid-shaped sandwich can be determined by the relative mechanical strength of layers. Adding a layer on a grid-shaped sandwich has no significant influence on the peak stress, but can enhance the elastic modulus by about 60.9 MPa. The deformation modes of multilayer V-shaped and U-shaped sandwiches can be determined by the load carrying path and the relative mechanical properties between interlayers and cores. The elastic modulus of V-shaped sandwich is enhanced with the increase of layer number, while the elastic modulus of U-shaped sandwich decreases with the increase of layer number. The peak stress and the elastic modulus of a four-layer V-shaped sandwich can reach 9.85 MPa and 261.09 MPa, and those of a four-layer U-shaped sandwich can reach 4.79 MPa and 119.18 MPa. The result reveals the principles that the reduced structural size and suppressed debonding, the structures and the load carrying path, and materials, influence the failure mode and mechanical properties of the corrugated sandwiches. Graphical Abstract
{"title":"The compressive performances of 3D-printed micron-size corrugated sandwich structures","authors":"Lijun Ji, Weilin Liu, Wensheng Gong, Xiang Qin, Lingling Liu, Liping Luo","doi":"10.1177/10996362231169976","DOIUrl":"https://doi.org/10.1177/10996362231169976","url":null,"abstract":"Micron-scale grid-shaped, V-shaped and U-shaped corrugated sandwich structures are fabricated by 3D printing technology and present different mechanical properties from those made by traditional method. Their peak stresses and elastic moduli could be fitted to cubic functions. The compression performance of the multilayer grid-shaped sandwich can be determined by the relative mechanical strength of layers. Adding a layer on a grid-shaped sandwich has no significant influence on the peak stress, but can enhance the elastic modulus by about 60.9 MPa. The deformation modes of multilayer V-shaped and U-shaped sandwiches can be determined by the load carrying path and the relative mechanical properties between interlayers and cores. The elastic modulus of V-shaped sandwich is enhanced with the increase of layer number, while the elastic modulus of U-shaped sandwich decreases with the increase of layer number. The peak stress and the elastic modulus of a four-layer V-shaped sandwich can reach 9.85 MPa and 261.09 MPa, and those of a four-layer U-shaped sandwich can reach 4.79 MPa and 119.18 MPa. The result reveals the principles that the reduced structural size and suppressed debonding, the structures and the load carrying path, and materials, influence the failure mode and mechanical properties of the corrugated sandwiches. Graphical Abstract","PeriodicalId":17215,"journal":{"name":"Journal of Sandwich Structures & Materials","volume":"54 1","pages":"555 - 571"},"PeriodicalIF":3.9,"publicationDate":"2023-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85816637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-06DOI: 10.1177/10996362231159925
K. Naresh, Ruzanna Aziz Alia, W. Cantwell, R. Umer, K. Khan
This study presents the findings of an investigation into the effect of varying the thickness of a carbon/epoxy face sheet of a Nomex honeycomb sandwich panel on its the flexural properties. The thickness (hs) of the face sheet was varied by increasing the number of plies from one 0.25 mm thick layer to eight such layers, giving a total nominal thickness of 2.0 mm, whilst maintaining a constant thickness of the core. The flexural properties of the sandwich panels were investigated through a series of three- and four-point bending tests. A particular focus was on identifying changes in the failure mode with increasing face sheet thickness. The flexural properties of the sandwich panels were predicted using sandwich beam theory, where the deviation from the experimental values was shown to be less than 13%. A two parameter Weibull distribution model was used to predict the maximum flexural load using an analysis of variance (ANOVA) tool and an excellent level of correlation was observed with the experimental values. The difference between the predicted maximum load values and the experimental results was below 5% in all cases. A brittle mode of failure was observed in the thickest panel. The sandwich panel based on 1.5 mm thick face sheet was identified as being the most appropriate design, both in terms of strength and stiffness.
{"title":"Influence of face sheet thickness on flexural strength characteristics of carbon/epoxy/Nomex honeycomb sandwich panels","authors":"K. Naresh, Ruzanna Aziz Alia, W. Cantwell, R. Umer, K. Khan","doi":"10.1177/10996362231159925","DOIUrl":"https://doi.org/10.1177/10996362231159925","url":null,"abstract":"This study presents the findings of an investigation into the effect of varying the thickness of a carbon/epoxy face sheet of a Nomex honeycomb sandwich panel on its the flexural properties. The thickness (hs) of the face sheet was varied by increasing the number of plies from one 0.25 mm thick layer to eight such layers, giving a total nominal thickness of 2.0 mm, whilst maintaining a constant thickness of the core. The flexural properties of the sandwich panels were investigated through a series of three- and four-point bending tests. A particular focus was on identifying changes in the failure mode with increasing face sheet thickness. The flexural properties of the sandwich panels were predicted using sandwich beam theory, where the deviation from the experimental values was shown to be less than 13%. A two parameter Weibull distribution model was used to predict the maximum flexural load using an analysis of variance (ANOVA) tool and an excellent level of correlation was observed with the experimental values. The difference between the predicted maximum load values and the experimental results was below 5% in all cases. A brittle mode of failure was observed in the thickest panel. The sandwich panel based on 1.5 mm thick face sheet was identified as being the most appropriate design, both in terms of strength and stiffness.","PeriodicalId":17215,"journal":{"name":"Journal of Sandwich Structures & Materials","volume":"32 1","pages":"537 - 554"},"PeriodicalIF":3.9,"publicationDate":"2023-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80755000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-24DOI: 10.1177/10996362231159664
M. Iftimiciuc, Arne Derluyn, J. Pflug, D. Vandepitte
Honeycomb cores are used extensively in different sectors of industry to build advanced lightweight structures which take advantage of high stiffness-to-weight and strength-to-weight ratios. To further increase their mechanical properties, structural hierarchy is considered already from a conceptual point of view. It is proven to be highly effective in enhancing mechanical performance in different loading scenarios but affordable realisation of practical applications remains limited. The present study focuses on the out-of-plane compressive behaviour of a novel hierarchical sandwich honeycomb core with an emphasis on compressive strength, both in virtual and in experimental testing. The finite element model is validated for through-the-thickness compressive loading by physical experiments and it can subsequently be used for further structural optimization. The paper concludes with a comparison between the proposed hierarchical structure and conventional expanded honeycombs. The performance analysis highlights the advantages of the introduction of structural hierarchy to the state-of-the art honeycomb and it shows a high potential for the use in the construction of sandwich panels and parts.
{"title":"Out-of-plane compression mechanism of a novel hierarchical sandwich honeycomb core","authors":"M. Iftimiciuc, Arne Derluyn, J. Pflug, D. Vandepitte","doi":"10.1177/10996362231159664","DOIUrl":"https://doi.org/10.1177/10996362231159664","url":null,"abstract":"Honeycomb cores are used extensively in different sectors of industry to build advanced lightweight structures which take advantage of high stiffness-to-weight and strength-to-weight ratios. To further increase their mechanical properties, structural hierarchy is considered already from a conceptual point of view. It is proven to be highly effective in enhancing mechanical performance in different loading scenarios but affordable realisation of practical applications remains limited. The present study focuses on the out-of-plane compressive behaviour of a novel hierarchical sandwich honeycomb core with an emphasis on compressive strength, both in virtual and in experimental testing. The finite element model is validated for through-the-thickness compressive loading by physical experiments and it can subsequently be used for further structural optimization. The paper concludes with a comparison between the proposed hierarchical structure and conventional expanded honeycombs. The performance analysis highlights the advantages of the introduction of structural hierarchy to the state-of-the art honeycomb and it shows a high potential for the use in the construction of sandwich panels and parts.","PeriodicalId":17215,"journal":{"name":"Journal of Sandwich Structures & Materials","volume":"99 4 1","pages":"518 - 536"},"PeriodicalIF":3.9,"publicationDate":"2023-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75586047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-22DOI: 10.1177/10996362231159185
Zeyu Dong, Weikun Chen, O. Saito, Y. Okabe
Detecting disbonds in honeycomb sandwich structures using ultrasonics is challenging due to the complex wave propagation. This paper investigates the method for disbond quantification in honeycomb sandwich structures using laser ultrasonics. In the experiments on an aluminum specimen, the detection frequency range was determined by the local defect resonance (LDR) in the disbond regions. The energy maps of bandpass wavefields identified the locations of disbonds. To improve the results, a frequency-wavenumber analysis of the wavefields was performed. The wavenumber spectra were reconstructed by wavenumber filtering to strengthen the outline components for quantifying disbonds. Local cross-correlation (LCC) was proposed to show the outlines of disbonds and honeycomb cells, whose results agreed well with the X-ray imaging. Moreover, LCC could also quantify a disbond in the composite honeycomb sandwich structure. Consequently, combining energy maps and LCC results can effectively detect the locations and sizes of disbonds in honeycomb sandwich structures.
{"title":"Disbond detection of honeycomb sandwich structure through laser ultrasonics using signal energy map and local cross-correlation","authors":"Zeyu Dong, Weikun Chen, O. Saito, Y. Okabe","doi":"10.1177/10996362231159185","DOIUrl":"https://doi.org/10.1177/10996362231159185","url":null,"abstract":"Detecting disbonds in honeycomb sandwich structures using ultrasonics is challenging due to the complex wave propagation. This paper investigates the method for disbond quantification in honeycomb sandwich structures using laser ultrasonics. In the experiments on an aluminum specimen, the detection frequency range was determined by the local defect resonance (LDR) in the disbond regions. The energy maps of bandpass wavefields identified the locations of disbonds. To improve the results, a frequency-wavenumber analysis of the wavefields was performed. The wavenumber spectra were reconstructed by wavenumber filtering to strengthen the outline components for quantifying disbonds. Local cross-correlation (LCC) was proposed to show the outlines of disbonds and honeycomb cells, whose results agreed well with the X-ray imaging. Moreover, LCC could also quantify a disbond in the composite honeycomb sandwich structure. Consequently, combining energy maps and LCC results can effectively detect the locations and sizes of disbonds in honeycomb sandwich structures.","PeriodicalId":17215,"journal":{"name":"Journal of Sandwich Structures & Materials","volume":"83 1","pages":"501 - 517"},"PeriodicalIF":3.9,"publicationDate":"2023-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78251817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-20DOI: 10.1177/10996362231158599
Milad Hosseinkhani, Hamed Ghavami, M. Haghighi‐Yazdi, M. Mosavi Mashhadi, M. Safarabadi
This study investigates the effect of viscoelastic properties in the numerical modeling of foam-filled sandwich panels when their composite facesheets are exposed to low-velocity impact loading. A finite element (FE) model is developed using the software package of ABAQUS and used to investigate the effect of both considering and ignoring the time-dependent behavior of composite laminate facesheets as well as the foam core. Material constitutive equations, damage characteristics, and failure modes are defined in a FORTRAN user-subroutine VUMAT. To characterize the material behavior of both polyurethane foam and glass/epoxy composite material, a set of experimental tests are conducted under compression, tension, and stress relaxation modes. To validate the numerical results, low-velocity impact tests at two energy levels of 9.81 and 17 joules are carried out on sandwich panels with foam core. The results of numerical simulations are found to be in good agreement with the experimental test results. It is shown that ignoring the viscoelastic properties in the composite laminate and the foam core can lead to deviations of up to 7% and 25%, respectively, from experimental results. The analysis reveals that, ignoring the viscoelastic behavior along the fiber-direction in the composite facesheets does no change the results considerably. The viscoelastic properties perpendicular to the fibers, however, has a more noticeable effect on the results due to the prevalence of the properties of the polymeric resin in that direction.
{"title":"Investigation of viscoelastic properties in composite sandwich panels subjected to low-velocity impact: Experimental and numerical approaches","authors":"Milad Hosseinkhani, Hamed Ghavami, M. Haghighi‐Yazdi, M. Mosavi Mashhadi, M. Safarabadi","doi":"10.1177/10996362231158599","DOIUrl":"https://doi.org/10.1177/10996362231158599","url":null,"abstract":"This study investigates the effect of viscoelastic properties in the numerical modeling of foam-filled sandwich panels when their composite facesheets are exposed to low-velocity impact loading. A finite element (FE) model is developed using the software package of ABAQUS and used to investigate the effect of both considering and ignoring the time-dependent behavior of composite laminate facesheets as well as the foam core. Material constitutive equations, damage characteristics, and failure modes are defined in a FORTRAN user-subroutine VUMAT. To characterize the material behavior of both polyurethane foam and glass/epoxy composite material, a set of experimental tests are conducted under compression, tension, and stress relaxation modes. To validate the numerical results, low-velocity impact tests at two energy levels of 9.81 and 17 joules are carried out on sandwich panels with foam core. The results of numerical simulations are found to be in good agreement with the experimental test results. It is shown that ignoring the viscoelastic properties in the composite laminate and the foam core can lead to deviations of up to 7% and 25%, respectively, from experimental results. The analysis reveals that, ignoring the viscoelastic behavior along the fiber-direction in the composite facesheets does no change the results considerably. The viscoelastic properties perpendicular to the fibers, however, has a more noticeable effect on the results due to the prevalence of the properties of the polymeric resin in that direction.","PeriodicalId":17215,"journal":{"name":"Journal of Sandwich Structures & Materials","volume":"25 1","pages":"478 - 498"},"PeriodicalIF":3.9,"publicationDate":"2023-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49333802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-12DOI: 10.1177/10996362231151456
Zhongwei Zhang, Weijie Li, Yuping Yang, Hao Wu
As for high resolution satellite application field, novel C/SiC honeycomb sandwich structure is the first to propose and develop on account of such many attractive properties as excellent ultrahigh dimensional stability in thermal and moisture coupling environment, lightweight and high load-bearing. Three types of C/SiC honeycomb sandwich structures were fabricated for the first time as opto-mechanical structure in satellite. The innovative interlayer-crosslinking method to weave the continuous carbon fiber fabric of honeycomb core was proposed. The compressive properties of novel C/SiC honeycomb sandwich structures were investigated. Meanwhile, the damage mechanism for sandwich structures were analyzed by non-destructive testing. The results showed that the innovative fabrication processing possessed the capability to prepare high quality C/SiC honeycomb, which was shown from the volume and distribution of pores in the X-ray tomography. The compression modulus and strength of the C/SiC honeycomb reached 927 MPa and 10.76 MPa, and showed better rigidity and higher strength compared with classical honeycombs. Two main types of cracks wall were found in the C/SiC honeycomb, i.e., the horizontal ones in the wall with t thickness and the inclined ones in the wall with 2t thickness. The outstanding compressive performance was attributed to the high mechanical property of ceramic-matrix composite with fiber pull-out mechanism. The exceptional lightweight capacity was inherited from the low bulk density of honeycomb structure ranged from 0.08 g/cm3 to 0.15 g/cm3. This study can help for the development of lightweight materials for opto-mechanical structure in aerospace optical remote sensing technology.
{"title":"Fabrication and compressive performance of novel lightweight C/SiC honeycomb for ultrahigh stability structures","authors":"Zhongwei Zhang, Weijie Li, Yuping Yang, Hao Wu","doi":"10.1177/10996362231151456","DOIUrl":"https://doi.org/10.1177/10996362231151456","url":null,"abstract":"As for high resolution satellite application field, novel C/SiC honeycomb sandwich structure is the first to propose and develop on account of such many attractive properties as excellent ultrahigh dimensional stability in thermal and moisture coupling environment, lightweight and high load-bearing. Three types of C/SiC honeycomb sandwich structures were fabricated for the first time as opto-mechanical structure in satellite. The innovative interlayer-crosslinking method to weave the continuous carbon fiber fabric of honeycomb core was proposed. The compressive properties of novel C/SiC honeycomb sandwich structures were investigated. Meanwhile, the damage mechanism for sandwich structures were analyzed by non-destructive testing. The results showed that the innovative fabrication processing possessed the capability to prepare high quality C/SiC honeycomb, which was shown from the volume and distribution of pores in the X-ray tomography. The compression modulus and strength of the C/SiC honeycomb reached 927 MPa and 10.76 MPa, and showed better rigidity and higher strength compared with classical honeycombs. Two main types of cracks wall were found in the C/SiC honeycomb, i.e., the horizontal ones in the wall with t thickness and the inclined ones in the wall with 2t thickness. The outstanding compressive performance was attributed to the high mechanical property of ceramic-matrix composite with fiber pull-out mechanism. The exceptional lightweight capacity was inherited from the low bulk density of honeycomb structure ranged from 0.08 g/cm3 to 0.15 g/cm3. This study can help for the development of lightweight materials for opto-mechanical structure in aerospace optical remote sensing technology.","PeriodicalId":17215,"journal":{"name":"Journal of Sandwich Structures & Materials","volume":"25 1","pages":"462 - 477"},"PeriodicalIF":3.9,"publicationDate":"2023-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46511536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-09DOI: 10.1177/10996362231151454
Anis Hamrouni, J. Rebiere, A. El Mahi, M. Beyaoui, M. Haddar
This work presents the results of experimental and numerical analyses of the static properties of architectural cores and the dynamic behavior of sandwich structures made with an auxetic or non-auxetic core. Three architectural cores have been studied which are re-entrant, rectangular and hexagonal honeycombs. Each configuration was produced with four relative densities depending on the number of cells in the width of the specimens. The specimens were made with additive manufacturing technology. The material used to make the specimens was polylactic acid with flax fibers. Several tensile tests were carried out on the architectural cores to analyze and understand the influence of the topology and the density of the core on the Poisson’s ratio and the Young’s modulus of these architectural structures. Then, vibration tests were carried out on the cores and the sandwich structures. The objective was to study the influence of these structures and their densities on the dynamic properties of sandwiches. The structural Poisson’s ratio shows a sensitive behavior to the core topology and density.
{"title":"Experimental and finite element analyses of a 3D printed sandwich with an auxetic or non-auxetic core","authors":"Anis Hamrouni, J. Rebiere, A. El Mahi, M. Beyaoui, M. Haddar","doi":"10.1177/10996362231151454","DOIUrl":"https://doi.org/10.1177/10996362231151454","url":null,"abstract":"This work presents the results of experimental and numerical analyses of the static properties of architectural cores and the dynamic behavior of sandwich structures made with an auxetic or non-auxetic core. Three architectural cores have been studied which are re-entrant, rectangular and hexagonal honeycombs. Each configuration was produced with four relative densities depending on the number of cells in the width of the specimens. The specimens were made with additive manufacturing technology. The material used to make the specimens was polylactic acid with flax fibers. Several tensile tests were carried out on the architectural cores to analyze and understand the influence of the topology and the density of the core on the Poisson’s ratio and the Young’s modulus of these architectural structures. Then, vibration tests were carried out on the cores and the sandwich structures. The objective was to study the influence of these structures and their densities on the dynamic properties of sandwiches. The structural Poisson’s ratio shows a sensitive behavior to the core topology and density.","PeriodicalId":17215,"journal":{"name":"Journal of Sandwich Structures & Materials","volume":"25 1","pages":"426 - 444"},"PeriodicalIF":3.9,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45170457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-07DOI: 10.1177/10996362231151453
M. Stanfield, Bradley Kuramoto, D. Adams
An open-hole flexure test method has been developed to assess the notch sensitivity of sandwich composites under flexural loading. This test method, recently standardized as ASTM D8453, utilizes the current long beam four-point flexure fixture with the addition of a centrally-located open through-hole in the standard specimen. Previous research has identified an open-hole diameter that minimized finite-width effects while producing a statistically significant reduction in strength. Finite element analyses focused on quantifying interaction between the open-hole stress concentration and the load span length, hole location tolerance, and misalignment of the specimen and fixture. The effect of non-linear geometry due to large deflection was investigated and limits prescribed for linear geometry assumptions to remain valid. The sandwich configurations investigated consisted of a Nomex honeycomb core and carbon/epoxy facesheet laminates with a range of material orthotropy ratios. A series of mechanical tests were performed to evaluate the proposed specimen design, and the existing test fixture and procedure. The first set of experiments were performed to assess the notched strength sensitivity to the load span length. A second set of experiments assessed the effect of different core densities and thicknesses.
{"title":"Development and evaluation of the sandwich open-hole flexure test","authors":"M. Stanfield, Bradley Kuramoto, D. Adams","doi":"10.1177/10996362231151453","DOIUrl":"https://doi.org/10.1177/10996362231151453","url":null,"abstract":"An open-hole flexure test method has been developed to assess the notch sensitivity of sandwich composites under flexural loading. This test method, recently standardized as ASTM D8453, utilizes the current long beam four-point flexure fixture with the addition of a centrally-located open through-hole in the standard specimen. Previous research has identified an open-hole diameter that minimized finite-width effects while producing a statistically significant reduction in strength. Finite element analyses focused on quantifying interaction between the open-hole stress concentration and the load span length, hole location tolerance, and misalignment of the specimen and fixture. The effect of non-linear geometry due to large deflection was investigated and limits prescribed for linear geometry assumptions to remain valid. The sandwich configurations investigated consisted of a Nomex honeycomb core and carbon/epoxy facesheet laminates with a range of material orthotropy ratios. A series of mechanical tests were performed to evaluate the proposed specimen design, and the existing test fixture and procedure. The first set of experiments were performed to assess the notched strength sensitivity to the load span length. A second set of experiments assessed the effect of different core densities and thicknesses.","PeriodicalId":17215,"journal":{"name":"Journal of Sandwich Structures & Materials","volume":"25 1","pages":"445 - 461"},"PeriodicalIF":3.9,"publicationDate":"2023-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45022728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-03DOI: 10.1177/10996362221148493
M. Shakir, M. Talha, D. Hui, W. Gao
The present study investigates the influence of initial geometric imperfections on large amplitude vibration of shallow sandwich shells with functionally graded graphene nanoplatelets reinforced porous (FG-GNPRP) core embedded between two aluminium facets. The aluminium core is reinforced with graphene nano-platelets (GNP) and the effective properties such as elastic modulus, and mass density, etc. are estimated using Halpin-Tsai and Voigt models, respectively. The continuous functions are adopted to accomplish micro-structural gradation while creating pores which imparts the variation in material properties along thickness direction. The nonlinear governing equations based on higher order shear deformation theory and Sander’s approximation are derived using variational approach. The nonlinearity is introduced in von-Kármán sense and various imperfection modes such as sine, global and local types are considered in transverse direction. The nonlinear results are accessed using finite element method in conjunction with direct iterative technique. The influence of porosity, GNP weight fraction, imperfection amplitude, thickness, side, and radius ratios on the vibration response of the sandwich shells is explored in detail.
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