Pub Date : 2023-10-18DOI: 10.1177/10996362231208745
Chris Fischer, Falk Hähnel, Klaus Wolf, Johannes Markmiller
Honeycomb cores made of phenol resin impregnated paper are widely used in sandwich structures of aircraft. Owing to the rather weak core material, this kind of sandwich is prone to a range of damages as a result of impact loading which may accidentally occur during operation. When employed in aircraft these structures have to be damage tolerant. This means barely visible damages have to be considered in the structural design process. In the standard design process for damage tolerant aircraft structures especially the effect of impacts has to be considered but is mostly investigated on unloaded sandwich components. However, aircraft structures are not completely stress free, even when the aircraft is in parking position. At least the structural weight will cause a permanent static preload. In the literature there are only few investigations dealing with the impact behaviour of preloaded honeycomb sandwich structures. In general, studies on composite structures have shown that tension preloads lead to higher structural impact resistance, while prestressing in compression reduces mechanical properties such as impact strength and stiffness of the structure. For this reason, a compression preload is considered as the more critical load case. In order to evaluate the effect of static compression preloads an experimental study on five different honeycomb sandwich configurations was conducted. The experimental investigations showed that even low preloads cause a higher structural damage area, which results in a lower residual strength of the structure. The results indicated that it is recommendable to consider structural compression preloads in the aircraft structural design process.
{"title":"Impact analysis of compression preloaded honeycomb sandwich structures","authors":"Chris Fischer, Falk Hähnel, Klaus Wolf, Johannes Markmiller","doi":"10.1177/10996362231208745","DOIUrl":"https://doi.org/10.1177/10996362231208745","url":null,"abstract":"Honeycomb cores made of phenol resin impregnated paper are widely used in sandwich structures of aircraft. Owing to the rather weak core material, this kind of sandwich is prone to a range of damages as a result of impact loading which may accidentally occur during operation. When employed in aircraft these structures have to be damage tolerant. This means barely visible damages have to be considered in the structural design process. In the standard design process for damage tolerant aircraft structures especially the effect of impacts has to be considered but is mostly investigated on unloaded sandwich components. However, aircraft structures are not completely stress free, even when the aircraft is in parking position. At least the structural weight will cause a permanent static preload. In the literature there are only few investigations dealing with the impact behaviour of preloaded honeycomb sandwich structures. In general, studies on composite structures have shown that tension preloads lead to higher structural impact resistance, while prestressing in compression reduces mechanical properties such as impact strength and stiffness of the structure. For this reason, a compression preload is considered as the more critical load case. In order to evaluate the effect of static compression preloads an experimental study on five different honeycomb sandwich configurations was conducted. The experimental investigations showed that even low preloads cause a higher structural damage area, which results in a lower residual strength of the structure. The results indicated that it is recommendable to consider structural compression preloads in the aircraft structural design process.","PeriodicalId":16977,"journal":{"name":"Journal of Sandwich Structures and Materials","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135883116","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}
Pub Date : 2023-10-17DOI: 10.1177/10996362231207876
Sergey V Kuznetsov
The analytical and geometrical conditions for the possible appearance of the infinite group velocity (IGV) points belonging to the dispersion curves of Lamb waves propagating in traction-free plates are studied by a combined method comprising Cauchy sextic formalism and the exponential fundamental matrix method. According to the obtained geometrical condition, the IGV corresponds to the coincidence of a tangent line to any of the dispersion curves with a straight line passing through the origin. The developed technique is demonstrated by applying to the analysis of Lamb wave dispersion in three-layered plates with a soft inner core.
{"title":"On infinite group velocity in composite plates","authors":"Sergey V Kuznetsov","doi":"10.1177/10996362231207876","DOIUrl":"https://doi.org/10.1177/10996362231207876","url":null,"abstract":"The analytical and geometrical conditions for the possible appearance of the infinite group velocity (IGV) points belonging to the dispersion curves of Lamb waves propagating in traction-free plates are studied by a combined method comprising Cauchy sextic formalism and the exponential fundamental matrix method. According to the obtained geometrical condition, the IGV corresponds to the coincidence of a tangent line to any of the dispersion curves with a straight line passing through the origin. The developed technique is demonstrated by applying to the analysis of Lamb wave dispersion in three-layered plates with a soft inner core.","PeriodicalId":16977,"journal":{"name":"Journal of Sandwich Structures and Materials","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136034313","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}
Pub Date : 2023-09-29DOI: 10.1177/10996362231203207
Joulia Salloum, Romain Léger, Hussein Chebbo, Loïc Daridon, Patrick Ienny
This paper aims to characterize the intrinsic mechanical behavior of an eco-friendly foam core used in sandwich materials dedicated to the maritime sector. A thorough understanding of intrinsic properties is essential for accurate dimensional structure characterization. The model setup is based on the choice of materials that meet the criteria of sustainable development, mechanical performance, and durability to promote ecological practices in the nautical industry. Experimental tests, instrumented by a digital image correlation technique, were carried out on two types of foams: polyvinyl chloride (PVC), which is the reference foam traditionally used in marine applications, and recycled polyethylene terephthalate (rPET), the substitute foam. The sample sizes recommended by compression test standards often lead to complex stress states that do not allow direct determination of the foam's intrinsic mechanical properties. Therefore, a finite element model updating method was required to identify the anisotropic elastic behavior of these two types of foams.
{"title":"A new methodology for the mechanical behavior analysis of polyvinyl chloride and recycled polyethylene terephthalate foams: Finite element model updating using mechanical field measurements","authors":"Joulia Salloum, Romain Léger, Hussein Chebbo, Loïc Daridon, Patrick Ienny","doi":"10.1177/10996362231203207","DOIUrl":"https://doi.org/10.1177/10996362231203207","url":null,"abstract":"This paper aims to characterize the intrinsic mechanical behavior of an eco-friendly foam core used in sandwich materials dedicated to the maritime sector. A thorough understanding of intrinsic properties is essential for accurate dimensional structure characterization. The model setup is based on the choice of materials that meet the criteria of sustainable development, mechanical performance, and durability to promote ecological practices in the nautical industry. Experimental tests, instrumented by a digital image correlation technique, were carried out on two types of foams: polyvinyl chloride (PVC), which is the reference foam traditionally used in marine applications, and recycled polyethylene terephthalate (rPET), the substitute foam. The sample sizes recommended by compression test standards often lead to complex stress states that do not allow direct determination of the foam's intrinsic mechanical properties. Therefore, a finite element model updating method was required to identify the anisotropic elastic behavior of these two types of foams.","PeriodicalId":16977,"journal":{"name":"Journal of Sandwich Structures and Materials","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135246075","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}
The structural optimization of Ti-alloy lattice structure formed by the superplastic forming/diffusion bonding (SPF/DB) process is a high-nonlinear problem with multiple design variables. The problem is solved in this research by introducing the modified Kriging response surface model based on structural mechanics analysis and the genetic algorithm into the optimization design of the Kagome structure. The comprehensive influence of the structural parameters on the shape and compressive strength of the structure is analyzed, and the optimized structural parameters are obtained. The SPF/DB forming and performance test of the optimized Kagome structure are carried out for verifying the accuracy of the model. The results show that the modified Kriging response surface model of the Kagome structure performs well in describing the relationships between the structural parameters and the simulation results, the average relative error of the predicted groove depth and compression strength are 2.4% and 4.5%, respectively. The specific compression strength and the specific compression modulus of the optimized Kagome structure are [Formula: see text] and [Formula: see text]. Based on the compression strength results calculated by the Kriging model, a new Ashby plot for the compressive strength as function of density is obtained.
{"title":"Structural optimization and experimental study on the Ti-alloy Kagome structure formed by the superplastic forming/diffusion bonding process","authors":"Dipeng Wu, Yong Wu, Minghe Chen, Ronglei Fan, Keming Yan, Wenchao Xiao","doi":"10.1177/10996362231203208","DOIUrl":"https://doi.org/10.1177/10996362231203208","url":null,"abstract":"The structural optimization of Ti-alloy lattice structure formed by the superplastic forming/diffusion bonding (SPF/DB) process is a high-nonlinear problem with multiple design variables. The problem is solved in this research by introducing the modified Kriging response surface model based on structural mechanics analysis and the genetic algorithm into the optimization design of the Kagome structure. The comprehensive influence of the structural parameters on the shape and compressive strength of the structure is analyzed, and the optimized structural parameters are obtained. The SPF/DB forming and performance test of the optimized Kagome structure are carried out for verifying the accuracy of the model. The results show that the modified Kriging response surface model of the Kagome structure performs well in describing the relationships between the structural parameters and the simulation results, the average relative error of the predicted groove depth and compression strength are 2.4% and 4.5%, respectively. The specific compression strength and the specific compression modulus of the optimized Kagome structure are [Formula: see text] and [Formula: see text]. Based on the compression strength results calculated by the Kriging model, a new Ashby plot for the compressive strength as function of density is obtained.","PeriodicalId":16977,"journal":{"name":"Journal of Sandwich Structures and Materials","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135815961","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}
Pub Date : 2023-09-08DOI: 10.1177/10996362231201880
Yanan Zhong, Yi Ren, Jijuan Zhang, Zhongfeng Zhang
Honeycomb panels manufactured from wood and paper materials promote a high-value utilization of wood resources. However, the poor mechanical properties and uncommon thicknesses (32 and 40 mm) of paper honeycomb panels limit their application and promotion in the panel furniture industry. Hence, numerous attempts have been made to develop high-strength and low-density wood sandwich composites for the frames and partitions of cabinet furniture. This paper describes a method for manufacturing lightweight sandwich panels (18 mm thickness) with auxetic cores, made of fast-growing poplar. The mechanical properties of the panels and the negative Poisson's ratio of the perforated sheet cores were determined by three-point bending and uniaxial compression tests. The lower density, higher modulus of elasticity, and bending strength suggest that the developed panel is a good substitute for traditional wood-based panels. A numerical model for panels in bending tests is proposed and validated against the experimental analysis results. These investigations facilitate further research into optimizing the sandwich panel structure and its applicability in the architectural and furniture industry.
{"title":"Wooden sandwich panels with auxetic core for furniture - experimental and numerical analysis","authors":"Yanan Zhong, Yi Ren, Jijuan Zhang, Zhongfeng Zhang","doi":"10.1177/10996362231201880","DOIUrl":"https://doi.org/10.1177/10996362231201880","url":null,"abstract":"Honeycomb panels manufactured from wood and paper materials promote a high-value utilization of wood resources. However, the poor mechanical properties and uncommon thicknesses (32 and 40 mm) of paper honeycomb panels limit their application and promotion in the panel furniture industry. Hence, numerous attempts have been made to develop high-strength and low-density wood sandwich composites for the frames and partitions of cabinet furniture. This paper describes a method for manufacturing lightweight sandwich panels (18 mm thickness) with auxetic cores, made of fast-growing poplar. The mechanical properties of the panels and the negative Poisson's ratio of the perforated sheet cores were determined by three-point bending and uniaxial compression tests. The lower density, higher modulus of elasticity, and bending strength suggest that the developed panel is a good substitute for traditional wood-based panels. A numerical model for panels in bending tests is proposed and validated against the experimental analysis results. These investigations facilitate further research into optimizing the sandwich panel structure and its applicability in the architectural and furniture industry.","PeriodicalId":16977,"journal":{"name":"Journal of Sandwich Structures and Materials","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136299847","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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