Journal of Composites Technology & Research最新文献

{"title":"A Design Procedure for Textile Composite Materials","authors":"Y. Gowayed, L. Barowski","doi":"10.1520/CTR10894J","DOIUrl":"https://doi.org/10.1520/CTR10894J","url":null,"abstract":"A design procedure for textile composite materials that is able to satisfy a set of target mechanical and thermal properties is presented. First the search space, within which a feasible solution may exist, is divided into discrete sections. These sections are sufficiently small so that material properties show little variation. In each section, the composite is defined as a set of yarn segments that possess certain relative volume fractions, initial elliptical cross-section shape, and spatial direction cosines. A unique solution is calculated using a stiffness averaging routine. Solutions are then compared and ranked based on a chosen selection criterion. The nature of the textile forming process is considered in the design approach. Proposed textile preforms are graphically constructed in 3-D space. The feasibility of changing the elliptical cross-section shape of yarns at different locations to fit within a high fiber-volume-fraction composite is investigated. A distortion factor is introduced to characterize the departure of the yarn cross-section from an initial elliptical shape. Two shapes for yarns cross-section, race track and boat-shape, are parametrically defined and used in the model.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"40 1","pages":"24-29"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79873778","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":"Computational Tracking of Composite Manufacturing with Fiber Preforms","authors":"B. Mauget, L. Minnetyan, C. Chamis","doi":"10.1520/CTR10998J","DOIUrl":"https://doi.org/10.1520/CTR10998J","url":null,"abstract":"The use of braided fiber preforms is a cost-effective process for the manufacturing of composite aircraft structures. For a rational design, it is necessary to predict the fiber orientations in the composite structure after molding. Whenever the manufacturing process requires the manipulation of fiber weaves, large strains and, therefore, significant changes in the fiber orientations occur due to the application of small traction. This drastically changes the mechanical properties of the final structure. To quantify this effect, a new method to simulate the large deformation behavior of fiber preforms has been developed and is presented. The method uses a laminate analogy model with very low stiffness matrix to compute the finite element properties. The assumptions are made that fibers do not elongate, the laminate is made of symmetrically woven fibers, and that, during a finite element step, the properties can be assumed constant. Based on these assumptions, a simple way to compute the fiber changes is proposed, as it is remarked that a box with fibers as its diagonal will deform into a box of different aspect ratio. The large displacement approach is valid since the properties depend on the global Poisson ratio computation that is proved accurate. The method is then demonstrated by an example, where a fiber weave preform is shaped over a mold. The resulting fiber orientations are analyzed to evaluate the effect of the manufacturing process on structure properties and durability. The advantage of the present method is further demonstrated by evaluating the damage tolerance of the composite structure via progressive fracture.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"3 1","pages":"254-258"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87904699","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":"Adaptation of the Iosipescu In-plane Shear Test Method for High Strength Textile Composites","authors":"W. Seneviratne, J. Tomblin","doi":"10.1520/CTR10999J","DOIUrl":"https://doi.org/10.1520/CTR10999J","url":null,"abstract":"In order to use the Iosipescu V-notch beam test for determining the in-plane shear strength of high strength 2D 2 × 2 biaxial braided composites, two modifications were made to the specimen geometry. First, they were tabbed to prevent buckling at the gage section and pinching of the specimen at grip sections. Tabbed specimens having gage sections of 0.50″, 0.35″, 0.188″ were studied. Also, to reduce the load required for failure, the shear area was decreased by deepening the V-notch. Failure modes of specimens having notch widths of 0.425″, 0.350″, 0.325″, and 0.300″ were examined. In this investigation, high toughness PR520 epoxy resin was selected to make panels by resin transfer molding (RTM). An initial study was conducted to find the best possible specimen geometry using ±45° braid. Then, both ±45° and ±60° braid angles were studied for the selected geometry. In order to investigate the cut direction effects on the ±60° braid in-plane shear modulus and the strength, the specimens were cut in both 0° and 90° directions of the panel. Tabbed specimens with a gage length of 0.188″ demonstrated the highest average shear strength. The notch width of 0.325″ produced acceptable failures. Thus, it was selected as the minimum notch width. Then, both ±45° and ±60° specimens having gage section of 0.188″ and notch width of 0.325″ were tested for shear properties. The tabs minimized the bending loads due to buckling and pinching of the specimens across the gage section. Modifications increased the in-plane shear strength by about 33–55% for ±45°. The 0° cut-direction specimens, which had ±30° fibers with respect to the loading path, had lower strength and modulus values than that of the 90° cut-direction specimens. Modulus results for ±60° specimens were close to analytical predictions regardless of the cut direction.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"41 1","pages":"259-266"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74995960","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":"Low degree of homogeneity due to phase shifts for woven composites","authors":"K. Woo, Y. Suh","doi":"10.1520/CTR10996J","DOIUrl":"https://doi.org/10.1520/CTR10996J","url":null,"abstract":"In this study, variation of effective properties due to fiber tow phase shifts was investigated for woven textile composites. Plain weave unit cells were modeled with randomly selected phase shifts. Effective properties were calculated using macro finite elements and the results were assessed statistically. It was found that the effective properties depended strongly on the tow phase shifts for thin plain weave composites. The variation in the effective modulus and Poisson's ratio was large, and it showed skewed distributions. As the number of layers increased, however, the average properties converged and the coefficient of variation decreased.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"11 1","pages":"239-246"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75622345","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":"Energy absorption of truncated Kevlar epoxy cones under off-axis loads","authors":"J. Knack, A. Vizzini","doi":"10.1520/CTR10997J","DOIUrl":"https://doi.org/10.1520/CTR10997J","url":null,"abstract":"A total of 27 Kevlar/epoxy truncated cones was manufactured and crushed under off-axis loads. Side loads were introduced by cutting the cones at angles relative to their central axes. The failure modes were observed, and the specific sustained crushing stresses were determined and compared against graphite/epoxy cones of the same lay-up and similar geometry. The Kevlar/epoxy cones exhibited significantly different failure modes than the graphite/epoxy cones. Specifically, the cones did not experience brittle fracture, and thus maintained structural integrity after crushing. The Kevlar/epoxy cones were less sensitive to the angle of the applied load than similar graphite/epoxy cones; however, the energy absorbed per unit mass is significantly lower. The role of specimen taper and load inclination is different than that for graphite/epoxy cones. In particular, 10° tapered cones overall had the best performance even under uniaxial loading conditions.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"16 1","pages":"247-253"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78266483","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":"A technique for measuring delamination crack tip behavior in composite materials inside a scanning electron microscope","authors":"I. Paris, R. Bennett, M. Mager, A. Poursartip","doi":"10.1520/CTR10551J","DOIUrl":"https://doi.org/10.1520/CTR10551J","url":null,"abstract":"This paper presents a technique for measuring the crack opening displacement (COD) and crack shear displacement (CSD) profiles at a delamination crack tip, and using them to evaluate the effective ‘local’ Mode I and Mode II strain energy release rates. These values can then be compared to the ‘global’ strain energy release rates calculated in the usual manner from the globally applied conditions using Linear Elastic Fracture Mechanics (LEFM). The fixture that has been developed can accommodate full size standard delamination specimens, which can be loaded to failure in Mode I, Mode II, and mixed mode inside a Scanning Electron Microscope (SEM). The globally applied conditions (loads and displacements) and the local crack tip displacements can be simultaneously recorded and compared. The specimen preparation, the data acquisition and test control system, and the image acquisition and analysis system are described in detail. As an example, the results for a Mode I test of a 24-layer unidirectional AS4/3501-6 laminate are presented here. The COD profiles have been measured for 10 load levels covering 3 crack lengths. A square root singularity was observed, for roughly 500 μm behind the crack tip. Furthermore, there is perfect agreement between the local and global strain energy release rates, indicating that the globally applied load is transmitted fully to the crack tip. These results, for a brittle material with no fiber bridging, demonstrate the validity of the technique. In future publications, we will apply the technique to study fiber bridging in Mode I loading, crack waviness effects under Mode II loading, mixed-mode loading, and other cases of interest.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"24 1","pages":"165-177"},"PeriodicalIF":0.0,"publicationDate":"2001-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82182784","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":"Strain Rate and Temperature Effects on the Mechanical Properties of an E-Glass/Vinyl Ester Composite System","authors":"J. South, K. Reifsnider, S. Case","doi":"10.1520/CTR10553J","DOIUrl":"https://doi.org/10.1520/CTR10553J","url":null,"abstract":"The need exists for a failure time schema to predict composite component lifetimes from quasi-static to dynamic strain rates. Models need to incorporate temperature, loading rate, and the time to failure of the composite components. An approach to describe the effects of strain rate and temperature on the mechanical properties of an E-glass/vinyl ester composite system is presented and verified with experimental data. A representation of the time to failure of the composite was constructed using the Monkmann-Grant equation, relating the applied steady state strain rate and the time to failure. Strain rates of 10 -6 to 1.6 s -1 were achieved and experiments were conducted at room temperature, 80 and 120°C. It was found that the composite system exhibited nearly a constant strain to failure over the applied rates and temperatures. The test data verified an approach to a failure time estimation scheme for steady state strain rate utilizing the Monkmann-Grant approach.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"18 1","pages":"189-196"},"PeriodicalIF":0.0,"publicationDate":"2001-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77995860","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":"Shakedown Limits for a Metal Matrix Composite","authors":"A. Ponter, K. F. Carter, J. Duggan","doi":"10.1520/CTR10554J","DOIUrl":"https://doi.org/10.1520/CTR10554J","url":null,"abstract":"The paper discusses a method for the evaluation of the yield values of a metal matrix composite material when subjected to a variation in temperature. A direct shakedown analysis method is described which produces a shakedown stress value as a result of a sequence of incompressible linear solutions with a spatially varying modulus. The process converges to the minimum upper bound associated with the class of displacement fields when implemented in a finite element method (Ponter and Carter [1,2]). The solutions for an Aluminum/alumina system loaded in a direction perpendicular to the direction of the fibers demonstrate the high sensitivity of this material to fluctuations in temperature. Simple approximate equations for strength values are presented in terms of nondimensional variables.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"19 1","pages":"197-204"},"PeriodicalIF":0.0,"publicationDate":"2001-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81817685","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":"Interlaminar Deformation Along the Cylindrical Surface of a Hole in Laminated Composites—Experimental Analysis by Moiré Interferometry","authors":"D. Mollenhauer, K. Reifsnider","doi":"10.1520/CTR10552J","DOIUrl":"https://doi.org/10.1520/CTR10552J","url":null,"abstract":"The deformation along cylindrical surfaces of holes in tensile-loaded specimens was measured using new moire interferometry techniques. The techniques were developed and validated using an isotropic, homogeneous aluminum specimen. Two composite tensile specimens, fabricated from IM7/5250-4 pre-preg with ply lay-ups of [ 0 ° 4 ∕ 90 ° 4 ] 3 s and [ + 30 ° 2 ∕ − 30 ° 2 ∕ 90 ° 4 ] 3 s , were then examined using the new techniques. Circumferential and thickness direction displacement fringe patterns (each 3° wide) were assembled into 90°-wide mosaics around the hole periphery for both composite specimens. Distributions of strain were calculated with high confidence on a sub-ply basis at selected angular locations. The measured strain behavior was complex. Ply-by-ply trends were revealed. Large ply-related variations in the circumferential strain were observed at certain angular locations around the periphery of the holes in both composites. Extremely large ply-by-ply variations of the shear strain were also documented in both composites. Peak values of shear strain approached 30 times the applied far-field axial strain. Residual viscoelastic shearing strains were recorded in regions of large load-induced shearing strains. Large ply-group related variations in the thickness direction strain were observed in the [+30°, were then examined using the new techniques. Circumferential and thickness direction displacement fringe patterns (each 3° wide) were assembled into 90°-wide mosaics around the hole periphery for both composite specimens. Distributions of strain were calculated with high confidence on a sub-ply basis at selected angular locations. The measured strain behavior was complex. Ply-by-ply trends were revealed. Large ply-related variations in the circumferential strain were observed at certain angular locations around the periphery of the holes in both composites. Extremely large ply-by-ply variations of the shear strain were also documented in both composites. Peak values of shear strain approached 30 times the applied far-field axial strain. Residual viscoelastic shearing strains were recorded in regions of large load-induced shearing strains. Large ply-group related variations in the thickness direction strain were observed in the [ + 30 ° 2 ∕ − 30 ° 2 ∕ 90 ° 4 ] 3 s specimen. An important large-scale trend was observed in which the thickness direction strain tended to be more tensile near the outside faces of the laminate than near the mid-ply region.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"50 1","pages":"178-188"},"PeriodicalIF":0.0,"publicationDate":"2001-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75954514","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":"Effect of Twisting on Tensile Failure of Impregnated Yarns with Broken Filaments","authors":"N. Naik, Ishe Mudzingwa, M. Singh","doi":"10.1520/CTR10556J","DOIUrl":"https://doi.org/10.1520/CTR10556J","url":null,"abstract":"The tensile strength of impregnated strand/unidirectional composite depends on many factors including the strength of the interface. Recent efforts in trying to increase the strength of composites have been directed towards increasing the strength of the interface through fiber surface treatment and better resin systems that give better interfacial shear strength. However, the role of frictional forces and analysis of twisted impregnated yarns have largely been ignored. Twisted geometry gives rise to lateral pressure that contributes to the frictional shear stress; therefore, for a twisted yarn, interfacial shear strength would be higher than that of a impregnated strand/unidirectional composite. Twisted yarns have the obvious disadvantage that their unidirectional strength suffers because of fiber obliquity. This work examines the effect of the lateral pressure on the tensile strength of twisted yarns with broken filaments. Studies have been carried out on both the helical wound impregnated yarns and helical twisted impregnated yarns.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"25 1","pages":"225-234"},"PeriodicalIF":0.0,"publicationDate":"2001-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74930527","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}