Journal of Composites Technology & Research最新文献

{"title":"Three-Dimensional Effect in the Prediction of Flange Delamination in Composite Skin-Stringer Pull-off Specimens","authors":"Jian Li","doi":"10.1520/CTR10568J","DOIUrl":"https://doi.org/10.1520/CTR10568J","url":null,"abstract":"Three-dimensional finite element modeling was used to analyze the delamination between the stiffener flange and the skin of a typical pull-off specimen representing a section of a stiffened skin panel. The finite element analysis results were used to calculate the total strain energy release rate and its Mode I, Mode II, and Mode III components along the delamination front through the width of the pull-off specimen. Three-dimensional modeling makes it possible to represent ply-by-ply lamina properties in the model. However, the ply-by-ply approach should not be used for highly angle ply laminates because of the strong transverse effect from adjacent plies. A smeared properties approach is more robust for the strain energy release rate analysis of delamination between ±45-degree angle ply laminates. The three-dimensional analysis indicates that delamination failure between the stiffener flange and the skin is dominated by Mode I and Mode II delamination modes. The three-dimensional analysis predicts delamination growth from the interior of the pull-off specimen width, and higher pull-off load is required to grow the delamination close to the free edges. The delamination initiation load along the interior of the pull-off specimen width does not change with the change of the width of the pull-off specimen. However, the wider specimen has stronger free edge effects than the narrower specimen. The lay-up of the skin and the flange can have significant effect on the delamination initiation load. Stiffening the skin and maintaining the compliant flange will increase the delamination initiation load.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"1 1","pages":"180-187"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80154425","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":"Adhesive Bonding of Composite Structures—Progress to Date and Some Remaining Challenges","authors":"L. Hart-Smith","doi":"10.1520/CTR10566J","DOIUrl":"https://doi.org/10.1520/CTR10566J","url":null,"abstract":"The purpose of this paper is to describe and explain some highlights in the history of adhesive bonding of fibrous composite structures. Successes are described, along with opportunities to do better in future. The importance of making simple details is stressed, in the context of making high-strength composite parts free from wrinkles in the fibers. A case is made that secondary bonding is frequently less expensive than co-curing of complex “single-step” parts, despite the consistent projections that the opposite should be true. Some explanations are presented to explain how this misconception arises, based mainly on the issue that the estimates used for comparison are traditionally based on the costs of making only the first articles, whereas what should have been compared was the cost of making possibly very differently designed lower-cost parts and structures for series production. Some common misunderstandings about variable-thickness adhesives layers are put to rest by explaining how intense load transfer occurs only in small areas, where the adhesive layer is thinnest, with the rest of the bond area inevitably lightly stressed. The problem created by variable thickness bonds is not that of weak bonds. The thicker, and often porous, bond lines usually shed most of the load they were intended to transmit to nearby thin and stiffer areas. Indeed, the loss of load caused by softening can exceed the loss of strength caused by the porosity. No, the problem caused by variable thickness adhesive layers is that it increases the local stresses in the skin whenever the glue layer is thinnest. Traditional problems with release-agent-coated peel plies that prevent adhesion of the glue to the substrate are recounted. This issue is now fairly well known. What is far less understood is the adverse influence of pre-bond moisture that is unable to escape during the bond cycle. This prevents adhesion perhaps even more effectively than a layer of silicone. The importance of bonding only dry parts is explained. This is far easier to do at the time of original manufacture and less easy for in-service repairs and repainting. The paper concludes with a discussion of the important factors to be considered during design and analysis of bonded composite joints.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"32 1","pages":"133-151"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79686441","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":"Strength and Fatigue Life Modeling of Bonded Joints in Composite Structure","authors":"D. Hoyt, S. Ward, Pierre J. A. Minguet","doi":"10.1520/CTR10569J","DOIUrl":"https://doi.org/10.1520/CTR10569J","url":null,"abstract":"The aerospace industry lacks a validated, practical analysis method for the strength, durability, and damage tolerance evaluation of composite bonded joints. This paper presents the results of a combined strength and fracture analysis approach applied to typical bonded joint configurations found in rotorcraft composite structures. The analysis uses detailed 2-D non-linear finite element models of the local bondline. Strength-of-materials failure criteria are used to predict critical damage initiation loads and locations. A fracture mechanics approach is used to predict damage growth and failure under static and cyclic loads based on test data for static fracture toughness (GIc, GIIc) and crack growth rate (da/dN). Results are presented from the application of the analysis approach to two joint configurations: 1) a skin-stiffener T-joint and; 2) a bonded repair lap joint. The results show that the proposed approach can be used to predict critical failure modes, damage initiation loads and locations, crack and/or delamination stability, static strength, residual strength, and fatigue life. Discussion is also included on how this approach can be applied in damage tolerance evaluations of composite bonded joints.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"23 1","pages":"188-208"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73982527","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 LAMINATE DESIGN AND LOADS ON CRACK OPENING VOLUME IN LAMINATES USED IN CRYOGENIC TANKS","authors":"Jae Noh, J. Whitcomb","doi":"10.1520/CTR10957J","DOIUrl":"https://doi.org/10.1520/CTR10957J","url":null,"abstract":"The use of advanced composite materials for cryogenic fuel tanks reduces the mass of the structure but the leakage of fuel can become a problem. Since the amount of leakage will increase with crack opening volume, it is essential that we understand the factors that affect the crack opening. In a previous study by the authors, the degradation behavior of lamina properties due to cracking was studied extensively. The study examined the effects of a variety of parameters such as adjacent ply orientation, material properties of adjacent plies, initial properties of the cracked ply, and cracks in adjacent plies on the effective properties of the cracked ply. It was shown that the rate of degradation is not very sensitive to these parameters. In the current paper, it will be shown that the crack opening volume can be directly related to changes in effective moduli. A simple calculation of the crack opening volume for a laminate based on the degradation of the E22 of a cracked lamina is presented. The effect of various parameters on the crack opening volume shows a similar pattern as the E22 degradation of a cracked ply. This suggests that the opening volume is expected to also be quite insensitive to the laminate design parameters listed above.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"26 1","pages":"11588"},"PeriodicalIF":0.0,"publicationDate":"2002-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76564802","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":"Characterization of Bondline Thickness Effects in Adhesive Joints","authors":"J. Tomblin, P. Harter, W. Seneviratne, C. Yang","doi":"10.1520/CTR10562J","DOIUrl":"https://doi.org/10.1520/CTR10562J","url":null,"abstract":"Growing application of composite materials in airframe structures tends to make significant use of bonded constructions. Despite the large work that has been done on adhesive characterization over previous years, various certification-related issues arise in these applications. The available test methods for determining the in situ properties of an adhesive joint for use in the design must be clarified for thick bondlines, where there is a lack of readily available data. Results from three test methods indicated a decrease in the apparent shear strength as the bondline thickness was increased. The apparent shear strength given by the test methods investigated was found to be highly dependent on the adherend bending stiffness, which directly effects the peel stress distributions in the adhesive layer. In the adhesive strength comparisons as a function of test method, it was found that the thin-adherend tests gave different comparative results than the thick-adherend tests, which were primarily a function of the high peel stresses in the thin-adherend joints. This combined state of stress does not give a true view of the apparent shear stress of the adhesive, but rather an indication of the adhesive behavior under this type of combined loading. It is recommended that thick adherends be used when comparing different adhesive systems for apparent shear strength, and that thin adherends should be used for qualitative tests only.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"93 1","pages":"332-344"},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73865028","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":"The Design of In-Plane Shear and Tension-Loaded Bonded Composite Lap Joints","authors":"Hyonny Kim, K. Kedward","doi":"10.1520/CTR10560J","DOIUrl":"https://doi.org/10.1520/CTR10560J","url":null,"abstract":"The stress analysis of a bonded joint carrying combined in-plane shear and tension load is presented. A general equation is derived that governs the transfer of shear load through a joint. For the case of uniform in-plane shear loading, a closed-form solution exists that is directly analogous to the well-known tension-loaded case. When shear and tension loads are simultaneously applied to a joint, the results of stress analyses treating each loading case separately are superimposed to calculate a combined biaxial shear stress state in the adhesive. Predicting the elastic limit of the adhesive for a lap joint under combined loading is then accomplished by using the von Mises yield criterion. This approach allows the calculation of a limit load envelope that maps the range of combined loading conditions within which the joint is expected to behave elastically. An example design case study of a bonded I-beam shear web is included.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"40 1","pages":"297-307"},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81012280","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":"Stress and Failure Analyses of Adhesive-Bonded Composite Joints Using ASTM D3165 Specimens","authors":"H. Huang, C. Yang, J. Tomblin, P. Harter","doi":"10.1520/CTR10563J","DOIUrl":"https://doi.org/10.1520/CTR10563J","url":null,"abstract":"An analytical model was developed to determine the stress and strain distributions of single-lap adhesive-bonded composite joints under tension. Both the adherend and the adhesive were assumed linear elastic in the derivations. The Laminated Plate Theory was used in defining the mechanical behavior of the composite adherends, whereas the linear elasticity theory was applied to describe the material response of the adhesive. By doing so, the stresses in the adhesive can vary through the bondline thickness. After the overall system of governing equations was determined by energy method, it was solved by using a symbolic solver—Maple with appropriate boundary conditions. Results from the analytical model were verified with finite element analysis using commercial software ABAQUS. Single-lap composite joint experiments were conducted following ASTM D3165, Strength Properties of Adhesives in Shear by Tension Loading of Single-Lap-Joint Laminated Assemblies. Although all three failure modes of bonded joints, substrate, cohesive, and adhesive failure, were present as the experimental results, the substrate failure mode was the major failure mode observed. Therefore, only substrate failure mode was analyzed using the developed model in the present paper. Four failure criteria, Tsai-Hill failure criterion, von Mises failure criterion, maximum interlaminar tensile stress criterion, and maximum normal stress criterion, were used to correlate the stresses and failure load. Nonlinear regression was conducted to determine the necessary parameters in the failure criteria. Based on the experimental results, thicker bondlines result in weaker joints. The variation of failure load for joints with various bondline thicknesses was consistent with the predicted results.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"22 1","pages":"345-356"},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81905387","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":"Surface Preparation Effects on Mode I Testing of Adhesively Bonded Composite Joints","authors":"Jason D. Bardis, K. Kedward","doi":"10.1520/CTR10895J","DOIUrl":"https://doi.org/10.1520/CTR10895J","url":null,"abstract":"The determination and significance of surface preparation on the long-term durability of bonded composite joints is addressed. Several potential factors are evaluated, including the effects of release fabric (sometimes incorrectly referred to as a peel ply) usage and grit blasting on the fracture toughness and failure modes of bonded assemblies. The double cantilever beam (DCB) test is adapted with the intent of developing a quantitative interpretation of a composite version of the wedge test. This well-established wedge test is used for quality and durability assessments of metal bonded systems. In conjunction with conventional lap shear and joint subcomponent testing, this research is directed at enhancing the reliability of composite bonded assemblies that are subjected to long-term loading and varying environmental exposure. DCB tests show that curing nylon release fabrics against adherend surfaces leads to interfacial failures and intermittent crack propagation, with reduced loads and crack opening displacements, giving critical strain energy release rates (G Ic ) lower than bonds produced with equivalent PTFE vacuum bag surfaces. Grit-blasted adherends have higher failure load and G Ic values than nonblasted ones, though the mode of failure does not change.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"210 1","pages":"30-37"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72790032","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":"Comparison of the ±45° Tensile and Iosipescu Shear Tests for Woven Fabric Composite Materials","authors":"M. Kumosa, G. Odegard, D. Armentrout, L. Kumosa, K. Searles, J. Sutter","doi":"10.1520/CTR10892J","DOIUrl":"https://doi.org/10.1520/CTR10892J","url":null,"abstract":"The mechanical response of a woven eight-harness satin graphite/polyimide composite has been investigated by performing ±45° tensile and Iosipescu shear tests at room temperature. Nonlinear finite element simulations of the tests have been conducted to determine internal stress distributions in the ±45° tensile and Iosipescu fabric specimens as a function of load. In the experimental part of this study, a series of tensile and Iosipescu shear tests have been performed. Acoustic emission techniques have been employed to monitor damage initiation and progression in the composite. The finite element computations have shown that the internal stress distributions in the Iosipescu and tensile fabric specimens are significantly different. In the gage sections of Iosipescu specimens, the state of stress is essentially pure shear, whereas the tensile tests generate biaxial stress conditions. It has been shown in this research that the shear strength of the composite determined from the maximum loads obtained from the Iosipescu shear tests is significantly higher than the shear strength obtained from the ±45° tensile tests. Moreover, the initiation of intralaminar damage in the tensile specimens occurs at much lower loads than in the Iosipescu specimens. It appears that the ±45° tensile test significantly underestimates the shear strength of the composite evaluated from the onset of intralaminar damage and the maximum loads.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"1 1","pages":"3-16"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77550859","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":"Temperature Effects on Ultimate Bearing Strength of Polymeric Composite Joints","authors":"W. Counts, W. Johnson","doi":"10.1520/CTR10893J","DOIUrl":"https://doi.org/10.1520/CTR10893J","url":null,"abstract":"The ultimate bearing strength (UBS) of IM7/PETI-5 composite materials in a quasi-isotropic lay-up, 64 plies thick, was determined using a compressive bearing test setup. Testing was performed at room temperature, 177°C (350°F) and −50°C (−58°F). Some specimens were thermally aged at 177°C (350°F) for up to 10000 h. It was found that the IM7/PETI-5 composite material's UBS was essentially unaffected by the thermal aging. At elevated temperature, the UBS of IM7/PETI-5 decreased, while at low temperature, the UBS increased slightly. Despite the increase in UBS at low temperature, the bearing failure was catastrophic, resulting in widespread delamination due to the brittleness of the matrix.","PeriodicalId":15514,"journal":{"name":"Journal of Composites Technology & Research","volume":"25 1","pages":"17-23"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90101850","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}