Characterization and modeling of stiffness reduction in SCS-6-Ti composites under low cycle fatigue loading

Wang, P.C.; Jeng, S. M.; Yang, Jenn‐Ming

doi:10.1016/0921-5093(95)07011-7

Cited by 19 publications

(4 citation statements)

References 11 publications

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“…Polymerizations carried out in the absence of initiator (Table ) confirmed that considerable direct initiation is operational during the polymerization, and the presence of initiator, p -MeStCl, makes very little difference. It has already been reported that in polar solvents in the presence of proton trap BCl 3 alone can initiates the polymerization of St . Therefore, it was concluded that the cationic polymerization of p -MeSt with the p -MeStCl/BCl 3 initiating system in CH 2 Cl 2 is mainly due to direct initiation.…”

Section: Resultsmentioning

confidence: 94%

Determination of the Absolute Rate Constant of Propagation for Ion Pairs in the Cationic Polymerization of p-Methylstyrene

Faust

2005

Macromolecules

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The cationic polymerization of p-methylstyrene (p-MeSt) was studied in dichloromethane, chloroform, and methylcyclohexane/methyl chloride 60/40 (v/v) at different temperatures with various initiators in conjunction with different Lewis acids, TiCl 4, BCl3, SnBr4, and SnCl4. Well-controlled living cationic polymerization was obtained in dichloromethane, in conjunction with SnCl4 as Lewis acid, and the living nature of the polymerization was verified by linear first-order ln([M]0/[M]) vs time and linear number-average molecular weight (Mn) vs conversion plots in the temperature range of -15 to -70 °C. The number-average molecular weight of the polymers increased in direct proportion to monomer conversion up to M n ≈ 90 000 and agreed reasonably well with the calculated molecular weight, assuming that one polymer chain forms per molecule of initiator. The kinetics of p-MeSt polymerization suggests that the polymerization is first order with respect to SnCl4 concentration. Employing the model compound 1-chloro-1-(4-methylphenyl)ethane in conjunction with SnCl4 in CH2Cl2, UV-vis spectroscopy was used to follow the capping reaction with 2-phenylfuran to determine the equilibrium constant of ionization (K i) at -30 °C. From the Ki value and the apparent rate constant of propagation (kapp) the absolute rate constant of propagation for ion pairs, kp ( ) 6.8 × 10 8 L mol -1 s -1 at -30 °C, was calculated as a lower limit. The absolute rate constant of propagation for ion pairs, kp ( , was also determined at different temperatures from competition experiments, where polymerizations were carried out in the presence of 2-phenylfuran as capping agent. Gel permeation chromatography and NMR spectroscopy suggested complete capping of the polymeric cation and the absence of side reactions. From the limiting conversion and limiting number-average degrees of polymerization k p ( ) 1 × 10 9 L mol -1 s -1 was calculated using the known rate constant of capping. The kp ( value remained unaffected in the temperature range of -15 to -70 °C, indicating that propagation does not have an enthalpic barrier.

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Section: Resultsmentioning

confidence: 94%

Determination of the Absolute Rate Constant of Propagation for Ion Pairs in the Cationic Polymerization of p-Methylstyrene

Faust

2005

Macromolecules

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“…Recently we reported that boron halides (BX 3 ) alone can initiate the living polymerization of isobutylene (IB) and styrene (St) in polar solvents in the presence of a proton trap (2,6-di- tert -butylpyridine; DTBP) to prevent initiation by protic impurities. On the basis of kinetic and mechanistic studies with IB, the initiation mechanism was found to be haloboration (Scheme b) …”

Section: Introductionmentioning

confidence: 99%

“…The products are low molecular weight asymmetric telechelic polymers, carrying X 2 B− head groups and halo end groups. The head groups were quantitatively converted to other functionalities, most notably to primary alcohols upon oxidation by alkaline hydrogen peroxide in tetrahydrofuran at room temperature …”

Section: Introductionmentioning

confidence: 99%

Initiation via Haloboration in Living Cationic Polymerization. 4. The Polymerization of α-Methylstyrene

1997

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The polymerization of R-methylstyrene was studied in the absence of a separately added cationogen (i.e., initiator) and in the presence of a proton trap, using boron halides (BX3, X ) Cl, Br, and I). The effect of the monomer and BX3 concentration, solvent polarity, and temperature was examined. The polymerization rates increased with decreasing temperature and with increasing solvent polarity. The molecular weight (Mn) of the products also increased with decreasing temperature; however it was relatively independent of solvent polarity. Under identical conditions the Mn's were highest with BCl3, lower with BBr3, and lowest with BI3. Kinetic experiments support that initiation is by haloboration, but direct proof was only obtained for BI3. For polymers made with BI3 the presence of one boron per chain was confirmed by elemental analysis, while the high Mn's obtained with BCl3 and BBr3 prevented quantitative analysis of head and end groups.

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“…The beam is assumed to be a time‐variant mechanical system subjected to gradual stiffness degradation at particular element locations that is simulated by introducing elastic modulus reduction. It is commonly accepted that for the vast majority of the structures, stiffness decay because of damage evolution process can be modelled by a scheme shown in Figure (a) . As exhibited, in the initial stages, deterioration occurs in an approximately linear and slight fashion followed by abrupt and rapid reduction in the stiffness that consequently results in failure.…”

Section: Applicationmentioning

confidence: 99%

Damage localization based on symbolic time series analysis

Alamdari

Samali

2014

Struct. Control Health Monit.

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Summary The objective of this paper is to localize damage in a single or multiple state at early stages of development on the basis of the principles of symbolic dynamics. Symbolic time series analysis (STSA) of noise‐contaminated responses is used for feature extraction to detect and localize a gradually evolving deterioration in the structure according to the changes in the statistical behaviour of symbol sequences. Basically, in STSA, statistical features of the symbol sequence can be used to describe the dynamic status of the system. Symbolic dynamics has some useful characteristics making it highly demanded for implementation in real‐time observation application such as SHM. First, it significantly reduces the dimension of information and provides information‐rich representation of the underlying data. Second, symbolic dynamics and the set of statistical measures built upon it represent a solid framework to address the main challenges of the analysis of nonstationary time data. Finally, STSA often allows capturing the main features of the underlying system whilst alleviating the effects of harmful noise. The method presented in this paper consists of four primary steps: (i) acquisition of the time series data; (ii) creating the symbol space to produce symbol sequences on the basis of the wavelet transformed version of time series data; (iii) developing the symbol probability vectors to achieve anomaly measures; and (iv) localizing damage on the basis of any sudden variation in anomaly measure of different locations. The method was applied on a flexural beam and a 2‐D planar truss bridge subjected to varying Gaussian excitation in presence of 2% white noise to examine the efficiency and limitations of the method. Simulation results under various damage conditions confirmed the efficiency of the proposed approach for localization of gradually evolving deterioration in the structure; however, for the future work, the method needs to be verified by experimental data. Copyright © 2014 John Wiley & Sons, Ltd.

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Characterization and modeling of stiffness reduction in SCS-6-Ti composites under low cycle fatigue loading

Cited by 19 publications

References 11 publications

Determination of the Absolute Rate Constant of Propagation for Ion Pairs in the Cationic Polymerization of p-Methylstyrene

Determination of the Absolute Rate Constant of Propagation for Ion Pairs in the Cationic Polymerization of p-Methylstyrene

Initiation via Haloboration in Living Cationic Polymerization. 4. The Polymerization of α-Methylstyrene

Damage localization based on symbolic time series analysis

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