Research Outputs

Permanent URI for this communityhttps://hdl.handle.net/20.500.14288/2

Browse

Filters

2013 - 20173

Advanced Search

Filter by

Settings

Quartile: search.filters.quartile.Q3Subject: search.filters.subject.Composite materials

Search Results

Now showing 1 - 3 of 3
  • Placeholder
    PublicationMetadata only
    Compaction of e-glass fabric preforms in the vacuum infusion process: (a) use of characterization database in a model and (b) experiments
    (Sage Publications Ltd, 2013) N/A; Department of Mechanical Engineering; Yenilmez, Bekir; Sözer, Murat; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 110357
    Compaction of e-glass fabric preforms (random, woven and biaxial) embedded with a distribution medium (polypropylene) is coupled with 1D resin (polyester) flow during initial application of vacuum, mold filling and fiber relaxation stages of vacuum infusion. In our previous study,(1) the compaction characterization procedure had been designed and conducted to realistically model the compaction behavior of fiber preforms in vacuum infusion such that the loading was done on a dry specimen; fiber settling was allowed under constant compaction pressure; unloading was done after the specimen was wetted and the fiber relaxation was characterized at constant pressure. To investigate the effects of characterization components on the part thickness evolution, two compaction models (unloading only and unloading and time-dependent relaxation) were coupled with two models of flow (uncoupled and coupled pressure-thickness-permeability). The results of the coupled model of unloading and time-dependent relaxation and coupled pressure-thickness-permeability was the closest to the vacuum infusion experiments.
  • Placeholder
    PublicationMetadata only
    Pressure-controlled compaction characterization of fiber preforms suitable for viscoelastic modeling in the vacuum infusion process
    (Sage Publications Ltd, 2017) N/A; N/A; Department of Mechanical Engineering; Yenilmez, Bekir; Çağlar, Barış; Sözer, Murat; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 110357
    A woven fabric's compaction in the vacuum infusion process is characterized by applying an initial settling under a minor load, compaction, settling under a major load, decompaction and relaxation. The effects of compaction rate, relaxation pressure, wetting and debulking cycles are all investigated. Although wetting helps by increasing fiber volume fraction insignificantly, its contribution is more significant during debulking cycles by increasing the fiber volume fraction to 57.4% as compared to 55.4% for the debulked dry specimens. Recovery during decompaction is much less than the deformation during compaction, and thinning/thickening of the specimens with time under constant pressure, so called settling/relaxation pressures, indicates that fabric specimens are not elastic materials, but viscoelastic. The experimental data of this study will be valuable to compare different viscoelastic and elastic compaction models in our next study.
  • Placeholder
    PublicationMetadata only
    Viscoelastic modeling of fiber preform compaction in vacuum infusion process
    (Sage, 2017) Department of Mechanical Engineering; Department of Mechanical Engineering; Department of Mechanical Engineering; Yenilmez, Bekir; Çağlar, Barış; Sözer, Murat; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; 110357
    A woven fabric's compaction was modeled by using five viscoelastic models - Maxwell, Kelvin-Voigt, Zener, Burgers, and Generalized Maxwell - to reveal the capabilities and limitations of the models. The model parameters were optimized by minimizing the deviation between the model results and experimental data collected in our previous material characterization study mimicking different compaction stages (loading, fiber settling, wetting, unloading, and fiber relaxation) that a fiber structure undergoes during vacuum infusion process. Although Burgers and Generalized Maxwell models have the highest performance due to their almost equal coefficient of determination values, they have diverse characteristics in terms of modeling different stages of compaction. Burgers model allowed modeling the permanent deformation in relaxation stage, but failed in modeling permanent deformation in settling stage. Generalized Maxwell model could do the opposite, i.e. failed in the former and could handle the latter. This study's major contribution is a holistic numerical approach and its conclusions by modeling all stages of the vacuum infusion process instead of one stage at a time, and thus optimizing only one set of model parameters (constants of springs and dampers) since they do not change with time. The numerical results of different models were fit to the results of a specially designed compaction characterization experiments conducted in our complementary study.