Calorimetric and Rheological Measurements of Three Commercial Thermosetting                 Prepreg Epoxies

Hargis, Mitch; Grady, Brian P.; Aktas, Levent; Bomireddy, Krishnasumanth R.; Howsman, Steve; Altan, M. Cengiz; Rose, T. L.; Rose, H.

doi:10.1177/0021998305056380

Cited by 17 publications

(15 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The viscosity of the silicone (100 and 60,000 cSt for shear and torsion strain, respectively) was important to optimize avoiding dripping. The phenolic resin studied, in these conditions, reacts similarly to a polyester resin studied by DMA and DSC techniques 44…”

Section: Resultsmentioning

confidence: 99%

Isothermal rheokinetic study of a precured resol resin beyond gelation by torsion

Domínguez

Oliet

Alonso

et al. 2011

J of Applied Polymer Sci

View full text Add to dashboard Cite

The rheokinetics of the curing process of a resol resin was studied through isothermal analysis. The resin was subjected to a curing pretreatment until gelation was reached. Rectangular torsion was chosen as the appropriate strain form to carry out the study of the resin's curing kinetics, because the viscoelastic behavior of the material was closer to an ideal solid than to a Newtonian fluid. Seven operating temperatures were selected for analysis (80-110 C). The Arrhenius and Kiuna rheokinetic models were applied to the resin's complex viscosity (g*) evolution during the crosslinking of polymer. The resol resin had curing activation energies of 62.6 and 65.8 kJ/ mol when the Arrhenius model was applied in four-and six-parameter forms, respectively. The Kiuna model was proposed to fit the nonlinear viscosity region found at the highest temperatures. This model was suitable to predict changes in the resin's complex viscosity, obtaining a curing activation energy of 69.5 kJ/mol for the resin. In addition, the evolution of the degree of mechanical curing was obtained from the elastic modulus, rather than from the more common DSC technique.

show abstract

Section: Resultsmentioning

confidence: 99%

Isothermal rheokinetic study of a precured resol resin beyond gelation by torsion

Domínguez

Oliet

Alonso

et al. 2011

J of Applied Polymer Sci

View full text Add to dashboard Cite

show abstract

“…In addition to thermal aging, Equation (1), in this generic form, has been used to develop phenomenological models for various other applications, including cure modeling of thermoset resins and composite prepregs, and also for describing microstructural changes [18][19][20][21][22].…”

Section: K(t)g(φ)mentioning

confidence: 99%

Thermo-oxidative degradation of graphite/epoxy composite laminates: Modeling and long-term predictions

Ozcelik¹,

Aktas²,

Altan

2009

Express Polym. Lett.

View full text Add to dashboard Cite

Abstract. Thermo-oxidative degradation of graphite/epoxy composite laminates due to exposure to elevated temperatures was characterized using weight loss and short beam strength (SBS) reduction data. Test specimens obtained from 24-ply, unidirectional AS4/3501-6 graphite/epoxy laminates were subjected to 100, 150, 175, and 200°C for 5000 hours (208 days) in air. Predictive differential models for the weight loss and short beam strength reduction were developed using the isothermal degradation data only up to 2000 hours. Then, the predictive capabilities of both models were demonstrated using the longer term, 5000 hours degradation data. The proposed models were first order differential expressions that can be used to predict degradation in an arbitrary, time-dependent temperature environment. Both models were able to estimate the actual degradation levels accurately. In particular, excellent agreement was obtained when the degradation temperature was lower than 200°C.

show abstract

“…This is mainly because the curing mechanism of thermosetting composite materials is more complicated than that of thermosetting resins. For example, the moisture absorption, fiber sizing, and initial degree of conversion (α 0 ) affect the curing behavior and postcuring properties of prepregs 1–3. Moreover, the flowability of resin in the prepreg significantly affects the rate of crosslinking reactions during curing.…”

Section: Introductionmentioning

confidence: 99%

“…In the first method, one calculates α by dividing H ( t ) by a constant H U , which is assumed to be a material property:1, 3–5, 8, 19, 20 where dH ( t )/ dt is the rate of heat generation (heat flow) and H U, dyn is the ultimate heat of reaction obtained from dynamic scanning. Equation (1) has commonly been used to obtain α as a continuous function of the curing time.…”

Section: Introductionmentioning

confidence: 99%

“…As such, α of prepregs should be modified with eq. (5) to account for α 0 :3, 16 where α is the degree of conversion obtained from DSC on the basis of eq. (1) or (2), α 0 is the initial degree of conversion of a prepreg, and α m is the modified degree of conversion changes significantly in the early stages of curing where α is far below unity.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

New method for estimating the extent of curing of thermosetting prepregs

Sabzevari

Alavi-Soltani

Minaie

2011

J of Applied Polymer Sci

View full text Add to dashboard Cite

Here, we propose a new method for estimating the extent of curing of thermosetting prepregs. In the proposed method, the extent of curing is estimated with the curing index (C i ), defined as the ratio of the glasstransition temperature (T g ) to the ultimate glass-transition temperature of the material. The advantages of this new method over the conventional degree of conversion (a) for estimating the extent of curing of thermosetting prepregs are discussed in detail. C i and a of a toughened epoxy prepreg (977-2 unidirectional) were obtained for a wide range of isothermal curing temperatures with a differential scanning calorimeter. The ultimate heat of reaction varied inconsistently with decreasing curing temperature; this resulted in erratic behavior of a. However, C i provided a more consistent estimate of the extent of curing because T g , unlike a, did not need to be modified on the basis of the curing history of the material and was measured directly with the heat-flow data from differential scanning calorimetry. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: [883][884][885][886][887][888][889][890][891] 2011

show abstract

Calorimetric and Rheological Measurements of Three Commercial Thermosetting Prepreg Epoxies

Cited by 17 publications

References 17 publications

Isothermal rheokinetic study of a precured resol resin beyond gelation by torsion

Isothermal rheokinetic study of a precured resol resin beyond gelation by torsion

Thermo-oxidative degradation of graphite/epoxy composite laminates: Modeling and long-term predictions

New method for estimating the extent of curing of thermosetting prepregs

Contact Info

Product

Resources

About