Experimental investigation of the cure‐dependent response of vinyl ester resin

Flores, F.; Gillespie, John W.; Bogetti, Travis A.

doi:10.1002/pen.10973

Cited by 12 publications

(7 citation statements)

References 7 publications

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“…On vitrification the system, either a rubbery network or a viscous liquid (if vitrification precedes gelation), is transformed into a glassy state. The property change was shown to be closely related to the degree of cure of the resin (Stone et al, 2000;Flores et al, 2002). Here, the properties of the resin were assumed to be independent of the degree of cure and constant at the isothermal curing temperature.…”

Section: Methodsmentioning

confidence: 99%

A micromechanical study of residual stress and its effect on transverse failure in polymer–matrix composites

Warrior

Long

2006

International Journal of Solids and Structures

118

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Cure residual stress and its effect on damage in unidirectional fibre-reinforced polymer-matrix composites under transverse loading were studied using a micromechanical unit cell model and the finite element method. The overall residual stress introduced from curing was determined by considering two contributions: volume shrinkage of matrix resin from the crosslink polymerization during isothermal curing and thermal contraction of both resin and fibre as a result of cooling from the curing temperature to room temperature. To examine the effect of residual stress on failure, a model based on the Maximum Principal Stress criterion and stiffness degradation technique was used for damage analysis of the unit cell subjected to mechanical loading after curing. Predicted damage initiation and evolution are clearly influenced by the inclusion of residual stress. Residual stress is always detrimental for transverse compressive loading and pure shear loading. For transverse tensile loading, residual stress is detrimental for relatively low resin strength and beneficial for relatively high resin strength. Failure envelopes were obtained for both biaxial normal loading and combined shear and normal loading and the results show that residual stress results in a shifting and contraction of the failure envelopes.

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Section: Methodsmentioning

confidence: 99%

A micromechanical study of residual stress and its effect on transverse failure in polymer–matrix composites

Warrior

Long

2006

International Journal of Solids and Structures

118

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“…Gillespie and co-workers [49,50] measured in situ the Sh of vinylester resin using a density gradient column [24] technique. A plaque of resin was cast under the desired isothermal condition (30°C).…”

Section: From Density Variationmentioning

confidence: 99%

Chemical shrinkage characterization techniques for thermoset resins and associated composites

et al. 2013

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International audienceControl and optimization of curing process is very important for the production of high quality composite parts. Crosslinking of molecules of thermoset resin occurs in this phase, which involves exothermy of reaction, chemical shrinkage (Sh) and development of thermo-physical and thermo-mechanical properties. Exact knowledge of the evolution of all these parameters is required for the better understanding and improvement of the fabrication process. Sh is one such property of thermoset matrix, which is difficult to characterize due to its coupling with thermal expansion/contraction. A number of techniques have been used to determine volume Sh of thermoset matrix, which later on has been used to find tensor of Sh for the simulation of residual stresses and shape distortion of composite part, etc. Direct characterization of volume Sh of composites has also been made by some authors. Though not much, but some work has also been reported to determine the Sh of composite part in a specific direction. In this article, all the techniques used in the literature for the characterization of Sh of resin and composite are reported briefly with their respective advantages, disadvantage and important results

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“…2. The measured shrinkage evolution was fitted nicely by the general kinetic equation for epoxies [4]. Bragg Wavelength (nm) Time (min) 1549.112nm ( 175 o C ) Fig.1 Bragg wavelength shift of Configuration I during polymerization.…”

mentioning

confidence: 78%

“…2. The measured shrinkage evolution was fitted nicely by the general kinetic equation for epoxies [4]. In the configuration II, the radius of the polymer cured around the FBG was 20 times larger than the radius of the fiber, i.e., 1.25 mm.…”

mentioning

confidence: 84%

Characterization of effective chemical shrinkage and modulus evolution during polymerization

Yong

Han

2007

2007 12th International Symposium on Advanced Packaging Materials: Processes, Properties, and Interfaces

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Mechanical and thermal characterization of polymeric materials is critical to "predictive modeling" required for reliability assessment and design optimization at the conceptual stage of a new product development. One of the most critical polymeric properties required for predictive stress modeling is "chemical shrinkage" developed during the polymerization process. Residual stresses induced by the chemical shrinkage can largely influence the performance and reliability of packages [1].The issue of "chemical shrinkage" is not new. Numerous testing methods have been developed for many decades and some of them are practiced routinely to measure the intrinsic (or total) chemical shrinkage of polymers. It is important to note, however, that not all of the intrinsic chemical shrinkage contributes to the residual stresses simply because some of chemical shrinkage occurs before the gelation point where polymers start to build mechanical strength [2].This study proposes an innovative measurement method to measure the effective chemical shrinkage. The method is based on a fiber Bragg grating (FBG) sensor. A polymer of interest is cured around a glass FBG and the Bragg wavelength shift is continuously measured and documented while polymerization progresses at the curing temperature. This configuration is referred to as Configuration I [3]. From the theoretical relationship between the Bragg wavelength shift and the effective chemical shrinkage, the evolution of the effective chemical shrinkage is determined by the measured Bragg wavelength shift.Another important property that is required for accurate determination of the residual stresses is Young's modulus, which changes non-linearly during the shrinkage evolution. Without the information about the modulus evolution, the residual stress produced by the chemical shrinkage cannot be determined accurately. A physical configuration different from one that was used for chemical shrinkage is utilized to determine the modulus evolution (this configuration is referred to as Configuration II). In this configuration, Bragg wavelength changes with both effective chemical shrinkage and modulus. The modulus evolution is then determined from the measured Bragg wavelength shift using the effective chemical shrinkage that has been determined previously from Configuration I.The proposed method was implemented for an underfill material. In the configuration I, the radius of the polymer cured around the FBG was 200 times larger than the radius of the fiber, i.e., 12.5 mm. The experimentally measured Bragg wavelength evolution during the curing process is shown in Fig.1. The effective chemical shrinkage determined from the data is shown in Fig. 2. The measured shrinkage evolution was fitted nicely by the general kinetic equation for epoxies [4]. Bragg Wavelength (nm) Time (min) 1549.112nm ( 175 o C ) Fig.1 Bragg wavelength shift of Configuration I during polymerization. 0 4 0 8 0 1 2 0 1 6 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Chemical shrinkage (%) Time (min) Measured Predicted Fig.2 Evolution of ...

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Experimental investigation of the cure‐dependent response of vinyl ester resin

Cited by 12 publications

References 7 publications

A micromechanical study of residual stress and its effect on transverse failure in polymer–matrix composites

A micromechanical study of residual stress and its effect on transverse failure in polymer–matrix composites

Chemical shrinkage characterization techniques for thermoset resins and associated composites

Characterization of effective chemical shrinkage and modulus evolution during polymerization

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