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The viscoelastic properties of carbon fiber reinforced thermoset composites are of utmost importance during processing such materials using composite forming. The quality of the manufactured parts is largely dependent on intelligent process parameter selection based on the viscoelastic and flow properties of the polymer resin. Viscoelastic properties such as the complex viscosity (η*), storage modulus (G'), loss modulus (G''), and loss tangent (tanδ) are used to determine the critical transition events (such as gelation) during curing. An understanding of the changes in viscoelastic properties as a function of processing temperature and degree of cure provides insight to establish a suitable processing range for compression forming of prepreg systems. However, tracking viscoelastic properties as a function of cure during the forming process is a challenging task. In this current work, we have investigated the effect of sample size and adhesive type on the rheological properties of a commercially available carbon fiber prepreg material. Specifically, determining the linear viscoelastic region (LVE) as a function of sample configuration and different adhesive chemistries were explored. The results suggest that the square-shaped sample geometries coupled with cyanoacrylate based adhesive are optimum for conducting rheological characterization on the carbon fiber prepreg system.
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Viscosity Effects on Reaction Induced Phase Separation and Resulting Morphologies of Thermoplastic Toughened Epoxy Networks
This research investigates how reaction induced phase separation (RIPS) of thermoplastic, which occurs during glassy polymer network cure, is determined by viscosity. Utilizing high Tg engineering thermoplastics in high viscosity thermoset systems, dissolution of multiple loading levels of thermoplastic and thermoset pre-polymer conversion will be achieved through use of a high shear continuous reactor. Samples will be cured using various isothermal curing profiles and characterized for morphology type and domain size as well as rheologically to determine minimum viscosity, time to gelation, time from phase separation to gelation, and average viscosity. The influence of cure conditions, thermoplastic loading levels, thermoplastic composition, and molecular weight on structural morphology will be resolved, establishing a well-defined rheological well during cure that leads to tunable and controllable phase separated morphologies, from dispersed droplet to co-continuous. By controlling viscosity of thermoplastic dispersed network pre-polymers through phase composition, cure schedule, molecular weight, directed phase separation will be achieved. Rheological profiles will be related to resulting network structure, which will lead to the ability to control and direct complex thermoplastic filled thermoset systems to targeted unique morphologies.
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- Award ID(s):
- 1659340
- PAR ID:
- 10054413
- Date Published:
- Journal Name:
- CAMX: The Composites and Advanced Materials Expo
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
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- The DOI is not currently available.
