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Polymers 2018, 10(2), 125; https://doi.org/10.3390/polym10020125

Effect of Curing Rate on the Microstructure and Macroscopic Properties of Epoxy Fiberglass Composites

1
Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
2
Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, VA 23529, USA
*
Author to whom correspondence should be addressed.
Received: 11 December 2017 / Revised: 21 January 2018 / Accepted: 24 January 2018 / Published: 27 January 2018
(This article belongs to the Special Issue Processing-Structure-Properties Relationships in Polymers)
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Abstract

Curing rates of an epoxy amine system were varied via different curing cycles, and glass-fiber epoxy composites were prepared using the same protocol, with the aim of investigating the correlation between microstructure and composite properties. It was found that the fast curing cycle resulted in a non-homogenous network, with a larger percentage of a softer phase. Homogenized composite properties, namely storage modulus and quasi-static intra-laminar shear strength, remained unaffected by the change in resin microstructure. However, fatigue tests revealed a significant reduction in fatigue life for composites cured at fast curing rates, while composites with curing cycles that allowed a pre-cure until the critical gel point, were unaffected by the rate of reaction. This result was explained by the increased role of epoxy microstructure on damage initiation and propagation in the matrix during fatigue life. Therefore, local non-homogeneities in the epoxy matrix, corresponding to regions with variable crosslink density, can play a significant role in limiting the fatigue life of composites and must be considered in the manufacturing of large scale components, where temperature gradients and significant exotherms are expected. View Full-Text
Keywords: curing rate; epoxy microstructure; fatigue; composites; critical gel curing rate; epoxy microstructure; fatigue; composites; critical gel
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Patel, A.; Kravchenko, O.; Manas-Zloczower, I. Effect of Curing Rate on the Microstructure and Macroscopic Properties of Epoxy Fiberglass Composites. Polymers 2018, 10, 125.

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