Experimental investigation of morphological and thermomechanical properties of frontally cured carbon fibre reinforced epoxy composites

Valerie Grasser

Research output: ThesisMaster's Thesis

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Abstract

Lightweight coupled with high mechanical strength are the most important parameters of fibre reinforced thermosets in order to comply with the concept of sustainable mobility. However, the curing processes of those materials are usually linked with high temperatures and pressures, as well as prolonged cycle times. Therefore their manufacturing is costly and time-consuming. A possibility of reducing manufacturing costs of fibre reinforced composites is by following curing of composites via frontal polymerization. In this curing technique, the reaction is initiated by an external trigger (e. g. UV-radiation or heat), that releases high amount of energy in the course of the curing process, generating a self-sustaining reaction front and consequently curing the resin without further input of an external trigger. In the course of this master’s thesis, carbon fibre reinforced epoxy composites, with a fibre volume content of at least 50%, were cured via thermally initiated frontal polymerization. Subsequently, the thermomechanical properties were determined, in comparison to the corresponding conventionally cured composites. A unidirectional (UD) 50 k lamina and a 2×2 twill fabric were used as reinforcement material along with
two commercially available bisphenol A based derivates as matrix materials. These composites based on UD and carbon fibre fabric were manufactured via a wet layup (wlu) and a vacuum assisted resin infusion (VARI) process.
From the results of dynamic mechanical analysis (DMA), approximately 20 °C higher glass transistion temperature (Tg) values were determined for the frontally cured specimens than the conventional anhydride/amine cured specimens. Tensile test results from frontally cured specimens of both fibre types showed comparable modulus values, yet lower maximum strength and strain values than the corresponding conventional cured specimens. The difference in tensile strength, comparing specimens with same
manufacturing process, reinforcement and resin material, yet different curing method showed high deviations. The compression properties of the frontally cured specimens were comparable to one conventionally cured resin type and higher than the other resin material used. The analysis of the inter laminar shear strength (ILSS) on the one hand showed different failure modes for frontally (shear failure) and conventionally (plastic deformation) cured specimens. Yet on the other hand, the strength values at which the failure appeared show no distinct trends to higher values for neither curing nor resin type.
Translated title of the contributionMorphologie und thermomechanische Eigenschaften von mittels frontaler Polymerisation gehärteten Epoxidharz Kohlenstofffaser Verbundwerkstoffen
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Pinter, Gerald, Supervisor (internal)
Award date22 Oct 2021
Publication statusPublished - 2021

Bibliographical note

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Keywords

  • composite
  • fast curing
  • thermomechanical properties

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