Effect of internal moisture content and dynamic mechanical analysis testing conditions on the Tg values of CFRP tendons

Eleni Toumpanaki; Janet M  Lees; Michel Barbezat; Giovanni Terrasi

doi:10.1016/j.conbuildmat.2019.116771

Effect of internal moisture content and dynamic mechanical analysis testing conditions on the Tg values of CFRP tendons

Eleni Toumpanaki, Janet M Lees, Michel Barbezat, Giovanni Terrasi

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Abstract

The high temperature and long-term performance of uni-directional pultruded carbon fibre reinforced polymer (CFRP) tendons in prestressed concrete relies on the integrity of the epoxy matrix and the degree of crosslinking. The dynamic glass transition temperature (Tg) obtained using Dynamic Mechanical Analysis (DMA) can be a useful indicator of the degree of cross-linking. However, variations in the epoxy plasticisation due to different initial hygrothermal equilibrium conditions in CFRP tendons can influence the measured Tg leading to inconsistent results. The dependency of Tg on the initial CFRP moisture content, and also DMA test parameters including the thermocouple position, the magnitude of static flexural strain, the static to dynamic strain ratio and the specimen geometry were investigated. Whereas the selected DMA test parameters had only a small influence on the Tg values, the initial moisture content of the CFRP tendon had a significant effect. A decrease in Tg of up to 38C was observed with an increase in average moisture content of up to 2.46%. Knowledge of the initial moisture content and the establishment of a comparative baseline are necessary to more accurately infer the crosslinking density and degree of cure of a resin from dynamic Tg results.

Original language	English
Article number	116771
Number of pages	14
Journal	Construction and Building Materials
Volume	227
Early online date	7 Sept 2019
DOIs	https://doi.org/10.1016/j.conbuildmat.2019.116771
Publication status	Published - 10 Dec 2019

Keywords

CFRP
DMA test
Material characterisation
Environmental conditions

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This is the author accepted manuscript (AAM). The final published version (version of record) is available online via Elsevier at https://www.sciencedirect.com/science/article/pii/S0950061819321890. Please refer to any applicable terms of use of the publisher.
Accepted author manuscript, 1.96 MBLicence: CC BY-NC-ND

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Dr Eleni Toumpanaki
- eleni.toumpanakibristol.acuk
- School of Civil, Aerospace and Design Engineering - Senior Lecturer
- Cabot Institute for the Environment
- Bristol Composites Institute
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title = "Effect of internal moisture content and dynamic mechanical analysis testing conditions on the Tg values of CFRP tendons",

abstract = "The high temperature and long-term performance of uni-directional pultruded carbon fibre reinforced polymer (CFRP) tendons in prestressed concrete relies on the integrity of the epoxy matrix and the degree of crosslinking. The dynamic glass transition temperature (Tg) obtained using Dynamic Mechanical Analysis (DMA) can be a useful indicator of the degree of cross-linking. However, variations in the epoxy plasticisation due to different initial hygrothermal equilibrium conditions in CFRP tendons can influence the measured Tg leading to inconsistent results. The dependency of Tg on the initial CFRP moisture content, and also DMA test parameters including the thermocouple position, the magnitude of static flexural strain, the static to dynamic strain ratio and the specimen geometry were investigated. Whereas the selected DMA test parameters had only a small influence on the Tg values, the initial moisture content of the CFRP tendon had a significant effect. A decrease in Tg of up to 38C was observed with an increase in average moisture content of up to 2.46%. Knowledge of the initial moisture content and the establishment of a comparative baseline are necessary to more accurately infer the crosslinking density and degree of cure of a resin from dynamic Tg results.",

keywords = "CFRP, DMA test, Material characterisation, Environmental conditions",

author = "Eleni Toumpanaki and Lees, {Janet M} and Michel Barbezat and Giovanni Terrasi",

year = "2019",

month = dec,

day = "10",

doi = "10.1016/j.conbuildmat.2019.116771",

language = "English",

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journal = "Construction and Building Materials",

issn = "0950-0618",

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TY - JOUR

T1 - Effect of internal moisture content and dynamic mechanical analysis testing conditions on the Tg values of CFRP tendons

AU - Toumpanaki, Eleni

AU - Lees, Janet M

AU - Barbezat, Michel

AU - Terrasi, Giovanni

PY - 2019/12/10

Y1 - 2019/12/10

N2 - The high temperature and long-term performance of uni-directional pultruded carbon fibre reinforced polymer (CFRP) tendons in prestressed concrete relies on the integrity of the epoxy matrix and the degree of crosslinking. The dynamic glass transition temperature (Tg) obtained using Dynamic Mechanical Analysis (DMA) can be a useful indicator of the degree of cross-linking. However, variations in the epoxy plasticisation due to different initial hygrothermal equilibrium conditions in CFRP tendons can influence the measured Tg leading to inconsistent results. The dependency of Tg on the initial CFRP moisture content, and also DMA test parameters including the thermocouple position, the magnitude of static flexural strain, the static to dynamic strain ratio and the specimen geometry were investigated. Whereas the selected DMA test parameters had only a small influence on the Tg values, the initial moisture content of the CFRP tendon had a significant effect. A decrease in Tg of up to 38C was observed with an increase in average moisture content of up to 2.46%. Knowledge of the initial moisture content and the establishment of a comparative baseline are necessary to more accurately infer the crosslinking density and degree of cure of a resin from dynamic Tg results.

AB - The high temperature and long-term performance of uni-directional pultruded carbon fibre reinforced polymer (CFRP) tendons in prestressed concrete relies on the integrity of the epoxy matrix and the degree of crosslinking. The dynamic glass transition temperature (Tg) obtained using Dynamic Mechanical Analysis (DMA) can be a useful indicator of the degree of cross-linking. However, variations in the epoxy plasticisation due to different initial hygrothermal equilibrium conditions in CFRP tendons can influence the measured Tg leading to inconsistent results. The dependency of Tg on the initial CFRP moisture content, and also DMA test parameters including the thermocouple position, the magnitude of static flexural strain, the static to dynamic strain ratio and the specimen geometry were investigated. Whereas the selected DMA test parameters had only a small influence on the Tg values, the initial moisture content of the CFRP tendon had a significant effect. A decrease in Tg of up to 38C was observed with an increase in average moisture content of up to 2.46%. Knowledge of the initial moisture content and the establishment of a comparative baseline are necessary to more accurately infer the crosslinking density and degree of cure of a resin from dynamic Tg results.

KW - CFRP

KW - DMA test

KW - Material characterisation

KW - Environmental conditions

U2 - 10.1016/j.conbuildmat.2019.116771

DO - 10.1016/j.conbuildmat.2019.116771

M3 - Article (Academic Journal)

SN - 0950-0618

VL - 227

JO - Construction and Building Materials

JF - Construction and Building Materials

M1 - 116771

ER -

Effect of internal moisture content and dynamic mechanical analysis testing conditions on the Tg values of CFRP tendons

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