TY - JOUR
T1 - Uncovering the fatigue damage initiation and progression in uni-directional non-crimp fabric reinforced polyester composite
AU - Jespersen, Kristine M.
AU - Glud, Jens A.
AU - Zangenberg, Jens
AU - Hosoi, Atsushi
AU - Kawada, Hiroyuki
AU - Mikkelsen, Lars P.
N1 - Funding Information:
Financial support from CINEMA: “ the allianCe for ImagiNg of Energy MAterials ”, DSF-Grant No. 1305-00032B under “The Danish Council for Strategic Research” is gratefully acknowledged. This research was conducted using mechanical testing equipment from DTU Center for Advanced Structural and Material Testing (CASMAT), Grant No. VKR023193 from Villum Fonden. Additionally we would like to thank LM Wind Power for manufacturing of test specimens. Finally, we would like to thank Steffen Rasmussen and Anthony Fraisse from DTU Wind Energy for their assistance with mechanical tests.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/6
Y1 - 2018/6
N2 - The current work studies the fatigue damage initiation and progression in a quasi-unidirectional non-crimp fabric based fibre composite used for wind turbine blades. This is done by combining in situ transilluminated white light imagining (TWLI) with ex-situ X-ray computed tomography (CT) experiments along with tension clamp X-ray CT experiments. TWLI is used to monitor the off-axis cracks in the thin supporting backing fibre bundles present in quasi-UD composites, and a crack counting algorithm is applied to automatically count the cracks in images obtained in situ during fatigue testing. It is found that off-axis cracks not only initiate at the specimen edges but also at isolated locations inside the specimen, which could be related to the microstructural features. In addition, a clear effect of strain level on the measured off-axis crack density is observed. From the X-ray CT experiments, it is found that the UD fibre fractures initiate and progress from regions where the off-axis backing fibre bundles are ‘in contact’ with a UD fibre bundle. Damage is seen to first initiate at a cross-over region of the backing fibre bundles, and later at a region with only one backing fibre bundle. In addition, applying tension to the specimen during X-ray CT scanning is found to reveal additional UD fibre fractures that are not visible in scans performed the unloaded state. With load applied, a significant number of UD fibre fractures were observed earlier in the fatigue life than expected. Based on the observations of the study a damage progression scheme is presented for quasi-UD fibre composites.
AB - The current work studies the fatigue damage initiation and progression in a quasi-unidirectional non-crimp fabric based fibre composite used for wind turbine blades. This is done by combining in situ transilluminated white light imagining (TWLI) with ex-situ X-ray computed tomography (CT) experiments along with tension clamp X-ray CT experiments. TWLI is used to monitor the off-axis cracks in the thin supporting backing fibre bundles present in quasi-UD composites, and a crack counting algorithm is applied to automatically count the cracks in images obtained in situ during fatigue testing. It is found that off-axis cracks not only initiate at the specimen edges but also at isolated locations inside the specimen, which could be related to the microstructural features. In addition, a clear effect of strain level on the measured off-axis crack density is observed. From the X-ray CT experiments, it is found that the UD fibre fractures initiate and progress from regions where the off-axis backing fibre bundles are ‘in contact’ with a UD fibre bundle. Damage is seen to first initiate at a cross-over region of the backing fibre bundles, and later at a region with only one backing fibre bundle. In addition, applying tension to the specimen during X-ray CT scanning is found to reveal additional UD fibre fractures that are not visible in scans performed the unloaded state. With load applied, a significant number of UD fibre fractures were observed earlier in the fatigue life than expected. Based on the observations of the study a damage progression scheme is presented for quasi-UD fibre composites.
KW - A. Glass fibres
KW - A. Polymer matrix composites (PMCs)
KW - B. Fracture
KW - D. Non-destructive testing
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U2 - 10.1016/j.compositesa.2018.03.002
DO - 10.1016/j.compositesa.2018.03.002
M3 - Article
AN - SCOPUS:85054861474
SN - 1359-835X
VL - 109
SP - 481
EP - 497
JO - Composites Part A: Applied Science and Manufacturing
JF - Composites Part A: Applied Science and Manufacturing
ER -