Liquid Absorption in Composite
Pham, Trang (2020)
Pham, Trang
2020
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2020090120003
https://urn.fi/URN:NBN:fi:amk-2020090120003
Tiivistelmä
This thesis work aims to study the water absorption in composite materials including wood and composites/thermosetting resin under condition of room temperatures and atmospheric pressures. The testing specimens for water absorption in composite were prepared following to the standard measurement of ASTM D570 and ISO 62. The composite laminate used in this research was built from glass fibers and the resin of vinyl-ester ATLAC E Nova M6215. The data sheet of this resin shows a noticeable value of water absorption property which need to be measured. At first, the study of water absorbed into wood samples of Balsa and Birch was conducted by immersing the samples in tap water until the saturation point. The process of water absorption in the samples of wood was found to approach the behavior of non-Fickian diffusion. The resulting data observed by the mass change during soaking time is analyzed and modeled following to the mathematical viewpoint of Fick’s law diffusion and the empirical model of Peleg. The diffusion coefficient to evaluate the water uptake in two different wood materials of Birch and Balsa, were determined as 8.23x10-4 and 5.67x10-3 m2/s, respectively. Besides, the resulting parameter of non-linear regression analysis according to Peleg model was also obtained. The value of root mean square error (RMSE) demonstrates the better suitability of Peleg model for modelling the experiment data of water absorption in case of Birch wood (RMSE of 12.47 %) comparing to the case of Balsa wood (RMSE of 84.6%).
For the study of water absorption in composite/thermosetting resin samples, the alternative spectroscopic methods including UV-visible spectrophotometry and Fourier Transform Infrared Spectroscopy (FTIR) were investigated. The resulting spectra from the UV-visible-NIR spectrophotometer for specimens of vinyl ester resin indicate the effect of water molecules in the wavelength of 300 nm to 360nm. In the other hand, the outcome spectra of composite resin samples by using method of FTIR point out the evident impact of water to composite samples for a long period of soaking time. Two regions wavenumber involved to the increment of water absorption in composite resin samples include: the wavenumber from 2840 cm-1 to 3500 cm-1, which is known as the region of OH stretching; and the wavenumber from 1630 cm-1 to 1780 cm-1 which corresponds to the bending vibration mode of water molecules existed in composite structure. Furthermore, the impact of different grinding paper grits when polishing the surface of composite samples was also performed by the FTIR spectra. In general, the intensity of absorbance peaks in OH stretching region intends to increase when increasing the polishing protocol on surface of composite samples. After 15 days of exposure in water, composite samples polished by paper grit of 4000 has a highest increase of absorbance intensity with 470% at the peak 2924 cm-1, while the sample polished by the paper grit of 320 has the lowest increase of intensity with 260%.
For the study of water absorption in composite/thermosetting resin samples, the alternative spectroscopic methods including UV-visible spectrophotometry and Fourier Transform Infrared Spectroscopy (FTIR) were investigated. The resulting spectra from the UV-visible-NIR spectrophotometer for specimens of vinyl ester resin indicate the effect of water molecules in the wavelength of 300 nm to 360nm. In the other hand, the outcome spectra of composite resin samples by using method of FTIR point out the evident impact of water to composite samples for a long period of soaking time. Two regions wavenumber involved to the increment of water absorption in composite resin samples include: the wavenumber from 2840 cm-1 to 3500 cm-1, which is known as the region of OH stretching; and the wavenumber from 1630 cm-1 to 1780 cm-1 which corresponds to the bending vibration mode of water molecules existed in composite structure. Furthermore, the impact of different grinding paper grits when polishing the surface of composite samples was also performed by the FTIR spectra. In general, the intensity of absorbance peaks in OH stretching region intends to increase when increasing the polishing protocol on surface of composite samples. After 15 days of exposure in water, composite samples polished by paper grit of 4000 has a highest increase of absorbance intensity with 470% at the peak 2924 cm-1, while the sample polished by the paper grit of 320 has the lowest increase of intensity with 260%.