Now showing1 - 2 of 2
- Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Load‐Induced Shear Band Formation in Microscale Epoxy Materials(Wiley, 2025-03-31); ; ; ; Thermosetting polymer thin films exhibit distinct mechanical behaviors at the microscopic scale compared to bulk materials. Experimental results reveal significant necking and unexpected shear band formation under tensile load. This study investigates the mechanisms underlying shear band formation in epoxy resin systems composed of bisphenol‐diglycidyl‐ether and diamines. Mechanical testing methods, including creep, relaxation, and cyclic testing, as well as ex situ and in situ high‐resolution infrared (IR) spectroscopy, are used synergistically with quantum mechanical calculations to elucidate the underlying molecular mechanisms. Additionally, molecular dynamics (MD) simulations on a nanoscale model explored the (visco‐)plastic behavior and network strain in epoxies. Our findings reveal a strong correlation between shear band formation and shifts in IR spectra, specifically the redshift of para‐phenylene and the blueshift of out‐of‐plane vibrations of aromatic moieties. These shifts are attributed to load‐induced aromatic stretching in the polymer backbone. The robust agreement between experimental data and simulation results supports these observations at both the atomic and nanoscale. These insights enhance the understanding of epoxy resin mechanics, potentially informing the design of advanced composite materials.Publicationtype: Journal Article102 26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Performing Polarized Raman and Digital Image Correlation Analysis to Understand the Increased Ductility of Microscale Epoxy Materials(Wiley, 2025-03-27); ; ; ; The highly cross‐linked (epoxy) matrix material in fiber reinforced polymers has a microscopic volume between fibers and therefore exhibits different mechanical behavior in comparison to standard bulk epoxy samples. It has been found in previous studies that a decreased epoxy gauge volume leads to an increased deformation ability (necking and shear band formation). By using laser cutting to create dogbone samples from manufactured epoxy films, the gauge volume can be further reduced in comparison to previous studies, and the ductility can be enhanced even further. To understand load‐induced molecular mechanisms responsible for the increase in ductility at macroscale, this study combines digital image correlation (DIC) with tensile tests and precise force measurement. The global and local strains are calculated using the DIC data. The determined strains reach values up to 80% (global strains) and 120% (local strains), respectively. These strain values are significantly higher than those of archetypical brittle epoxy bulk samples (less than 10%). Polarized Raman spectra show that load‐bearing backbone molecules in the deformed film sample regions are oriented in the tensile load direction. This orientation might be due to the unraveling of entanglements, which can be seen as a sudden decrease followed by a subsequent rise in engineering stress values during deformation.Publicationtype: Journal Article36 19