Low temperature fatigue crack propagation in toughened epoxy resins aimed for filament winding of type V composite pressure vessels

In this study, application relevant toughened epoxy-amine formulations were investigated regarding their mechanical behavior at low temperatures and compared to a non-toughened reference. The application-oriented resins are based on reactive diluent-modified diglycidylether of bisphenol A (DGEBA) which were tested at 22 °C and −50 °C in regard to their fracture toughness (KIC) and fatigue crack propagation (da/dN) behavior. The E′ and E’’ moduli and the corresponding glass transition temperatures Tg were determined via dynamic mechanical thermal analyses (DMTA) which also described the influence of the block copolymeric toughener on the epoxy resin network. The plastic zone size, calculated during crack propagation, reveals the temperature dependent toughener-matrix interaction. The prevailing energy dissipation mechanisms were correlated with the changes of E’. SEM micrographs confirm the superior performance of the toughened system at −50 °C by the decrease of the fatigue cack propagation slopes and highlight the trends of the materials low temperature behavior

Multiscale Structural Characterization of Biobased Diallyl–Eugenol Polymer Networks

International audienceBiosourced eugenol-based polymer networks have a potential functionality for antibacterial coating applications. The presence of carvacrol, a phenol compound, exacerbates these properties. However, the relationship between the network structure and the macroscopic thermomechanical behavior is not known for these biopolymers. Thus, this work details a robust study of this relationship through a multiscale experimental approach combining Dielectric spectroscopy, DMA, Tensile testing and Time domain DQ 1 H NMR. It was shown that carvacrol has an influence on the molecular mobility of the materials. Namely it induces the appearance of a shouldering on the γ relaxation and a diminishing of T α. More surprisingly, up to 20% wt , carvacrol increases the elastic E and Young's E moduli. This observation can be interpreted as an increase of the crosslink density ν C of the networks. Time domain DQ 1 H NMR shows that the 1 residual dipolar coupling constant D res also increases. Thus, carvacrol seems to act as both a thermal plasticizer and a mechanical reinforcement, which may seem to be antagonistic trends. For carvacrol contents over 20% wt these properties diminish due to a saturation of this molecule in the networks and the onset of a phase separation. By combining the aforementioned techniques, it was proven that carvacrol linearly increased the measured crosslink density and thermomechanical properties by physically bonding to the networks through π − π interactions. These interactions would act as physical crosslinks. This work demonstrates that by correlating the results of various multiscale experimental techniques, a better comprehension of the structure-property relationship can be established for biobased functional polymer networks

Design of macroporous photo-cationically cured resorcinol-based epoxy resins coupled to a solid template technique

International audienc

Dual UV-Thermal Curing of Biobased Resorcinol Epoxy Resin-Diatomite Composites with Improved Acoustic Performance and Attractive Flame Retardancy Behavior

International audienc