Elsevier Vernet, N.; Ruiz, E.; Advani, S.; Alms, JB.; Aubert, M.; Barburski, M.; Barari, B.... (2014)
Abstract:In this second international permeability benchmark, the in-plane permeability values of a carbon fabric were determined by 12 participants worldwide. One other participant also investigated the deformation of this fabric. The aim of this work was to obtain comparable results in order to make a step towards standardization of permeability measurements of fibrous reinforcements. The procedures used by most participants were according to the guidelines defined for this exercise after the first benchmark. Unidirectional injections in three in-plane directions of the fabric were conducted to determine the unsaturated in-plane permeability tensor. Parameters such as fiber volume fraction, injection pressure and fluid viscosity have been fixed in order to minimize sources of scatter. The comparison of the results from each participant was encouraging. The scatter between data obtained while respecting the test guidelines was close to the scatter of the setups themselves. A slightly 2 higher dispersion was observed when some parameters differed from the recommendations.Overall, a good correlation is observed between all the results of this exercise.
The development of bio-based composites is essential in order to protect the environment while enhancing energy efficiencies. In the present investigation, the plant-derived cellulose nano-fibers (CNFs)/bio-based epoxy composites were manufactured using the Liquid Composite Molding (LCM) process. More specifically, the CNFs with and without chemical modification were utilized in the composites. The curing kinetics of the prepared composites was studied using both the isothermal and dynamic Differential Scanning Calorimetry (DSC) methods. The microstructure as well as the mechanical and tribological properties were investigated on the cured composites in order to understand the structure-property correlations of the composites. The results indicated that the manufactured composites showed improved mechanical and tribological properties when compared to the pure epoxy samples. Furthermore, the chemically modified CNFs reinforced composites outperformed the untreated composites. The surface modification of the fibers improved the curing of the resin by reducing the activation energy, and led to an improvement in the mechanical properties. The CNFs/bio-based epoxy composites form uniform tribo-layer during sliding which minimizes the direct contact between surfaces, thus reducing both the friction and wear of the composites.
A numerical methodology is proposed to predict void content and evolution during autoclave processing of thermoset prepregs. Starting with the initial prepreg void content, the void evolution model implements mechanisms for void compaction under the effect of the applied pressure, including Ideal Gas law compaction, and squeeze flow for single curvature geometries. Pressure variability in the prepreg stack due to interactions between applied autoclave pressure and anisotropic material response are considered and implemented. A parametric study is conducted to investigate the role of material anisotropy, initial void content, and applied autoclave pressure on void evolution during consolidation of prepregs on a tool with single curvatures. The ability of the model to predict pressure gradient through the thickness of the laminate and its impact on void evolution is discussed.
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