Analysis of the Porosity Changing after Moisture Absorption in Functional Knitted Fabrics

The paper analyses the effect of stitch geometrical modality changing after moisture absorption on the porosity of knitted fabrics,and educes the formulas between porosity and stitch parameters.Regarding as the cell stitch,the increasing of yarn diameter brings the porosity decreasing and the fabric shrinking in the wale direction.While the diameter keeps invariability,the yarn elongating brings the fabric humping up as well as the increasing porosity.The air-permeability experiments have been conducted to validate the theoretical analysis,and there is reasonable agreement between the theories and experiments.

Influence of Overlay Placement and Fabric Architecture of Non-crimp Fabrics on In-plane and Transverse Permeability in Liquid Composite Molding

To study the resin flow and the permeability in fabric preforms during the liquid composite molding( LCM) process,influences of stitch and overlay placement styles on the internal flow behavior in-plane and transverse were investigated. The permeability tests were carried using unidirectional and biaxial noncrimp carbon fabric( NCF) by linear capacitance sensors and ultrasound monitor system. The results indicate that the internal flow behavior and permeability in plane with different stitch and overlay placement styles are significantly different. When flow channels formed by stitches penetrate along the fiber direction,the permeability is high in one direction, which makes the in-plane principle permeabilities K_1 and K_2 significantly different. When there is an angle between the flow channel and fiber direction,the in-plane principle permeabilities on all directions are nearly the same and the flow process is close to isotropy. As to transverse permeability,the exist of flow channels on thickness influences it greatly and it is about 1-2 orders of magnitude lower in unidirectional fabric than that in biaxial NCF.

Enhanced absorption of Ag diamond-type nanoantenna arrays

The optical metal nanoantenna on thin film solar cell is effective to enhance light absorption. In this paper, the diamond-type Ag nanoantenna arrays are proposed for increasing the efficiency of solar cells by localized surface plasmons resonance(LSPR). The effect of metal nanoantenna on the absorption enhancement is theoretically investigated by the finite difference time domain(FDTD) method. Broadband absorption enhancements in both visible and near-infrared regions are demonstrated in case of solar cell with diamond-type Ag nanoantennas. The spectral response is manipulated by geometrical parameters of the nanoantennas. The maximum enhancement factor of 1.51 for solar cell is obtained. For comparison, the other three nanoantennas are also analyzed. The results show that the solar cell with optimized diamond-type nanoantenna arrays is more efficient in optical absorption.