The stab resistance of thermoset(TS) impregnated, woven UHMWPE fabric with additional steel fabrics was investigated under dynamic stab testing conditions. Vinyl-ester resin was coated on the UHMWPE fabrics with hand lay-up process to fabricate the composite and the mental fabrics were laminated on the composites. Dynamic stab testing of targets was based on GA68-2008 for stab resistance of body armor. Six uniform specified knives impactor were used for testing. And the samples are found to present significant improvements in stab resistance (knife threat) over neat fabric targets of equal areal density. Photographs show that resin primarily reduces the mobility of yarns and enables them to stop the knife penetration more effectively in the damage zone. These results indicate that the penetration of knives through such multilayer fabrics is effectively prevented and the process could be used to fabricate flexible body armors that provide improved protection against stab threat.
Based on the principle and fabricating process of Quasi-Isotropic braided composites, the regular pattern of movement of each yarn is analyzed and the inner unit cell model is established in this paper. The real Quasi-Isotropic braiding structure is built using 3D paint software named UG NX4.0. Compressive mechanical properties of 3D Quasi-Isotropic braided composites are also discussed. It is found that the load–deflection curve of the Quasi-isotropic braided composites displays a relatively linear behavior, behaving mostly as the characteristics of shear.
Woven unit-cell geometry functions are presented for a balanced plain weave fabric. Based on the functions, a 3D geometrical model applying to a meshing preprocessor for 3D finite element is proposed. The geometry model takes into account the existence of the space between tows, the undulation of the tow, and the actual tow cross-section shape. The internal geometry of model is from micrographs of sectioned laminates, which is helpful to define the accurate and actual 3D geometrical model. The section shape of the yarn remains unchanged along the trajectory. This model can be easily identified using three parameters measured on a real fabric. An accurate hexahedral mesh developed using these geometry model is presented. This is an important point for 3D finite element simulation of fabric model, which is a powerful method to investigate the mechanical behavior and also the composites made from it.
Six different kinds of fabrics were weaved using the 2.5D woven fabrics with warp-stuffer, The three point beam test method was employed to test bending behavior. The effect of yarn count, yarn fineness, fabric layers on the bending behavior of fabrics was analyzed. The results showed that warp and weft load, flexural stress, flexural strain and flexural modulus were increased as the yarn counts increasing; Warp and weft load, flexural stress and flexural strain increases as the fabric layers increased, flexural modulus decreased as the fabric layers increasing; load, flexural stress, flexural strain and flexural modulus increased as the yarn linear density increasing.
The Fe3+,La3+ co-doped polyvinyl acetate(PVAc)/titanium dioxide(TiO2) composite nanofibers were firstly prepared by combining sol-gel method and electrospinning process, and then calcined under 300°Cand 600°C separately. The effect of calcination temperature on structures, surface morphologies, crystalline state, elemental composition and photocatalysis activity were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), X-ray Diffraction (XRD) , energy dispersive X-ray spectroscopy (EDX) and ultraviolet-visible spectrophotometer(UV-Vis) respectively. The SEM and AFM images showed that the nanofibers were randomly distributed to form the fibrous web, the diameters and surface roughness of nanofibers were obviously changed as the calcination tempreture increasing. The EDX analysis and XRD spectra indicated the percentage of C,O,Ti elements varied as the increase of tempreture and the formation of anatase crystal form TiO2 nanofibers under 600°C.The UV-Vis curves revealed strong adsorption to methylene blue under 600°C calcination.
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