Zhe Gao

A review on the impact tension behaviors of textile structural composites

The three-dimensional textile composites have excellent advantages of impact resistance, owing to their more integral microstructure and higher interlaminar shear strength than those of laminated composites. The composites are frequently used under impact loading in the practical application. Researches on the impact behaviors can help in the development and optimization of design for textile structural composites. In this review, the development and features of three types of textile structures, including weaving, knitting, and braiding have been introduced respectively, and the current and future potential applications of these kinds of textile structural composites have been described. The impact tension behaviors and the damage mechanisms of textile structural composites have been introduced. The finite element analysis and frequency domain analysis which to reveal the tensile damage mechanisms of textile structural composites under high strain rates also have been investigated. Furthermore, the future development of impact tension behaviors of textile structural composites is also introduced in this review.

Knitting Technologies And Tensile Properties Of A Novel Curved Flat-Knitted Three-Dimensional Spacer Fabrics

Abstract This paper introduces a knitting technique for making innovative curved three-dimensional (3D) spacer fabrics by the computer flat-knitting machine. During manufacturing, a number of reinforcement yarns made of aramid fibres are inserted into 3D spacer fabrics along the weft direction to enhance the fabric tensile properties. Curved, flat-knitted 3D spacer fabrics with different angles (in the warp direction) were also developed. Tensile tests were carried out in the weft and warp directions for the two spacer fabrics (with and without reinforcement yarns), and their stress–strain curves were compared. The results showed that the reinforcement yarns can reduce the fabric deformation and improve tensile stress and dimensional stability of 3D spacer fabrics. This research can help the further study of 3D spacer fabric when applied to composites.

Tear properties and meso-scale mechanism of multi-axial warp-knitted fabric from various architectures: Studied by photography

Tear properties tests of three kinds of multi-axial warp-knitted (MWK) fabric: triaxial fabrics (−45 °/90 °/+45 ° and −45 °/0 °/+45 °) and biaxial fabric (−45 °/+45 °) were respectively implemented along the orientations of 0 °, 45 ° and 90 °. Load-displacement curves were well obtained. The high-speed camera was employed to observe the whole tear damage process and series of still images were picked up to analyze the meso-scale mechanism of the extension and displacement of tows on oriented layers. The results indicated the tear properties of MWK fabric are closely related to the orientations of the layers and the deformation mechanism of the layers. Stitching yarns incarnated significant effects in restricting the deformation procedures of tows.

Transverse impact characterization of carbon woven fabric-foam sandwich composites with carbon nanotubes

Different contents of carbon nanotubes were incorporated in an epoxy matrix that was then reinforced with carbon woven fabric and foam to manufacture the carbon woven fabric-foam sandwich composites. The transverse impact characterizations of the sandwich composites were reported. The split Hopkinson pressure bar apparatus were employed to test the transverse impact behaviors. The impact wave signals were recorded and the impact load versus displacement curves and impact damages of the sandwich composites were observed to analyze the energy absorption and the impact damage mechanisms. It was found that the failure area and energy absorption is increased as the increase of impact velocity and decrease of carbon nanotubes content. The main failure modes are foam breakage and the interface delamination between the woven fabric and foam.

Tension and Tear Behaviors of Co-woven-knitted Fabric with Photograph Investigation

Co-woven-knitted (CWK) fabric is a novel structural fabric which combines the woven and knitted structures together. In this paper, the tension and tear properties of CWK fabric along different directions are tested. The stress-strain curves for tension loading and load-displacement curves for tearing loading were well obtained. The high-speed camera also was employed to observe the whole damage process and series of still pictures were picked up to analyze the meso-scale mechanism of CWK fabric along various directions. The results indicated that the tension and tear properties of CWK fabric are closely related to the directions of loading.

Experimental investigation on the quasi-static penetration behavior of curved multi-axial warp-knitted composites

The quasi-static penetration tests of the curved glass/phenolic multi-axial warp-knitted (MWK) composites with two types of preform structures and in three different curvatures were implemented. Three phases — elastic deformation phase, progressive damage phase and tension-shear phase were identified to present the different damage behavior stages of curved glass/phenolic MWK composites under quasi-static penetration. Several types of damage modes including matrix cracking, tension-shear of the materials, fiber fracture and interlayer delamination were revealed based on the load-displacement curves and morphology analyses. The results showed that the reinforcement structure and the curvature of the specimens did provide obvious influence onto the quasi-static penetration behaviors of curved glass/phenolic MWK composites and they could be utilized in pointed purposes according to the different mechanical features.

Preparation and performance as PEM of sulfonated pre-oxidized nanofiber/SPEEK composite membrane

Building proton transfer channel is an important strategy to optimize the proton transfer process of the proton exchange membrane (PEM). In this work, sulfonated pre-oxidized nanofibers were prepared by solution blowing of polyacrylonitrile (PAN) nanofibers followed by pre-oxidization and sulfonating, and the nanofibers were composited with SPEEK to enhance its performance as PEM. The results of the proton conductivity verified that the employment of sulfonated pre-oxidized nanofibers improved the proton conductivity. Meanwhile, the introduction of the sulfonated pre-oxidized nanofibers realized the upgrades of the thermostability and water absorbency of the membrane, and led to the decrease of the swelling property and methyl alcohol’s permeability of the material. It is indicated that the composite membrane is promising materials for PEM fuel cells.

Comparative study on the mechanical behavior of carbon weft-knitted biaxial fabrics stitched by polyester fibers and preoxidized polyacrylonitrile fibers

The carbon weft-knitted biaxial fabrics stitched by polyester fibers and preoxidized polyacrylonitrile fibers were prepared respectively. Tensile and tearing tests of two types of carbon biaxial weft-knitted fabrics stitched by different fibers were carried out. Stress–strain and load–displacement curves were obtained according to the testing data. The high-speed camera was employed to observe the whole testing process and series of still images were picked up according to the time nodes to analyze the meso-scale mechanism of the extension and displacement of tows on oriented layers and stitching yarns. The properties of the two fabrics were compared based on the research of the stitching yarns mechanical performance. The researching results indicated that preoxidized polyacrylonitrile fiber exhibit higher mechanical behaviors, and its fabric bond displays excellent performance.