SAKAI OVEX is a Japanese company dedicated to the research and development of carbon fiber open fiber (spreading) technology and product production. As early as around 2010, the company cooperated with Japan's Toho Tennax (now Teijin) to develop ultra-lightweight carbon fiber products, which are half as light as the thinnest carbon fiber products after the carbon fiber open fiber treatment.
This paper first introduces the excellent characteristics of carbon fiber materials, and then focuses on the characteristics of carbon fiber open-fiber technology, as well as open-fiber carbon fiber and its composite material performance advantages are described, and finally combined with the SAKAI OVEX company's current carbon fiber open-fiber yarn in the form of the main products are briefly described.
01, the excellent characteristics of carbon fiber
Carbon fiber is not only light, strong, corrosion resistance and other characteristics, but also has excellent electrical conductivity, heat resistance, dimensional stability, chemical stability.
Mechanical/dynamic properties:
Small specific gravity (1.7 to 2.0) and lighter than metals, etc.
High modulus of elasticity (200 to 650 GPa) and high rigidity.
High strength (3000MPa to 7000MPa).
Excellent vibration attenuation.
Anisotropic material, allowing appropriate structural design for the purpose.
Thermal Properties:
Excellent heat resistance in inert atmosphere.
Small coefficient of thermal expansion and good dimensional stability.
Possesses thermal conductivity.
Electromagnetic properties:
With electromagnetic wave shielding.
Good permeability to X-rays.
Chemical properties: excellent chemical resistance.
Electrical properties: has a certain degree of electrical conductivity.
02, carbon fiber open fiber technology and advantages
Open fiber technology: also known as yarn spreading technology, it is the carbon fiber tow in a wide range of thin and uniformly spread to create open fiber yarn technology. Carbon fiber is a bundle of thousands to tens of thousands of filaments with a round or slightly flat cross-section. After unfolding, thousands to tens of thousands of filaments are spread across the width with a flattened cross-section. The figure below shows a cross-section of the inside of a carbon fiber tow before and after spreading.
Fabrics using carbon fiber open fiber yarns have the following main advantages:
Realization of thin ply, reduction of crimp angle, and improvement of mechanical properties
a), uniform resin dispersion due to small crimp
The following figure compares the structural diagrams of laminates processed using carbon fiber fabrics before and after carbon fiber opening, where the left side shows the structural diagram before carbon fiber opening, and the resin-rich portion is unevenly distributed in laminates using conventional carbon fiber fabrics (3K). And in the laminate made of carbon fiber open fiber yarn fabric on the right, the resin and carbon fiber are uniformly dispersed, and the mechanical properties are improved.
b) Improve the straightness of carbon fibers to bring out the performance of the fibers to the limit.
Carbon fiber tow without open fiber treatment is thicker, the surface is more concave and convex, due to the bending of the fiber tow, the strength is reduced, the resin impregnation is poor, and it is easy to peel off between layers (as shown in the following left figure). After open-fiber treatment, the carbon fiber tow is internally thin, light, unevenly decreased concavity and convexity, and the weaving angle is small. It has excellent resin impregnation properties and is not easy to peel off between layers, and therefore shows high physical property values such as fatigue properties (as shown in the right figure below). Therefore, after the open fiber treatment, the fiber prayer is smaller, and it can relieve the stress concentration.
c), will not produce inter-layer peeling due to transverse cracks.
Laminated materials made of traditional carbon fiber and its fabrics are prone to transverse cracks and delamination between layers (as shown in the left figure below); after open-fiber treatment, laminates prepared using carbon fiber spread fabrics are less prone to transverse cracks and interlaminar peeling (as shown in the right figure below), which results in improved fatigue strength.
Improved tensile, flexural and interlaminar shear strength of CFRP laminates using carbon fiber open weave fabrics
03,Common Carbon Fiber Open Fiber Products
3.1 Carbon fiber open fiber yarn
After open fiber treatment, 12K～48K specification PAN grade carbon fiber tows can be continuously open fiber to a width of 2～40mm, and according to the type of carbon fiber, the range of open fiber width is also different.
Carbon fiber open fiber yarn.
3.2 Carbon fiber open fiber fabric
Carbon fiber after fiber opening can be used for warp knitting, weft knitting and other fabrics, forming a thinner structure than the previous carbon fiber textiles, formability (resin impregnation) and physical properties to improve.
Carbon fiber textile before and after fiber opening
3.3 Carbon fiber open-fiber prepregs
Depending on the application, various types of intermediate materials such as prepreg/semi-preg can be processed, and the type of impregnating resin can be changed, such as thermosetting resin or thermoplastic resin.
Prepreg: A base material for CFRP (Carbon Fiber Reinforced Plastic) molding made by impregnating carbon fiber open fiber yarns or open fiber fabrics with a thermosetting resin or thermoplastic resin. Since it is impregnated with resin, it can be used for short-term hot press molding.
Semi-impregnated: A CFRTP (Carbon Fiber Reinforced Thermoplastic) molding base material made by laminating a thermoplastic resin film onto open fiber yarn or open fiber fabric. Due to its flexibility, it is a material with high moldability and can be molded into CFRTP by hot pressing.
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