Guidelines for the use of organic sheets (continuous fiber reinforced thermoplastic sheets)

The organic sheet is a continuous fiber reinforced thermoplastic sheetmainly composed of carbon fiber or glass fiber fabric. Recently, organic sheets have begun to be more widely used in semi-finished products. These semi-finished products have the key advantages of thermoplastic matrix (from polypropylene and polyamide 6 to polyethyleneimine) and different structures brought about by reinforcing fibers.

Seniors in the composites industry often refer to organic sheets as thermoplastic prepregs, because this can intuitively describe organic sheets as continuous FRP thermoset composites encountered in structural applications by analogy. Organic sheets have a powerful inherent advantage: they contain fully polymerized thermoplastic polymers (organic materials). Unlike prepregs, which have a limited shelf life, require refrigeration and specific inventory control, organic sheets can be stored for longer periods of time under general temperature and relative humidity conditions through the thermoplastic polymer they contain. Organic sheets can be cut into shapes, stacked, and integrated into automated manufacturing processes similar to sheet metal processing. This similarity to sheet metal—often referred to as blanks by metal part press molders—is particularly useful when discussing applications with stakeholders in the automotive industry.

Industries such as sporting goods and consumer goods have adopted organic sheets for a long time because of their large production volumes and short cycle times. These requirements also generally exist in the automotive industry, where the application of organic sheets is becoming more and more complex. Leading equipment manufacturers have proven the maturity of organic sheet technology and are delivering processing units that can produce more than 200,000 parts per year from one production line.

Organic sheets can be used in thermoforming, compression molding or hybrid molding processes. If you are new to organic sheets, or related processes appear in your work, experimenting with these multifunctional composite materials may be easier than you think. Here are some tips for getting started:

Start with what you have-use existing equipment and tools and contact the material manufacturer to get guidance on processing steps and conditions, including mold preparation (if you have special requirements for surface quality). The organic sheet must be heated above the melting point of the polymer before it can be plasticized. If you do not have a heat source for the thermoforming operation, consider adding a low-cost infrared heater to preheat the sheet before placing it in the mold. When experimenting with new thermoplastic composites, always consider proper ventilation.

Choose the organic sheet suitable for the application-all organic sheets are different. Choosing the appropriate configuration is very important for processability, performance and final cost. The organic sheet is defined by the thermoplastic polymer, fiber reinforcement type, fiber structure (unidirectional, woven fabric, non-crimp fabric, etc.) and sheet thickness. A sheet may contain one or more layers.

The operating temperature and environmental conditions required for the application will determine the polymer selected. The complexity of parts, drape and load requirements will guide the selection of steel and fiber structures. The organic sheet based on woven fabric has good drape. Organic sheets based on non-crimp fabrics (NCF) will allow more flexible designs based on load paths and may save weight, but will increase costs.

Pay attention to load requirements-understanding load requirements is very important to control material cost and quality. If 2mm thick organic sheets based on complex NCF fabrics or thicker organic sheets based on woven fabrics can be used to solve the critical load path, the higher-cost NCF organic sheets may make the overall solution more cost-effective and lightweight. Organic sheets reinforced with partial unidirectional tapes are also an elegant solution, helping to balance cost and quality.

Use simulation and check all assumptions-use simulation as early as possible to optimize the design. Nowadays, software vendors can guide you through features designed specifically for organic sheets, making screening very approachable. In order to obtain accurate results, it is important to understand and utilize the orthotropic properties of these materials (the unique behavior in the x-axis, y-axis, and z-axis directions). For example, when an organic sheet based on a 2/2 twill or plain weave fabric exhibits similar performance in both directions (warp and weft), the assumption of isotropy will be incorrect.

Jiuheng Chen, a design engineer at Forward Engineering GmbH, explained this very simply. If the organic sheet is isotropic, the shear modulus can be calculated using the elastic model and Poisson's ratio as E/2(1+n) = 24,000/2(1+0.15) = 10,435 MPa. In fact, the material is orthotropic and the shear modulus is about 3200mpa, which should be used as a benchmark for modeling.

Get in touch with your network-use a collaborative environment in the composites industry value chain. Providing composite solutions requires a solid understanding of materials, processes, design, and manufacturing costs. A good network of partners helps to get answers to questions as early as possible and focus on solutions that are most likely to succeed.

Although the basic characteristics of organic sheet materials such as light weight, recyclability, fast processing speed, and suitability for mass applications have been more emphasized, these characteristics have a core feature that can speed up the implementation process. This feature makes mass production The industry is able to provide new products faster, customize personalized models, and combine multiple design features.

Organic sheets can achieve a large number of functional integrations from brackets and metal inlays to sensors and electromagnetic interference shielding solutions. Thermoplastic solutions centered on organic sheets are easy to sample, can significantly reduce the number of parts, reduce mold costs, and can be extended to mass production. The core advantages of organic sheets will bring the greatest value to the application.

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