Reference - Compression molding of long chopped fiber thermoplastic composites
| Type | Journal |
|---|---|
| Title | Compression molding of long chopped fiber thermoplastic composites |
| Abstract | [[Abstract::When it comes to fabricating advanced composite structures, there is an array of fabrication processes available. However, when part complexity increases, performance is demanding and higher volume production rates are required the field begins to narrow. One such method that meets these criteria is compression molding with long chopped fiber thermoplastics. Compression molding is the process by which a charge of fiber reinforced prepreg bulk molding compound (BMC) is molded under heat and high pressures to form complex shaped parts. The BMCs under discussion are created by chopping existing unidirectional fiber reinforced thermoplastic tape into long lengths [6.4mm to 50.8mm (0.25 inch to 2.0 inch)]. These loose chips or strands are then weighed out to the exact amount required to fill the volume of a given tool, placed in a matched metal mold and heated and compressed to pressures that force the fibers to flow into the mold cavity, filling in every complex feature before cooling. Thermoplastic BMC compression molding requires a degree of mold temperature control not normally required by thermoset compression molding. TenCate/CCS uses a tooling concept called XPress to tightly control the mold temperature in zones over the surface of the part. Flat plates and a carbon fiber/thermoplastic bracket with complex features has been molded using this process. Structural test coupons have been molded and tested for stiffness and strength characterization. State-of-the-art design and analysis routines are now available to aid in the design of parts using these BMC materials.]] |
| Authors |
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| Date | 2014 |
| Issue | Figure 1 |
| Journal | CAMX 2014 - Composites and Advanced Materials Expo: Combined Strength. Unsurpassed Innovation. |
Welcome
Welcome to the CKN Knowledge in Practice Centre (KPC). The KPC is a resource for learning and applying scientific knowledge to the practice of composites manufacturing. As you navigate around the KPC, refer back to the information on this right-hand pane as a resource for understanding the intricacies of composites processing and why the KPC is laid out in the way that it is. The following video explains the KPC approach:
Understanding Composites Processing
The Knowledge in Practice Centre (KPC) is centered around a structured method of thinking about composite material manufacturing. From the top down, the heirarchy consists of:
- The factory
- Factory cells and/or the factory layout
- Process steps (embodied in the factory process flow) consisting of:
The way that the material, shape, tooling & consumables and equipment (abbreviated as MSTE) interact with each other during a process step is critical to the outcome of the manufacturing step, and ultimately critical to the quality of the finished part. The interactions between MSTE during a process step can be numerous and complex, but the Knowledge in Practice Centre aims to make you aware of these interactions, understand how one parameter affects another, and understand how to analyze the problem using a systems based approach. Using this approach, the factory can then be developed with a complete understanding and control of all interactions.
Interrelationship of Function, Shape, Material & Process
Design for manufacturing is critical to ensuring the producibility of a part. Trouble arises when it is considered too late or not at all in the design process. Conversely, process design (controlling the interactions between shape, material, tooling & consumables and equipment to achieve a desired outcome) must always consider the shape and material of the part. Ashby has developed and popularized the approach linking design (function) to the choice of material and shape, which influence the process selected and vice versa, as shown below:
Within the Knowledge in Practice Centre the same methodology is applied but the process is more fully defined by also explicitly calling out the equipment and tooling & consumables. Note that in common usage, a process which consists of many steps can be arbitrarily defined by just one step, e.g. "spray-up". Though convenient, this can be misleading.
Workflows
The KPC's Practice and Case Study volumes consist of three types of workflows:
- Development - Analyzing the interactions between MSTE in the process steps to make decisions on processing parameters and understanding how the process steps and factory cells fit within the factory.
- Troubleshooting - Guiding you to possible causes of processing issues affecting either cost, rate or quality and directing you to the most appropriate development workflow to improve the process
- Optimization - An expansion on the development workflows where a larger number of options are considered to achieve the best mixture of cost, rate & quality for your application.
