Composites Manufacturing - Materials, Product, and Process Engineering Part 10 pps

© 2002 by CRC Press LLC This is the only thermoplastic manufacturing process used in industry for making structural thermoplastic composite parts. The process is used for making bumper beams, dashboards, kneebolsters, and other automotive structural parts. Figure 6.85 shows an automotive rear bumper beam having 5-mph capability. A painted kneebolster with molded-in texture to provide a Class A interior surface and heavy-truck dashboard are shown in Figure 6.86. Figure 6.87 shows an automotive seat back with part thickness less than 2 mm. Cut-outs are recycled for reuse. Consumer items such as office chairs (Figure 6.88) and helmets are also made using this process. 6.9.3.2 Basic Raw Materials The raw material for thermoplastic compression molding process is GMT (glass mat thermoplastics). GMT is primarily made from polypropylene resin and continuous but randomly oriented glass fibers. Melt-impregnated GMT is the most common material form. Powder-impregnated, discontinuous fiber reinforced GMT is also used. A sheet of fiber glass impregnated with polypropylene is used in this process. These materials are available in pre-cut, pre-weighed pieces of sheet composite materials, called blanks, for processing. TABLE 6.6 Part Cycle Time for Various Manufacturing Processes Manufacturing Process Part Cycle Time (s) Compression molding of GMT Injection molding Compression molding of SMC Blow molding SRIM 30–60 20–60 80–150 60–140 120–240 FIGURE 6.85 Automotive rear bumper beam. (Courtesy of Azdel Inc.) © 2002 by CRC Press LLC This is the only thermoplastic manufacturing process used in industry for making structural thermoplastic composite parts. The process is used for making bumper beams, dashboards, kneebolsters, and other automotive structural parts. Figure 6.85 shows an automotive rear bumper beam having 5-mph capability. A painted kneebolster with molded-in texture to provide a Class A interior surface and heavy-truck dashboard are shown in Figure 6.86. Figure 6.87 shows an automotive seat back with part thickness less than 2 mm. Cut-outs are recycled for reuse. Consumer items such as office chairs (Figure 6.88) and helmets are also made using this process. 6.9.3.2 Basic Raw Materials The raw material for thermoplastic compression molding process is GMT (glass mat thermoplastics). GMT is primarily made from polypropylene resin and continuous but randomly oriented glass fibers. Melt-impregnated GMT is the most common material form. Powder-impregnated, discontinuous fiber reinforced GMT is also used. A sheet of fiber glass impregnated with polypropylene is used in this process. These materials are available in pre-cut, pre-weighed pieces of sheet composite materials, called blanks, for processing. TABLE 6.6 Part Cycle Time for Various Manufacturing Processes Manufacturing Process Part Cycle Time (s) Compression molding of GMT Injection molding Compression molding of SMC Blow molding SRIM 30–60 20–60 80–150 60–140 120–240 FIGURE 6.85 Automotive rear bumper beam. (Courtesy of Azdel Inc.) © 2002 by CRC Press LLC 7 Process Models 7.1 Introduction Models are used to simulate real-world situations in a mathematical and graphical form to analyze a problem or to demonstrate the behavior and characteristics of the real world under various conditions. Engineers and researchers are using models to solve various types of physical, chemical, and engineering problems. Chemical plants control various chemical reac- tions and operations with the help of models. Physicists use various atomic models and quantum mechanics to understand a phenomenon. Material scientists use body-centered cubic (BCC), face-centered cubic (FCC), and other crystal structures to understand the behavior of metals and polymers. Metallurgists use phase diagrams, mechanical engineers use free body dia- grams and other models to describe or predict a phenomenon or real-world situation. Models are very useful for solving real engineering or physical problems without performing any experiment. In this chapter, models for composites manufacturing processes are described to gain more insight into these manufacturing processes. 7.2 The Importance of Models in Composites Manufacturing A process model is very helpful in analyzing a manufacturing process, providing a tool for the production of high-quality parts at low cost. It can eliminate several processing problems before a manufacturing process begins or before part design is finalized. It estimates optimum process parameters for a manufacturing process to get a high-quality product. It can save a significant amount of time and money for product fabrication. In an RTM process, a simulation model can be used to predict the flow pattern and evaluate any dry areas in the product. It can determine optimum process parameters such as injection pressure, resin viscosity, and gate loca- tion to get complete impregnation of the reinforcements with the resin. The . pre-cut, pre-weighed pieces of sheet composite materials, called blanks, for processing. TABLE 6.6 Part Cycle Time for Various Manufacturing Processes Manufacturing Process Part Cycle Time (s) Compression molding. pre-cut, pre-weighed pieces of sheet composite materials, called blanks, for processing. TABLE 6.6 Part Cycle Time for Various Manufacturing Processes Manufacturing Process Part Cycle Time (s) Compression molding. manufacturing processes. 7.2 The Importance of Models in Composites Manufacturing A process model is very helpful in analyzing a manufacturing process, providing a tool for the production of high-quality