CompositesWorld
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NEWS CompositesWorld.com 43 e appeal of thermoplastic tapes was not hard to see. Being UD, they could be applied to meet almost any mechanical force. ey were melt-processible and could be consolidated easily and quickly via stampforming (that is, out of the autoclave) or compression molding (Fig. 1, above and Fig. 2, p. 44). ey offered toughness properties that could not be matched by thermosets, and, unlike thermoset prepregs, they could be stored indefinitely at room temperature. However, as defense spending waned in the 1990s, particularly in the United States, so did interest in and application of ther- moplastic tapes. Suppliers such as DuPont, Phillips Petroleum, Exxon, BASF and Imperial Chemical Indus- tries (ICI), which had invested heavily in thermoplastics tape development, got out of the business. is is not to say that ther- moplastics tape development ceased, but it slowed significantly in a time when develop- ment of thermoset composites, in general, including thermoset tapes, was accelerating. is led eventually to the application of the latter in large aerospace structures in the Boeing 787, Airbus A350 XWB and other commercial aircraft. Fast forward to 2018. e commercial aerospace world is looking to the future, and the next major aircraft program expected to consume large quantities of composite materials, in all likeli- hood, will be Boeing's new Middle of the Market (MOM) aircraft, designed to replace its 757. Also on the horizon are redesigns of the Boeing 737 and Airbus A320, the narrowbody workhorses that are the backbone of the global commercial aerospace industry. e material and process economics that justified use of composites on the 787 and the A350 XWB are not the same as those for the MOM, 737 and A320. e biggest difference is rate. e 737 and the A320, in particular, are as close as the commercial aerospace sector gets right now to a commodity, which means the faster they can be made, the more profitable they are for OEMs. And with a targeted rate of 60 per month or more for the 737 and A320 (and whatever replaces them), that's two planes a day, every day. ermoset composites, cured in an autoclave, are currently not a good fit for such a high-volume environment. And that's where thermoplastic tapes come back into the picture; they offer cycle time, materials storage, toughness, and recyclability advan- tages that cannot be matched by thermosets. ey already are used today to make smaller parts and substructures, including clips and brackets to connect fuselage skins to stringers and frames (see Learn More, p. 48). And they are employed on a number of structures for smaller aircraft, including tail planes, wings and other parts for business jets (also see Learn More). Further, the oil and gas industry has embraced thermoplastics because of their toughness and corrosion resistance, and the automotive industry is drawn to their adaptability to high-volume manufac- turing and recyclability. e biggest question facing those who would use thermoplastics in commercial airframes is, Are they viable in highly loaded aircraft structures? Scott Unger, chief technology officer at thermoplastics specialist TenCate Advanced Composites USA Inc. (Morgan Hill, CA, US), who has worked with thermoplastics for more than 30 years, says, "e growth of thermoplastics is at an inflexion point. e ability to get out of the autoclave, reduce costs and ease parts assembly are big drivers." The current state of the material and process art ermoplastic tapes, for the purposes of this article, consist of unidirectionally aligned carbon fiber tows in widths of up to 12 inches/305 mm, prepregged with a thermoplastic resin (see opening photo, p. 42). e resins most commonly used in aero- space and other high-performance applications are the following FIG. 1 CFRTP: From brackets to big parts This clip, compression molded from a woven carbon fiber thermoplastic material supplied by TenCate, is emblematic of the potential the material has in aerospace applications. Efforts are underway now to migrate reinforced thermo- plastics into use on large, heavily loaded aerostructures. Source | TenCate Advanced Composites Thermoplastic tapes offer cycle time and many other advantages that cannot be matched by thermosets. Thermoplastic Composites