CompositesWorld
Issue link: https://cw.epubxp.com/i/697353
CompositesWorld.com 23 NEWS N E W S N S N E W S E N W S W Thermoplastic Composite Wing by the Spanish Industry and Innovation Ministry and also part of CENIT, produced more panels as well as more complex struc- tures, and investigated methods for co-consolidation. Te Green Regional Aircraft (GRA) project, concluded in 2015, and the most recently completed Clean Sky ISINTHER (Industrialization Set up for In Situ Consolidation Process in Termoplastics) project, have enabled FIDAMC to develop an in-situ manufacturing process, says Rodriguez. Now, under the Clean Sky 2 OUTCOME project, the previous work will be moved toward maturity. OUTCOME partners include Aernnova (Miñano, Spain) and Spanish aero- nautical centers Tecnalia (Derio), CATEC (Seville) and CTA (Aero- nautical Technologies Centre, Miñano). ADS is the OUTCOME work activities leader. Although automated methods for laying thermoplastic prepreg are certainly proven technology, they are not yet ready for large primary structure, so a lot is at stake. "Current thermoplastic methods require forming equipment, presses — often an auto- clave," Rodriguez explains, referring to the practice by others of briefy autoclaving thermoplastic parts to boost consolidation and reduce porosity to <2%, which "requires high capital and energy costs, with a typical focus on smaller parts. We are developing a completely out-of-autoclave process, while maintaining good properties, for large parts." Te opportunity for one-step produc- tion, he says, involves gas torch, infrared or laser heating of the material, and integration of structure by co-consolidation — that is, melt-fusing the skin and stringers in one step. In the ISINTHER project, a co-consolidated thermoplastic demonstrator panel was produced in three distinct stages: 1) Stifener laminate blank layup, with plies consolidated by the MTorres automated fber placement (AFP) laser- heated head; 2) Thermoforming of the stifeners using a press; and 3) Flat and curved skin panel layup over the formed stringer feet, with panel manufacturing and stringer integration in one step (in-situ consolidation). Necessary to the project was the MTorres AFP head, installed six years ago at the FIDAMC facility on a gantry machine, equipped to melt, deposit and freeze the unidirectional thermoplastic slit tape on a fat or mandrel tool. Its heat source is a 500W Nd-YAG (neodymium-doped yttrium aluminum garnet), variable optic diode laser, capable of continuous and consistent heating of the prepreg to 400°C, the temperature necessary to melt high-perfor- mance thermoplastics. A scanner optimally distributes the laser energy between the incoming tape and the substrate. A conform- able consolidation roller applies sufcient force to the heated prepreg to achieve co-melting and consolidation. Te MTorres AFP head employs the company's patented rotary cut-and-add on the fy, for rapid laydown without stopping for cuts. When the machine was installed, it had a single roller to apply pressure in the melting zone, but a second roller was added for additional consolidation during the cooling or freezing phase, when the material crystallizes. Rodriguez recalls that several roller materials were tried. Te best solution was two rubber rollers. Automated laydown … and an added laser Automated equipment used for the previous, and current, thermoplastic wing projects at FIDAMC is provided by MTorres (Torres de Elorz, Spain) and is equipped with two lasers. The head's process-monitoring instru- ments, which can be observed on the lower left, include recording devices for monitoring laydown speed. Source | FIDAMC Equipped for co-consolidation The MTorres head also is equipped with two temperature-resistant rubber rollers for in-situ consolidation of the thermoplastic prepreg. Source | FIDAMC He adds, "Te critical issue during consolidation is to maintain the temperature long enough to get proper heat transfer through the entire laminate." Tat led to several machine modifcations over the course of the previous projects. Te fnal change was the addition of a second laser, between the two rollers, which enabled modifcation of the cooling rate and, consequently, the degree of crystallization, to achieve the best material properties. Te head also is equipped for process monitoring: it features an infrared camera and a pyrometer to record application tempera- tures and track thermal history during processing. It also records laydown speeds. For the ISINTHER project, stringers were made frst by laying up, on a fat metal tool, 6.2-mm wide AS4/APC2 carbon fber/poly- etheretherketone (PEEK) thermoplastic unidirectional slit tapes supplied by Cytec Solvay (Brussels, Belgium). Te layup sequence (0°/90°/+45°/-45°), created a blank with a nominal thickness of