Ms. Servane Altman, an AFRL wind tunnel project engineer from the University of Dayton Research Institute (UDRI), summarizes the effort: “We tested at UDRI. They tested the RP materials using the American Society for Testing and Materials standard. We had coupons made in the different shapes required for testing different properties, and UDRI collected their tensile, bearing, flexion, glass transition, and melting temperature data.” Test results identified two stereolithographic materials and one laser-sintered material meeting AFRL’s specific wind tunnel requirements.

In addition to providing valuable RP material property information, this experimental research effort saved significant time and money over AFRL’s alternative: developing RP materials inhouse. Researchers will need to repeat this effort frequently to leverage the RP industry’s continuous advancements. RP remains a relatively young technology and has plenty of room for improvement. For example, RP machines currently produce models that are limited in size. To construct larger models, researchers must first fabricate sections and then piece them together. Another area warranting attention involves finding better ways to embed sensors in RP models (see Figure 2). Finally, researchers must explore manufacturing improvements, because the layered construction of RP models renders them less accurate than traditional models.

Until these challenges can be addressed, traditional model building techniques will remain necessary to certain applications. As Mr. Dale indicates, “There is still a need for conventional model machining techniques, because RP has not progressed (and maybe never will) to the point where you have the material strength and temperature capabilities required for many of the wind tunnel testing environments. And while RP may never fully replace existing model machining techniques for these environments, we will take advantage of new RP materials and processes where possible to help reduce the technology assessment timeline.” AFRL intends to stay at the forefront of this process by collaborating with industry to support the warfighter.

Ms. Melissa Withrow (Azimuth Corporation), formerly of the Air Force Research Laboratory’s Air Vehicles Directorate, wrote this article. For more information, contact TECH CONNECT at (800) 203-6451 or place a request at http://www.afrl.af.mil/techconn_index.asp. Reference document VA-H-06-01.