The U.S. Air Force and the Ohio composite team developed new processes for the S-shaped aircraft structure.
Prior to resin injection, an 11 foot long imported pipe prefabrication was shown as part of the Air Force Research Laboratory (AFRL) program to reduce the cost of drones, such as Kratos xq-58 Valkyrie (as shown in the figure), by Kratos Defense & amp; Security solutions designs and manufactures the air force low cost attack demonstrator program for the AFRL's low cost aircraft technology portfolio.
Part of the air force's 2030 science and technology strategy includes large-scale deployment of low-cost UAV Systems to assist in future engagements. In order to achieve this goal, a new manufacturing strategy must be established to support rapid manufacturing of high-quality aviation components at a lower cost than traditional processes currently used.
The manufacturing and Industrial Technology Department of the Air Force Research Laboratory (AFRL) and the contractor teams of Dayton, a & P Technology (Cincinnati) and sintech LLC (Mexico) conducted the study. To quantify the advantages of using dry fiber braided preforms and vacuum assisted resin transfer molding (VARTM) instead of traditional prepreg hand lamination to create an 11 foot long S-shaped composite engine inlet.
The air intake of the aircraft engine can provide constant air to prevent the compressor of the engine from stalling. The entrance must produce as little resistance as possible. The minimum clearance in the air flow supply may cause major engine problems and serious efficiency losses. If the intake pipe is to provide enough air with minimum turbulence, the intake pipe must be clean.
The new manufacturing method of S-shaped air intake pipe replaces the manual layer prepreg on the multi-piece steel mandrel, and solidifies the autoclave through the automatic film covering process, so as to replace the dry fiber. The single shape memory polymer (SMP) mandrel with light weight is used to replace the multi sheet steel mandrel with heavy weight. Using VARTM and low cost epoxy resin, the dry woven carbon fiber was processed into composite structure and cured in oven.
The team completed the analysis of the braid architecture, the manufacturing of the SMP forming tool and the SMP mandrel used as the tool in the weaving process of the preform. Due to the complex geometry of the S-shaped inlet, it is necessary to carry out multiple iterations to optimize the machine settings of the woven mesh and minimize the wrinkling of the composite. A total of four intake pipes will be manufactured and the cost and production time of traditional parts compared to the new design.
"We believe that the introduction of reusable shape memory polymer mandrels, as well as automatic over weaving and oven based VARTM composite curing technology, will significantly reduce costs and shorten cycle time," said Craig neslen, technical program director, low-cost attriteable aircraft manufacturing, AFRL manufacturing and industrial technology department. "Quantifying manufacturing revenue and verifying structural integrity is critical to building a positive business case and convincing designers and manufacturers to incorporate new materials and processes into future low-cost engine inlet designs."
The final intake manifold will be delivered to the air force for further integration into AFRL's complementary airframe design and manufacturing program. Aerospace will conduct static ground tests of the integrated braided fuselage and intake structure.
"Although we have not yet defined all the effects of wear resistance on the design criteria and the final manufacturing materials and processes used, we do have a baseline of threshold requirements for strength and stiffness, which we will evaluate through a comprehensive airframe ground test," said Ray Fisher, aerospace engineering at the aerospace vehicle division.
Source: Air Force
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