C3_blade_SOO_4_3-2019.pdf

Distribution A – Public Release Distribution Unlimited

AEDC – 16S C3 Blade Inspection and testing Statement of Objectives (SOO)

Project: 14576 Agency: Department of the Air Force

Office: Air Force Test Command Location: AEDC – Arnold Engineering Development Complex

1. Facility Background

The PWT 16-ft Supersonic Tunnel (16S) is a continuous-flow, closed-circuit wind tunnel.

The main compressor of Tunnel 16S consists of four axial-flow compressors (referred to as C2, C3, C4, and C5). This SOO regards the blades in the C3 compressor.

The blades are made of an AMS 4143 2219-T6 aluminum spar with fiberglass shell. The shell is made with 7581 E-glass, soft A1100, and Hexcel F-187 resin. The spar wrap is made with 1543 E-glass, soft A1100, and Hexcel F-178 resin. The shell is bonded to the spar wrap with FM-34 adhesive.

The blades currently weigh approximately 60 lbs., 4ft tall, and about 2ft wide each. The blades operate at 600 revolutions per minute (RPM) and are expected to be exposed to the following temperatures during their 10,000 operating-hour lifetimes:

- 1000 hours at 420 deg F

- 9000 hours at 375 deg F

A simple test was conducted by pulling the blade in tension to failure in 1997 at Hamilton Standard. This results of this test were inconsistent, with blade failures occurring at anywhere from 40 psi to 2371psi. The report states the bonding process was insufficient and a corrective manufacturing process was implemented. However, it is currently unknown how much the insufficient bonding or the attempted corrections have impacted the blades’ service life.

In 2013 the AF conducted an inspection and some structural testing on C3 blades at WPAFB.

Although, at that time the people conducting the inspection were not aware of the possibility of having regions of the blade with resin rich areas in the shell due to a manufacturing issue. Therefore, when that inspection was performed, that type of defect was not considered.

2. Objectives This Statement of Objectives (SOO) identifies the wide-ranging, basic, and top-level objectives of the 16S C3 blade inspection, testing, and developing repair methods. It will be used as a focusing tool for both the Government and offerors. This SOO addresses the AEDC 16S C3 Blade Inspection and testing Requirements.

The following is an outline of the objectives of 16S C3 Blade inspection, testing and development repair methods. These are the minimum objectives that must be met for this effort to be considered a success.

a. Sample blade piece testing

i. Deliver a non-destructive inspection utilizing Pulse Echo Ultrasonic C-scan for both sides of the sample piece in the spar area.

ii. Perform through thickness flatwise tensile testing per ASTM D7291 using specimens taken (4 min) at areas selected based on the results of the UT scan, inspect failure surfaces and any chemical testing of the bond-line which might be useful to determine the bond strength.

iii. Burn off testing of shell segments per ASTM D792, D3171, D2734 to look at lay-up, and laminate quality including void content

iv. Any further testing of the bond area (destructive or NDI) which may help further characterize the bond strength approved by the Government.

v. Submit a Failure analysis and data summary report including documentation of test failure modes (optically) and correlating test results to inspection findings.

Frequency: Once Due: 45 days following project award

b. Optional Further Inspection and Testing

These items may be requested by the AF if cost and the outcome of sample blades piece testing and inspection are deemed acceptable. Details of these optional task are below.

Option 1 – Single Full blade inspection and testing

Proceed to this option if the results from the sample blade show promise for correlation of bond strength and the result of the inspection.

a. Deliver a Pulse Echo Ultrasonic C-scan inspection of the entire spar area of the blade on both sides.

b. Flatwise tensile testing per ASTM D7291 of areas adjacent to known disbonds and in areas which Part 1 would indicate poor bond quality (8 minimum)

Due: 45 days following notice to proceed

Option 2 – Multiple blade inspection

a) Deliver a Pulse Echo Ultrasonic C-scan inspection of 2 additional blades with known disbonds and 1 blade which has not been installed in the compressor.

b) Perform flatwise tensile tests per ASTM D7291 on disbonded blades (6 minimum per blade)

Due: TBD before the notice of proceeding

Option 3 – Development of repair method for the blade

This task may be requested by the AF if a repair method is needed regardless of the results from the above sections.

a. Design a repair for one specific shell-to-wrap disbonded blade selected by the NIAR/AEDC team.

b. Design a repair for one specific wrap-to-spar disbonded blade selected by the NIAR/AEDC team.

c. Investigate the suitability of performing a resin injection repair.

d. Transfer the method by which the repairs were designed to AEDC so that AEDC may design a blade specific repair for other C3 blades.

e. Perform the scarf repairs for the blades chosen in a and b.

f. Perform post-repair inspection on the blades chosen in a and b.

Option 4 – Repair fatigue testing

This task will depend on the results of option 3.

a. Coupon level fatigue testing of sections of the blades repaired in Option 3.

b. Peel strength, flatwise tension and shear strength testing of bond line areas taken from the repaired blades from option 3.

Option 5 – Destructive testing

This task will depend on the results of options above and is destructive testing of an AEDC repaired blade

a. Preform flatwise tensile tests on repaired areas of blade chosen by AEDC as well as non-repair areas, min 6 tests.

b. If the blades shows poor bond quality in the repaired area section the blade or preform other destructive testing as required to determine issues with the repair.