SATPC0032767 Tab 04 4 SOW..pdf

TDEA Welding study: SLS and DCB tests

Single lap shear (SLS) and double cantilever beam (DCB) tests shall be performed on materials welded with ultrasonic, induction and conduction methods. Each welding method outlined in the table below includes 5 materials: AS4/PPS, AS4/PEEK, AS4/PEI, T700-LM-PAEK and M30S/PEKK (thin ply)

Weld Method Test Coupons Per Material to be tested at

NIAR

Total Coupons tested at NIAR (x5 materials)

Ultrasonics SLS 6 30

DCB 3 15

Induction SLS 6 30

DCB 3 12*

Conduction SLS 6 30

DCB 3 15

Resistance SLS 6 30

DCB 3 15

*M30S/PEKK (thin ply) will not be tested

General Specifications The objective of these tests is to support TDEA’s study of thermoplastic composite material weldability via mechanical joint performance evaluation. While ASTM standards are used to guide the tests, the overall effort is not simply standard engineering tests. Developmental welding methods and materials are included, several non-standard procedures are required, and therefore unexpected results outside the scope of the ASTM standards may occur and so special care and attention are needed to ensure success of the test program.

Requirements A NASA representative shall be on-site during the initial testing of DCB and SLS specimens to witness the procedures, results, and approve any changes to the following requirements or ASTM standard procedures.

The test engineer shall record observations during testing, for example: evidence of slipping in grips, audible emissions that occur prior to failure (including approximate displacement), and other evidence that may help explain the structural behavior and damage process.

SLS Test Specifications

120 SLS specimens shall be tested following ASTM D5868 with some modifications as described below.

• Load introduction: the 1 in. x 1 in. grip region on the two ends of the specimens shall have bonded tabs with thickness equal to the substrates +/-0.01 in. Hydraulic and mechanical wedge gripping of the test specimens are permissible as needed. The grip pressure should be such that the gripped surfaces of the tested specimens show even and uniform indentation from the grips without evidence of slipping. When using hydraulic grips, the test engineer shall record the grip type and model number, gripping pressure and select a pressure that does not introduce damage to the specimen. If slippage is noticed, the observation shall be noted in the test results and the grip pressure in subsequent tests shall be increased.

• Load frame requirements: Tests will be conducted at ambient conditions. The load frame required for introducing load into the sample shall be a servo-hydraulically activated load frame. The load cell (load measuring transducer) shall be ensured to be in proper calibration. The load cell shall be selected such that the cell utilizes greater than 30% of the capacity to ensure that the measurement is free of noise. Load frame and specimen alignment is critical to generate uniform tensile loading of the specimens that is repeatable. To ensure minimal bending in the specimen and consistent alignment of specimens in the load frame, the following load frame and specimen alignment requirements must be met:

o Load frame alignment shall be in accordance with ASTM E1012 to a Class 5 or better specification. Alignment data shall be provided to NASA prior to testing for review. Testing shall not proceed until NASA approves the load frame alignment data.

o The specimen shall be placed in the grips such that the centerline of the specimen in the specimen loading direction coincides with the geometric center of the crosshead.

o The specimen shall be gripped over the full tab region so that the free length between the grips is 5 in.

• Pre-test measurements: The following measurements shall be reported for each specimen to at least +/- 0.001 in. Where measurements are specified at multiple locations, the locations of the measurements shall be provided to +/- 0.03 in.

o Leg thickness at three locations (for each leg) o Leg width between grip and overlap regions o Leg length o Overlap thickness at three locations o Overlap width at three locations o Overlap length at two locations o Tab region thickness (for each leg) o Leg deviation from parallel as shown in the sketch below (three directions) o Overlap flatness (height gauge, feeler gauge, CMM, or other 3D scan are acceptable)

• Strain gages: All specimens shall be gaged with four (4) load introduction gages, (CEA-

06-187UW-350, CEA-06-250UW-350 or equivalent) mounted in back-to-back pairs at 1) centered on the overlap and 2) centered on a leg between the overlap and grip region.

Odd numbered gages, shall be placed on the front surface, and even number gages shall be placed on the back surface. Gage model and calibration information shall be provided in the test data report.

• Extensometers: Two (2), two-inch extensometers with knife edges, one on each edge of the specimen, centered longitudinally on the overlap (to +/- 0.03 in.) will be attached to the specimen for measuring specimen extension. The extensometers shall have ~0.1-inch full-scale displacement value. Extensometer model and calibration information shall be provided in the test data report.

• Loading procedure: All specimens shall be loaded and unloaded under stroke control.

The displacement rate shall be set to 0.02 inches per minute. This rate may be adjusted at the discretion of the test team based on specimen response so that the total loading duration is between 2 and 5 minutes from initial loading to specimen failure.

• Sampling rate: Data for all instrumentation shall be obtained during loading and unloading. Data sampling rate shall be 10 samples per second for strain gages, load, stroke, command (if available on system), and the extensometers.

• Test photos: Photos of the test configuration/ set up shall be taken that include test part identification in the photo name or is clear within the picture. After testing, each specimen shall be photographed to document the failure surfaces.

DCB Test Specifications 57 DCB specimens will be tested following ASTM D5528 with some modifications as described below.

• Load introduction: bonded hinges or blocks are acceptable per D5528. However, if debonding is noticed, mechanical load introduction (“the Boeing method”) using pins inserted through a hole drilled through the specimen width at the insert shall be used for the remaining specimens.

• Load frame requirements: Tests will be conducted at ambient conditions. The load frame required for introducing load into the sample shall be a servo-hydraulically activated load frame. The load cell (load measuring transducer) shall be ensured to be in proper calibration. The load cell shall be selected such that the cell utilizes greater than 30% of the capacity to ensure that the measurement is free of noise.

• Pre-test measurements: The following measurements shall be reported for each specimen to at least +/- 0.001 in. Where measurements are specified at multiple locations, the locations of the measurements shall be provided to +/- 0.03 in.

o Thickness at six locations o Width at three locations o Flatness (height gauge, feeler gauge, CMM, or other 3D scan are acceptable)

• Test photos:

o Photos of the test configuration/ set up shall be taken that include test part identification in the photo name or is clear within the picture.

o Photos of the crack propagation as viewed from the edge shall be recorded and provided with synchronization to load.

o After testing, the specimens shall be broken apart and each specimen shall be photographed to document the failure surfaces.

Data shall be provided in an excel spreadsheet.

Specimens shall be returned to the POC.