Single Lap Shear Bolted Test Plans

This test plan will give a general overview on the test plan required to complete this experiment.

Background Information:

Several components of the seat will use a fastener to conjoin two composite materials together. An alternative option to the use of adhesives is the use of a fastener. The use of a single lap shear (bolted) test plan is to simulate the strength of the material as 2 composites are joined together using a fastener. An instance where the bulkhead interfaces with the seat. Since both are made up of composites, this document will test their strength (tensile) but in smaller test specimens. The red rectangle is an approximate location to where the bulkhead and seat will interface by the use of a fastener.

Open

Test Specimen Requirements:

• Condition the specimens if required

• Cleaning: ensure that specimen is cleaned and that when placing lubricant it is placed on the nut threads instead of the fastener threads. In addition, any spillage of oil onto the testing equipment (grips) or surface of the specimen must be cleaned prior the experiment

• Specimen Geometry: the ratio of width to to whole diameter should at least be a factor of 6. Unless we are altering this as a test constraint for the test specimens. In addition, the ratio of hole diameter to thickness ratio should range from 1.5-3. When using a countersunk bolt (flush bolt), the ratio of head depth to thickness ratio should be 0 - 0.7.

• The drilling of the two holes for both test specimens should be done beforehand

The shape of a single test coupon should be similar to the image below.

Open

For this test specimen the length was 5.5in, width of 1.5in, thickness of 0.125 - 0.208, a hole diameter of 0.250, and a hole to edge distance of 0.75in.

Equipment Needed:

• Calipers

• Universal testing machine (UTM)

The testing machine needs a stationary and a moveable head. The drive mechanism should be capable of moving the head and adjusted by controlling the velocity with respect to the stationary head. In addition, a load indicator should be present calculating the total load utilized while the test is running.

• Metal Fasteners

• Self aligning grips

• Torque wrench

Needed to torque fasteners to a specific value to avoid damaging the specimen. In addition, the torque wrench should be accurate enough to determine the applied torque to +/- 10% of the actual value.

• Bearing Strain Indicator (able to measure longitudinal hole deformation simultaneously on opposite sides of the specimen

Preparation of Specimens:

• Ensure preferred joint geometry is manufactured and shaped like test coupons

• Condition the specimen if required

• At least 3-5 specimens should be used per test condition

• Tighten the fastener to required value using a torque wrench and record the value

Procedures for Testing

• Measure the specimen dimensions. Measure specimen width, thickness, hole diameter, distance from hole edge to specimen end, measure fastener/pin diameter.

• Place the specimen onto the the grips of the UTM and make sure they are secure and tight. Place specimens on eye level so that specimen is vertical to the two grips and not at an angle. It is essential that we are not applying additional force to the specimen such as a bending force prior to the test as this will invalidate the results. The image below shows how the specimen is to be held by the grips and a type of failure that would occur.

• Attach the bearing strain indicator to each edge of the specimen to which this will provide an average displacement across loaded hole. Also attach recording instrumentation to the bearing strain indicator.

The top image shows where the bearing strain indicator is to be placed on the specimen

Note: The use of this device and checking for the availability should be researched before onsite testing.

• Apply a tensile force onto the specimen until failure or until the loading has dropped from 30% of its max value then test is terminated.

Note: If the ultimate bearing strain rate is unable to be found. Initial test trials should be done before testing of actual test coupons.

Data Recording:

• record load vs bearing strain

• record load vs hole displacement

record both at continuous or frequent regular intervals.

• record failure load, bearing strain, max load (Only if the target is the specimen to fail)

• record failure load, bearing strain, and type of failure (Only if target is to find a type of failure mode)

Image below is an image of what this experiment should look like. Noting that the two composites are joined by a fastener instead of an adhesive.

Loading Configurations:

• Single lap shear at max should be at least (80kg + mass of seat)*5*9.81

• Mass of front seat is around 6.4kg

• Essentially pulling the two pieces of composite away from each other to simulate what would happen if bulkhead and seat were pulled apart