Background Information:
For single lap shear, since the seat is made of fully composite material we will be using smaller single lap shear joints with the same sandwich composition as the seat to test their durability and strength. The seats will be attached to the C and D bulkhead using an adhesive and thus, using a smaller size sample such as a test sample is perfect to check for adhesive strength. The image below is where the seat would interface with the bulkhead and where it is exactly located.
In addition the C and D bulkhead is adhered onto the chassis using an adhesive. Image below points at the chassis interfacing with the bulkhead.
Preparation:
This section will outline the needed steps to prepare the sample prior to the shear test as well as describe the setup of the test.
Test Specimen Requirements:
3-5 sample specimens
Shape similar to a test coupon, image below shows dimensions to what the composite should be manufactured to.
As seen in this image above, a single CF specimen should have a 1 inch width and a length of 4 inches
Equipment Needed:
Calipers
Universal testing machine (UTM)
Adhesive (We are currently looking at 3M DP420NS Black which is subject to change if we find something better)
Self aligning grips capable of grasping the specimen throughout the test
Preparation of Specimens:
Surface needs to be prepared before applying the adhesive, buffing out/sanding the surface for maximizing the adhesive contact
Adhesive cure: adhesive needs to be cured at a specific temp per manufacturer instruction
Joint Geometry: Shaped as test coupons, image above should be the sample dimension.
Conditioning: Allow parts to be bonded for at least an hour if they were cured at a higher temp than room temp. Follow adhesive instructions for cure time, plus an additional 10 min for reassurance
Testing: Ensure adhesive gaps for all specimens are consistent, and the grip separation is 75mm.
Variable | Quantity |
|---|---|
Loading Rate | 13mm/min |
Note: For metal to metal coupons the loading rate is 1.3mm/min
Procedures for Testing:
Condition the specimen if needed. Conditioning/Environmental Test Chamber if needed. Allow for proper cure time per manufacturer instruction.
Measure the specimen dimensions to ensure they are consistent
Place the specimen onto the loading fixture, (grips) and make sure they are secure and tight. Also, specimens need to be placed onto the UTM at eye level so that the specimen is at a vertical to the two grips and not an angle.
Apply a tensile force onto the specimen until failure and record the results.