The Testing of Composite Coupons
The testing of composite coupons is typically accomplished using large (better averaging), high resistance (to avoid grid self-heating) strain gages. Soldering to attach the leadwires to the bonded gage could cause local damage to the coupon or the gage due to excessive heat, since composites are typically poor heat sinks. The flexible, but rugged, polyimide backing of Micro-Measurements CEA-Series gages makes them a good choice for this application, and adding Option P2 (preattached leadwires) to the gage selection – such as the CEA-XX-250UW-350/P2 – is recommended.
Use an adhesive that can be cured at room temperature and has high elongation capability, such as M-Bond AE-10 or GA-2. Particularly if the coupons require humidity conditioning, these adhesives are better choices than the popular M-Bond 200 because they are more moisture-resistant.