In-situ measurement of viscoelastic effects in composite tape springs

Bi-stable composite tape springs present several volume efficient solutions for deployable structures in small satellites. Viscoelastic changes within the composite matrix of these materials caused by their long term storage and exposure to varying temperatures can negatively impact the ability to deploy the structure. This study investigates a method for developing an in situ sensor for structural health monitoring in space structures employing tape springs. A method is developed by employing a custom load cell to detect stress relaxation in a bent tape spring over a period of time and two tests of this method were conducted. Results from the first test reveal the correct trend for stress relaxation but with significant noise. The second test showed the cause of the noise to be material behavior changes due to temperature fluctuations. The results show the expected decreasing exponential trend in the strain data as stress relaxation occurs, proving the feasibility of the approach.