Deployment effects on stability of thin composite boom structures

Thin composite boom structures find large applications in erospace systems such as satellites, deep space probes, and solar sails. Booms are characterized by one-large dimension while the cross section is very thin and changes with the applications, affecting both weight and stiffness of the entire structure. In order to be stored and transported within a very small volume, booms are pressed down flatly and/or rolled up. Folding produces permanent stresses on the composite structure that act as a pre-load. In this work, we study the buckling behavior of thin composite structures considering the residual stress after deployment. The structural analysis was performed using the non-linear finite element method. A representative element of the boom was rolled up on a cylindrical mandrel and the stress due to the fact that the composite structure was changing shape were introduced as initial condition for the buckling analysis. The adopted model was a C cross- section with radius of 10 mm, thickness of 0.2 mm and 5 m length made by carbon fiber reinforced plastic (CFRP). Due to the small thickness, that causes a disagreement with the classical laminate theory, a modified laminate theory was considered in the model. Results show that the introduction of the stresses due to the folding reduce the critical load of the boom structure with respect to the case of considering geometrical imperfections in the model.