Rigidization via Internal Resistive Heating

Rigidization of inflatable space structures via internal resistive heating requires carbon fiber reinforced material to consolidate and cure on-command. In terms of the spacecraft’s life, the rigidization process transforms a structurally weak “balloon” into a robust, stable design. Internal resistive heating provides an active approach for inducing permanent shapeholding and structural stiffening and has been addressed extensively in Chapter 2. The use of internal resistive heating with feedback temperature control is applied to a novel, thermoset resin-coated carbon fiber composite. The material hardening initiated by Joule heating will be evaluated as a function of several curing parameters and compared to uncured material. A method for quantifying the change in material properties is experimentally measured through an instrumented test apparatus. The goal for this study is aimed to correlate the change in mechanical properties and resin curing to factors such as the curing temperature, curing time, and heating rate. Furthermore, the amount of increase in stiffness per unit of applied energy is also considered since internal resistive heating is traditionally an energyexpensive method. This chapter addresses the issues and techniques associated with quantifying change in stiffness as a result of the curing process. First, the materials of interest (both the thermoset resin and reinforcing carbon fiber) are discussed. The primary experimental setups for measuring material stiffness are then described. Results of these tests are then presented and their significance is discussed.