Large strain flexural testing of thin composite laminates

Carbon fiber composites are of significant interest for use in deployable space structures. Elastically folded thin laminates can be utilized as hinge mechanisms in structural systems such as solar arrays, reflectors, and instrument booms, allowing for compact packaging during launch to orbit. While the initiative to utilize composite laminates in deployable structures has increased it also has faced difficulties in design and analysis of these poorly understood materials. Data from standardized ASTM test methods fails to characterize nonlinear constitutive behavior over the full large strain range common to deployable structures. Flexural behavior is characterized by the moment vs. curvature response therefore requiring a bending test. A special test fixture is developed to allow flexural testing of thin plates at large strains. Reaching large strains during the test provides an opportunity to investigate the large strain linear and nonlinear elastic constitutive behavior of glass and carbon fibers respectively.