Structures and Materials for Extreme Environments (SMEE)

High performance composite materials are being incorporated into many aerospace structures, where their specific stiffnesses and strengths are advantageous. It is critical that these materials are proven in the extreme enviroments to which they will be subjected. Furthermore, it is vital that modeling techniques keep pace or exceed advances in the materials, so that engineering analysis can drive the design of structures that are enabled by these materials.

A critical area currently being investigated at the University of Michigan is analysis of adhesively bonded joints. Bonded joints offer improved load distributoins over the fasteners that they are replacing. However, techniques for designing these joints are immature, particularly in the arena of extreme environments. The constitutive and structural responses are highly non-linear, and require special attention in order to provide a converged predictive solution.

Current efforts have focused on the Discrete Cohesive Zone Model (DCZM), a technique, developed in the Aerospace Engineering Department. Using this technique, researchers have had significant success in predictive modeling of joint behavior at the coupon level over a broad range of temperatures. Furthermore, recent advances have shown that the technique generalizes to the structural level, where good correlatoin has been achieved with experimental results. The current effort is at the leading edge of donded joint analysis, and is expected to continue to provide industry leading solutions for analysis of joint failure and composite delamination.

Stiffened composite specimen subjected to compression and buckling. Adhesive failure is predicted at the termination of the stiffener.