Smart Materials and Shape Memory Alloys for Aerospace Structures: Design, Actuation, and Fatigue Behavior

Abstract

Shape memory alloys (SMAs) offer extremely valuable specific work and small-scale integration of morphing and deployable aerospace structures, but more widespread integration in U.S. flight systems area has not occurred due to bandwidth, thermal electronic co-design, and fatigue reliability. This paper will build and test a computational experimental model of the SMA actuator design and life assessment to suit U.S operating conditions and qualification procedures. It is to (i) calibrate a constitutive model of NiTi and high temperature NiTiHf (ii) co-optimize actuation force, stroke as well as thermal bandwidth at electrical and heat-rejection constraints typical of U.S. UAV and aircraft subsystems, and (iii) quantify functional and structural fatigue in terms of thermomechanical protocols representing U.S. mission duty cycles. The methods involve the use of 1D/3D constitutive modeling, coupled electro-thermal transients of Joule heating and heat-sink sizing, and strain-/energy-based life models, that are tested against cyclic thermomechanical tests. The 68 high recoverable strain, 250-450 MPa recovery stress, and 1.53 actuation (ambient80 C) forced-convection heat sinking of a morphing UAV trailing-edge case-study comprises a recovery of 68 high, a recovery stress of 250-450 Mpa, and an actuation of 1.5-3.0 Fatigue tests and simulations predict that >10^5 cycles yield 0 complements strain amplitude of 0 -2 percent and 0 -4 percent prestrain, and life is dictated by the average stress, thermal peaks, and surface finish. Findings deliver design maps that are practical between prestrain, strain amplitude and heat sink UA against authority and life and give advice consistent with the U.S. qualification routes (e.g. thermal/vibration screening and health monitoring hook at subsystem level). We are able to arrive at a conclusion that co-designed thermal management and refined constitutive control allow certification eligible SMA actuators in aerospace in the U. S., whether in UAV morphing surfaces or mechanisms adjacent to engines, with HT-SMAs.