Thermal-Acoustic Fatigue of a Multilayer Thermal Protection System in Combined Extreme Environments

Abstract

In order to ensure integrity of thermal protection system (TPS) structure for hypersonic vehicles exposed to severe operating environments, a study is undertaken to investigate the response and thermal-acoustic fatigue damage of a representative multilayer TPS structure under combined thermal and acoustic loads. An unsteady-state flight of a hypersonic vehicle is composed of a series of steady-state snapshots, and for each snapshot an acoustic load is imposed to a static steady-state TPS structure. A multistep thermalacoustic fatigue damage intensity analysis procedure is given and consists of a heat transfer analysis, a nonlinear thermoelastic analysis, and a random response analysis under a combined loading environment and the fatigue damage intensity has been evaluated with two fatigue analysis techniques. The effects of thermally induced deterministic stress and nondeterministic dynamic stress due to the acoustic loading have been considered in the damage intensity estimation with a maximum stress fatigue model. The results show that the given thermal-acoustic fatigue intensity estimation procedure is a viable approach for life prediction of TPS structures under a typical mission cycle with combined loadings characterized by largely different time-scales. A discussion of the effects of the thermal load, the acoustic load, and fatigue analysis methodology on the fatigue damage intensity has been provided.

A Review of Fatigue Failure and Life Estimation Models: From Classical Methods to Innovative Approaches

“…In cases involving brittle materials, Goodman's model coupled with the maximum principal stress proves to be more suitable. In the realm of uniaxial fatigue modelling, structures' fatigue life is commonly predicted by accounting for non-zero mean stress under combined thermal acoustic loadings [97]. When metal structures face such loading conditions, they encounter multiaxial fatigue issues, thus, complicating the cumulative assessment by introducing significant errors in the outcome of the uniaxial model [98].…”

Nonlinear dynamic response of a sandwich structure with flexible core in thermal environments

“…Its origin is placed at the left corner on the reference surface. In the present work, the materials of the plain-woven fibre reinforced face-sheets and core are both homogenous and orthotropic, and material properties are nearly temperature-independent due to their manufacturing procedure at elevated temperature [1–3]. The face-sheets are perfectly bonded on the top and bottom surface of the flexible thick core.…”

“…In order to protect substructures of a hypersonic vehicle, a sandwich panel with plain-woven high-alumina fiber reinforced composite facesheets bonded to flexible silica aerogel core is used as a critical component for thermal protection system (TPS). Silica aerogel has low thermal conductivity because of its ultra fine skeleton particles and nano-porous microstructure [1–4]. Thus it shows excellent thermal insulation properties due to characteristic of its microstructure.…”

Utilization of modal stress approach in random-vibration fatigue evaluation

“…The fatigue failure induced by random dynamic loads is termed as random vibration fatigue, or random fatigue (also called as stochastic fatigue in some literature), which has aroused considerable research interests recently. 4–8…”

“…The fatigue failure induced by random dynamic loads is termed as random vibration fatigue, or random fatigue (also called as stochastic fatigue in some literature), which has aroused considerable research interests recently. [4][5][6][7][8] Different approaches have been reported in the open literature for predicting fatigue damage and service life in engineering structures subjected to random loads, which can be broadly divided into two categories: cumulative damage based theories 9 and fracture mechanics based theories. 10 At the present time, cumulative damage based approaches are still playing a key role in evaluating fatigue life of aerospace structures and components subjected to random-vibration and/or acoustic loads, because of its conceptual simplicity and well applicability to both metals and composite materials.…”