A novel all-solid-state thin-film lithium-ion battery (LIB) is presented to address the trade-off issue between the specific capacity and stabilities in a conventional LIB. Different from the conventional one, this LIB device consists of two same LIB components located at the front and back surfaces of the substrate respectively. These two LIB components form parallel connection by using the conductive through vias distributed in the substrate. Compared with the conventional one, this LIB device doubles the areal specific capacity. More importantly, due to the stress-compensation effect, this device effectively suppresses the stress induced by its volume changes resulting from the lithiation/delithiation processes and thermal expansion. Consequently, this device shows good cycling and thermal stabilities even when working at an industrial-grade high temperature of 125 oC. To further improve the specific capacity without sacrificing the stabilities, a three-dimensional stacked LIB is successfully realized by using this LIB device as the cell, in which each cell is parallelly connected by using the above-mentioned conductive through vias. This three-dimensional stacked LIB is experimentally demonstrated to obtain high specific capacity (79.9 μAh·cm-2) and good stabilities (69.3% of retained capacity after 100 cycles at 125 oC) simultaneously.
ABSTRACT Fatigue crack growth of fibre reinforced metal laminates (FRMLs) under constant and variable amplitude loading was studied through analysis and experiments. The distribution of the bridging stress along the crackline in centre‐cracked tension (CCT) specimen of FRMLs was modelled numerically, and the main factors affecting the bridging stress were identified. A test method for determining the delamination growth rates in a modified double cracked lap shear (DCLS) specimen was presented. Two models, one being fatigue‐mechanism‐based and the other phenomenological, were developed for predicting the fatigue life under constant amplitude loading. The fatigue behaviour, including crack growth and delamination growth, of glass fibre reinforced aluminium laminates (GLARE) under constant amplitude loading following a single overload was investigated experimentally, and the mechanisms for the effect of a single overload on the crack growth rates and the delamination growth rates were identified. An equivalent closure model for predicting crack‐growth in FRMLs under variable amplitude loading and spectrum loading was presented. All the models presented in this paper were verified by applying to GLARE under constant amplitude loading and Mini‐transport aircraft wing structures (TWIST) load sequence. The predicted crack growth rates are in good agreement with test results.
NASA and the Chinese Aeronautics Establishment have participated in a Fatigue and Fracture Mechanics Cooperative Program giving attention to small-crack effects in high-strength Al alloys. Experimental and analytical investigations studied crack initiation and growth behavior of small cracks in both bare 7075-T6 and clad LC9cs Al alloys, with a view to the improvement of their fracture-mechanics analyses in the cases of surface crack and corner crack configurations. It is also expected that superior life-prediction methods will be developed in order to correlate and predict small crack and large crack growth with various load histories.
In order to understand micromechanisms offatigue crack growth in titanium aluminides, direct monitoring of the influence of the α2 and β phases on a growing crack was performed using an FEG SEM for Ti-23Al-9Nb-2Mo-1Zr-1.2Si (at.-%) and Ti-23Al-11Nb-0.9Si (at.-%) Ti3Al based alloys. Crack growth rates are observed to befaster across individual α2 laths than across β laths and/or along α2/β lath interfaces. It is found that fatigue cracks propagate incrementally through the α2 phase by decohesion of afavoured slip band rather than crossing it catastrophically in one cycle. The formation of intersecting slip bands can lead to a tortuous crack path and a decreased average crack growth rate in the α phase. When a crack meets the β phase, the most common phenomenon observed is crack deflection. The fatigue crack then extends continuously along α2/β interfaces under the effect of a mixed mode local stress intensity factor range. The basket weave microstructure achieves the maximum fatigue crack growth resistance from α2/β interfaces. Bridging and blunting can reduce fatigue crack growth rate remarkably. However, crack bridging happens only with larger β laths and blunting is mainly seen only for secondary cracks. The efficiency of bridging and blunting thus appears to depend on the ratio of load bearing capability of the β laths involved over the local effective ∆K range. Mechanisms operating during fatigue crack propagation are also compared with those observed during monotonic fracture.
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