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Predicting failure mechanism of syntactic foam core sandwiches with multi-layered core

Student thesis: Doctoral Thesis

This thesis presents the results of optimizing loading capacity of the sandwich panel by proposing a functionally graded sandwich panels and predicting the detailed failure mechanism of such panels. This study implemented the finite element based Extended This thesis presents the results of optimizing loading capacity of the sandwich panel by proposing a functionally graded sandwich panels and predicting the detailed failure mechanism of such panels. This study implemented the finite element based Extended Cohesive Damage Model (ECDM) to study the detailed failure mechanism of functionally graded sandwich panel.

This research first time explored an in-depth investigation on the failure mechanism of syntactic foam sandwiches with a multi-layered core. This sandwich consists of laminated fibre sheets on the top and bottom individually, and a syntactic foam core with multiple graded layers between two laminated sheets. The failure mechanism of this kind of syntactic foam sandwich panels were studied through numerical modelling under quasi static three-point bending. The prediction showed perfect agreements with experimental work on investigating the sandwiches with homogeneous core and the core with four functionally graded layers. This investigation did not only found that the failure mode of a sandwich panel with the multi-layered core is shear failure dominated delamination but also found an excellent mechanical performance when the core has multiple graded layers in the investigated sandwiches compared to the case of the homogenous core. The delamination was along with the path close to the interface between the core and the bottom sheet. The correlation between loading capacity and the number of graded layers in the core of the investigated syntactic foam sandwiches is introduced for the first time. The ECDM predicted loading capacity of the investigated sandwich panel with an 8- layered core is increased ultimately by 61% compared to the case with the homogenous core.

The geometric ratio, depth to span, of sandwich panel affects failure behaviour. Hence, it is the first time that this investigation explored geometrical ratio effects on the failure mechanism of functionally graded sandwiches with multi-layered cores. The FGSP showed different failure modes when their geometrical ratio between the depth and the span varies. Furthermore, this research also introduced the correlation between the failure load and the geometrical ratio of the FGSP with a multi layered in the core.

The outcomes of this research contribute to academic knowledge, and industrial applications are summarized as follows:

-It is the first time that this work explored the detailed failure mechanism of functionally graded syntactic foam core sandwich panel having more than four layers in the core using ECDM;
-It introduced the correlation between failure load and the number of layers; ⮚ Likewise, geometric ratio effects on the failure mechanism of functionally graded sandwich panels are studied;
-Finally, it also introduced the correlation between failure load and the geometric ratio;
-Academically, these novel contributions can be used for future research as a benchmark. Likewise, this correlation can be used to predict the failure mechanism of the intermediate number of layered cores to gain a general overview of the initial design of FGSP;
-These findings can be used to carry out further researches and to manufacture sandwich panels for various engineering applications with different geometrical depth-span ratios and variable layered sandwich cores;
-This investigation also showed that the ECDM is a robust tool for predicting failure mechanism of syntactic foam sandwiches.
Original languageEnglish
Awarding Institution
Supervisors/Advisors
Award dateOct 2020

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