Date

2016

Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Mechanical Engineering

First Adviser

Nied, Herman F.

Other advisers/committee members

Harlow, Gary; Webb, Edmund B.; Pearson, Raymond A.

Abstract

A layered foam composite panel system has higher moment of inertia, therefore increasing its bending stiffness. A low modulus backing material in the layered composite panel could provide energy absorption capability when a impact event occurs. These feature make the structure system very promising in many engineering field such as energy absorption, aerospace and automotive. Polymeric and textile reinforcements can be used to form a large deformable structure with closed-cell foam substrate together. The mechanical behaviors of such materials, including the thermoplastic polyolefin membrane, reinforcement scrim, low modulus closed-cell foam and fiber-glass stiffened facer sheets, were characterized and exanimated at controlled velocity indention and impact conditions. A finite element model is developed to simulate dynamic stress distributions in layered foam composite panels subjected to severe impact events, e.g., hail and hard object strikes. In order to build an integrated layered foam composite panel model, separate sub-models are developed that include: the polymeric matrix membrane, reinforcement scrim, low modulus closed-cell foam and fiber-glass stiffened facer sheets. A Mooney-Rivlin model of the polymeric matrix membrane is utilized to simulate the membrane’s large-deformation mechanical response during simple impact tests. The failure mode and criterion of each individual component in this layered foam composite system had been evaluated and quantified. Straightforward force-contact measurements on the reinforced polymer membrane composite material and low modulus foam backing, using spherical indenters, are shown to provide sufficient material properties for the impact model of interest. It is demonstrated that the local failure modes for the layered foam composite system can be characterized by using relatively simple failure criterion for each of the individual component layers in this type of system. Excellent correlation is obtained between model predictions and experimental dynamic impact/indentation tests.

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