Dynamic response and failure in layered structures and composites

Chenghua Han, Purdue University

Abstract

Layered structures or media and their constituent materials—composite laminates have been studied. Topics discussed include attenuation of stress wave propagation in periodically layered elastic media, pre-stress effect on layered plates consisting of a hard and brittle phase (glass) and a soft phase (aluminum) subjected to dynamic contact loading, simulation of the conic fracture in the brittle phase and investigation of the material fracture toughness in the presence of thermal residual stresses, and Mode I dynamically propagating delamination crack in composite laminates. An exact viscoelastic analogy for a periodically layered elastic media was introduced, and a short-time relaxation function was developed. Both the wave front decay and the spatial attenuation of stress waves in a periodically layered medium were studied. The effects of thickness ratio of the two constituent layers and other parameters on the attenuation of stress wave propagation were examined. Pre-stressed layered-plates, consisting of brittle glass and ductile aluminum layers, were fabricated and tested under both static and dynamic contact loading. The effect of pre-stress on the layered plates has been identified. The conic cracking in the glass layer was modeled in linear elastic fracture mechanics. Mode mixity and fracture toughness of the conic crack in the presence of thermal pre-stress were computed. Mode I dynamic delamination of composite laminates was studied via the WIF method on SHPB apparatus. The high speed of Mode I delamination crack propagation was achieved, and the dynamic delamination crack propagation was modeled by a finite element method. The dynamic initiation fracture toughness, and the relation between the dynamic strain energy release rate and the delamination crack propagation speed were examined.

Degree

Ph.D.

Advisors

Sun, Purdue University.

Subject Area

Mechanics|Mechanical engineering

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