Date of Award

Spring 2020

Document Type

Open Access Thesis

Department

Mechanical Engineering

First Advisor

Subramani Sockalingam

Abstract

Traditional unidirectional carbon fiber reinforced polymer matrix composites exhibit brittle failure, limited toughness, and poor damage tolerance often resulting in the overdesign of composite systems. This work focuses on the automated fiber placement (AFP) manufacturing and characterization of a new family of pseudo-woven (PW) laminate architectures aimed to enhance impact resistance and damage tolerance. The PW laminate architecture uses a specialized in situ AFP process implementing tow skips to produce its laminate architecture. This results in a heterogeneous architecture possessing spatially variable in-plane material properties unlike traditional laminated composites. This heterogeneity is associated with topological variations in the fiber orientations resulting in numerous interfaces and an expanded design space. The composite laminates are produced using carbon fiber-reinforced epoxy slit tapes in a gantry-based AFP machine. The PW laminate architectures manufactured in this work are experimentally characterized for warpage, uniaxial tension, low velocity impact, and high velocity impact response.

Experimental results indicate that a 4 ply PW laminate architecture can realize warpage reductions of up to 58% compared with traditional asymmetrical laminates. This is attributed to the spatial variations in the stacking sequence resulting in variations in the B matrix components of the ABD matrix. Uniaxial tension experiments indicate that 4-ply PW laminate architectures exhibit similar strength compared to traditional composites consisting of the same fiber angles. However, they exhibit an increased strain to failure and a more complex progressive failure including multiple mesoscale cracking and crack

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