Year

2021

Season

Spring

Paper Type

Master's Thesis

College

College of Computing, Engineering & Construction

Degree Name

Master of Science in Mechanical Engineering (MSME)

Department

Engineering

NACO controlled Corporate Body

University of North Florida. School of Engineering

First Advisor

Dr. Stephen Stagon

Second Advisor

Dr. Jutima Simsiriwong

Rights Statement

http://rightsstatements.org/vocab/InC/1.0/

Third Advisor

Dr. Grant Bevill

Abstract

The metallization or metallic reinforcement of polymer parts has been widely used in industry for several decades. Polymer parts are classically metalized for aesthetics, chemical and thermal resistance, electrical conductivity, and mechanical strength. Metallization has been shown to increase strength of polymer parts when compared to the strength of the bulk material without metallization. Additive manufacturing (AM) techniques that have emerged in the last few decades produce parts with different surface features and chemistry than the typical polymer part produced through injection molding. AM parts are typically weaker than traditionally manufactured parts from the same material due to intrinsic details and layer interaction. Like their traditionally manufactured counterparts, AM parts will greatly benefit from metallization, but the traditional processes of metallization do not transfer to AM parts due to surface chemistry differences. This work aims to develop processing modalities for the metallization of 3D printed polymer parts from vat polymerization methods. The metallic reinforcement process is done through sequential deposition of a thick structural nickel plating applied to a conductive physical vapor deposition (PVD) strike layer of nickel that is deposited directly onto the surface of 3d printed cyanate ester polymer base. The resulting structure is a metal-polymer sandwich composition. The overall stress transfer that the composite can experience is dependent on the adhesion strength of the two interface layers (PVD strike to Cyanate Ester, and Nickel Plating to PVD Strike). The performance of the sandwich composite structures are strongly dependent on the adhesion between both of these interfaces, and prior work by Bray et al. in 2019 demonstrated a method of optimizing the adhesion of the PVD strike to the polymer part. However, the presented processing maximized adhesion strength of the Cyanate ester to the PVD strike but came at the reduction of the nickel to PVD strike 13 interface strength, as the mechanics that increased the sputtered film’s adhesion also blocked the mechanics that allowed the Nickel plating to adhere. This work first explores the mechanisms of adhesion of the PVD strike to the polymer part and uncovers two new phenomena associated with the cyanate ester material that had been previously unknown. The two mechanisms are determined to be advantageous to the strength of the core cyanate ester part but extremely detrimental to the adhesion of the Ni electroplated layer to the PVD strike. The core action of the mechanism is through the percolation and egress of uncured monomer through the PVD strike, resulting in near encapsulation and strong adhesion of the PVD strike to the part but metallic bonding between the PVD strike and the electroplated Ni. After presenting this new understanding, the author concludes with the proposal of an evidence-based processing method for the successful metallization of the cyanate ester parts.

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