عنوان

Additive Manufacturing of Two Phase Thermoplastic Composites:

شماره

TLpq2309792160

زبان متن نوشتاري يا گفتاري و مانند آن

انگلیسی

عنوان اصلي

Additive Manufacturing of Two Phase Thermoplastic Composites:

نام عام مواد

[Thesis]

نام نخستين پديدآور

Papon, Md. Easir Arafat

عنوان اصلي به قلم نويسنده ديگر

A Process Model, Microstructure and Performance Study

نام ساير پديدآوران

Haque, Anwarul

نام ناشر، پخش کننده و غيره

The University of Alabama

تاریخ نشرو بخش و غیره

2019

نام خاص و کميت اثر

291

جزئيات پايان نامه و نوع درجه آن

Ph.D.

کسي که مدرک را اعطا کرده

The University of Alabama

امتياز متن

2019

متن يادداشت

Fused filament fabrication (FFF) based additive manufacturing (AM) of polymers and composites is a growing interest in processing tailorable parts with functional requirements like structural integrity, lightweight, high-temperature capability, etc. In general, the parts manufactured by FFF show large void contents, weak bonding, and inferior structural performance in comparison to those produced by conventional methods. The present research focused on overcoming the shortcomings of FFF through process modeling, microstructure study, and performance analysis. An experimental and numerical study has been conducted on the FFF of carbon fiber reinforced polylactic acid (CF/PLA) composites. A computational fluid dynamics (CFD) based numerical model was developed to simulate the temperature distribution and melt flow characteristics of highly viscous polymer (single and two-phase composites) using non-Newtonian computational model. Free space bead flow geometry and bead spreading architecture on the platform were also simulated with various nozzle geometries. The effects of the circular, square, and star-shaped geometries on bead cross-sectional shapes were studied both numerically and experimentally to achieve less void contents and improve the bead/layer bonding. Different dominant FFF process variables, both in filament extrusion and part production steps were studied, and a multi-level experimentation scheme was developed to study the bead-level to part-level properties. Physics-based surrogate models were developed, and stochastic uncertainty analysis was carried out on the manufacturing process to build up an optimum process-structure relationship. Another criticality of fiber-matrix interfacial bonding in the FFF-composites was addressed by introducing proper surface treatment to the fibers and post-manufacturing thermal treatment. The numerical model showed good promise in tailoring the bead geometry with the square and star-exit nozzle that potentially enhanced the bead to bead bonding. Extensive experimental studies were conducted to characterize strength, stiffness, fracture toughness, and void contents with various printed layer orientations and fiber concentrations of the FFF coupons. An acid-based functionalization of fibers, printing using square-nozzle, and enhanced crystallinity through controlled annealing were found to improve the fiber-matrix and inter-bead bonding, reduce the inter and intra-void and improve mechanical performances. The optimization and experimental data-driven stochastic modeling of the process parameters paved the way for producing parts with greater confidence at reduced experimental affords. The investigations and strategies developed in this dissertation will help to establish a high-quality and efficient process framework to improve the performance of additively manufactured two-phase composites. The fundamental understating and knowledge exercised in this dissertation can potentially be used for any polymer-based AM processes beyond the FFF since the fundamental challenges of controlling the voids and bonding are unavoidable.

موضوع مستند نشده

Aerospace engineering

موضوع مستند نشده

Materials science

موضوع مستند نشده

Mechanics

موضوع مستند نشده

Plastics

موضوع مستند نشده

Thermodynamics

مستند نام اشخاص تاييد نشده

Haque, Anwarul

مستند نام اشخاص تاييد نشده

Papon, Md. Easir Arafat

نام الکترونيکي

فرمت انتشار

p

نوع ماده

[Thesis]

کد کاربرگه

276903

سطح دسترسي

a

تكميل شده

Y