Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Master of Engineering Science


Mechanical and Materials Engineering


Kuboki, Takashi

2nd Supervisor

Wood, Jeffrey T



The D-LFT process is an efficient and cost-effective process and includes two twin-screwextruders, a conveyer, and a compression molding machine. It is imperative to understand how the process sequence affects molecular weight and thermal properties of composite materials during the D-LFT process. The main objective of this study was to characterize variation in molecular weight and thermal properties of two types of polyamide (PA)-based composite materials (glass fiber reinforced PA6 composites and carbon fiber reinforced PA66 composites) through the D-LFT process. Samples were taken from different locations along the D-LFT process and characterized using triple detection gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), andfourier-transform infrared spectroscopy (FTIR). It was found thatmolecular weightof both PA-based composites increased after the second extruderby branching of PA molecules. Therefore, process conditions after the secondextruderneed to be carefully adjusted to design PA-based D-LFT products.

Summary for Lay Audience

Driven by economic, legislative and market considerations, light weight design has become one of the core design principles in transportation industry all around the globe in the last few decades. Composite materials have emerged as a front running solution to the light-weighting challenge, as they are lighter than othercompetitormaterials such as steel and aluminum and can be tailor-made to a specific application. The direct long-fiber reinforced thermoplastic (D-LFT) process is an efficient and cost-effective process to manufacture long-fiber reinforced thermoplastics. Polyamide (PA)-based composite materials manufactured through the D-LFT process are good candidates to be used for products where mechanical and thermal loadings are exerted. In this study, thermal properties of two types of PA-based composite materials were investigated at different locations along the D-LFT process, and the process location that is important to design PA-based D-LFT products was identified.