All ETDs from UAB

Advisory Committee Chair

Uday K Vaidya

Advisory Committee Members

Brian S Pillay

Haibin Ning

Lee G Moradi

Mark L Weaver

Document Type

Dissertation

Date of Award

2015

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

Thermoplastic composites are used extensively in automotive, mass transit, aerospace and other commercial industries. Current industry usage is typically limited to short fiber composites formed by injection molding processes, and continuous fiber reinforced composites through processes such as autoclave molding, filament winding etc. Long fiber thermoplastics (LFT) are a class of composites known for their specific strength, corrosion resistance, impact and damping properties, as well as high production rates, recyclability, and ability for complex part fabrication. The overall objective of this research was to investigate viability of joining and assembly with long fiber thermoplastic composites. This research deals with (1) investigation of pullout resistance of nails and screws from long fiber thermoplastic composite panels that can be used for roofing construction, (2) investigation of long fiber thermoplastic composite threaded fasteners, focusing on microstructure, processing methods and mechanical performance, (3) development of mathematical and finite element model for pullout performance of long fiber thermoplastic composite threaded fasteners. Section (1) of the manuscript deals with a study comparing long fiber thermoplastic composite panels to plywood in terms of fastener pullout performance. The study found that LFT composites had pullout resistance on the order of two to three times of the best performing plywood for both nail and screw withdrawals. Section (2) of the manuscript explored the processing methods in relation to fiber alignment and its influence on the strength of the threaded fasteners. The study compared molded specimen to machined specimen and their tensile performance. The analytical model of section (3) of the manuscript investigates an approximation for LFT strength using fiber efficiency factor developed by Cox and Krenchel along with individual constituent properties. The analytical model and finite element model provided an insight into modeling of LFT threads while the experimental data validated the model for PA66 and PPS composite fasteners. Keywords:

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