Civil Engineering ETDs

Publication Date

Summer 7-13-2017



Carbon fiber reinforced polymer (CFRP) composites have been attractive materials for many civil and mechanical applications. However, the high cost of carbon fibers has hindered its wide spread in many civil and structural applications. Furthermore, CFRP composites have been mostly disposed of in landfills after their end of service life, creating environmental concerns and potential release of toxic byproducts. A significant interest in recycling composites has appeared in the last decade for obtaining recycled carbon fiber. A process based on wet chemical degradation and thermal treatments of FRP composites showed the ability to produce recycled carbon fibers with 99% purity and properties near those of virgin fibers. The recycled carbon fibers are about 20% of the cost of new carbon fibers.

This Thesis, discusses the use of recycled carbon fibers produced using the above recycling process to produce new CFRP composites. Also, the effect of fiber length and composite volume fraction on the tensile strength of the short fiber reinforced polymer is investigated. Moreover, methods of fabricating a new recycled CFRP composite using recycled carbon fibers is discussed. Two types of recycled composites are tested and compared with neat carbon fiber plain weave composite with similar composite density. Those two types include recycled CFRP produced using neat epoxy and recycled CFRP produced using COOH functionalized multi-wall carbon nanotubes (MWCNTs). The objective of including MWCNTs is to improve the interfacial shear transfer in the recycled CFRP composite. We show that the new recycled CFRP composites have comparable tensile strength to the on-axis strength of plain weave CFRP composite. The significance of fiber volume fraction and MWCNTs content on the behavior of the recycled CFRP composite are also discussed. An analytical model to predict rCFRP strength and stiffness (elastic modulus) is presented and used to explain the experimental observations.


Recycled Carbon fiber, Composite, Multi walled carbon nano tubes

Document Type




Degree Name

Civil Engineering

Level of Degree


Department Name

Civil Engineering

First Committee Member (Chair)

Mahmoud Reda Taha

Second Committee Member

Mehran Tehrani

Third Committee Member

Fernando Moreu Alonso