Date of Award

Summer 2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Oleksandr Kravchenko

Committee Member

Krishnanand N. Kaipa

Committee Member

Sergii Kravchenko

Committee Member

Gene Hou

Abstract

Fiber-reinforced composites are available in various material systems, each requiring specific manufacturing techniques to exploit their unique properties fully. Systems such as woven fabrics and preimpregnated fibers employ distinctive methods to harness these properties effectively. For instance, non-crimp fabrics (NCF) use high-pressure resin transfer molding and prepregs, like IM7-8552, use manufacturing method called automated fiber placement (AFP). However, these manufacturing processes often introduce deposition features that can evolve into defects. Their occurrence and impact on morphology must be predicted using experimentally informed finite element models. The research began with compaction experiments on NCF fabric, leading to the development of a constitutive equation for an FEA model that simulated the evolution of fiber volume fraction and wrinkling between the woven fabric layers. The model highlighted the strain-rate dependence on fiber volume fraction distribution across NCF layers. The study then focused on the deposition of a prepreg tow on a composite substrate, modeled using a visco-hyperelastic constitutive equation with an anisotropic tensorial viscosity. This was coupled with a thermo-rheological model to predict heat transfer and resin development within the composite layers. Experiments with increasing substrate layers were conducted, with the spreading of the tow recorded in both experimental trials and numerical models. The substrate layers influenced the compaction and temperature gradient, affecting the substrate's viscous properties. After deposition, the visco-hyperelastic model was validated during early curing phases by creating and measuring unidirectional composite coupons, comparing this data to similar models. A laminate with a single fiber tow gap was also studied, revealing discrepancies in predicting resin rich region volumes. Incorporating resin bleed-out into the model improved accuracy by accounting for fiber volume fraction evolution and internal pressure in the fiber tow gap, providing structural support to the sinking plies. The addition of the resin bleed out results in a more accurate model prediction. The research culminates in attempting to predict the morphology of a laminate with multiple fiber tow gaps. Although the previous concepts were applied, they did not accurately predict the laminate's morphology, indicating potential for further research and the development of new concepts to simulate the composite manufacturing process accurately.

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DOI

10.25777/9af5-fd45

ISBN

9798384456469

ORCID

0000-0001-9477-0986

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