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Advisory Committee Chair

Haibin Ning

Advisory Committee Members

Shane Aaron Catledge

Selvum Brian Pillay

Document Type

Thesis

Date of Award

2023

Degree Name by School

Master of Science in Materials Engineering (MSMtE) School of Engineering

Abstract

The overmolding process is one of the newly developed composite processing methods which allow to integrate continuous and discontinuous fiber reinforced composites for weight and cost reduction for a variety of applications. Continuous fiber reinforced thermoplastics (CFRTs) exhibit excellent mechanical properties such as high impact strength and stiffness, however forming them into complex shapes is challenging and the processing cost is high. On the other hand, the processing of discontinuous fiber reinforced composites, including long fiber reinforced thermoplastics (LFTs), into complex shapes is relatively easy compared to continuous fiber composites because of their high processibility. The integration of both continuous and discontinuous fiber reinforced composites can take advantage of the good processibility of the discontinuous fiber reinforced composite and the excellent mechanical properties of the continuous fiber reinforced composite. While CFRTs increase the mechanical properties of a part, LFTs provide design freedom and enable the production of complex shapes. This process results in additional weight reduction without compromising mechanical properties of parts. Hence, this technique can allow thermoplastic matrix composite material to replace some conventional materials, which are heavier and exhibit insufficient mechanical properties. There are several processing parameters in the over-molding process: charge temperature, mold temperature, overmolding pressure, and molding cycle time. These parameters result in the complexity of the process and significantly affect the quality of the product. Therefore, it is very important to use the appropriate processing parameters to ensure the quality of products in overmolding process. If the bonding does not provide the required mechanical properties for working conditions, delamination occurs and can lead to failure. This study investigates the effects of processing conditions on the quality of the bond surface of overmolded composite using a non-destructive technique, namely GrindoSonic test. Micro CT was also used to evaluate the fiber orientation in the overmolded composite. For this purpose, several hybrid composite plates were produced using overmolding and the dynamic flexural modulus of these plates was determined using the GrindoSonic method. It was concluded that mold temperature and extruder temperature positively affected bond quality. Additionally, comparing the dynamic flexural modulus of LFT and overmolded samples has revealed that the mechanical properties of composites can be slightly increased using the overmolding method.

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