Development of hybrid rotomoulded composite structures

This phenomenon is driven by surface tension and is known as sintering, which constitutes the fundamental mechanism by which parts are formed in rotomoulding. The complexity of sintering makes adding and combining different materials to gain part strength incredibly challenging.Combining two or more materials can create compounds of different properties, known as composites, that produce a result structure that offers more desirable properties than the separate sources.

However, no method has made standard the incorporation of reinforcements to produce composite structures using rotational moulding. The present work aims to develop effective means to reinforce rotationally moulded parts to enhance strength and mechanical performance. The work is divided into three main blocks.In block one, the work starts with determining the optimum material composition and structure.

An experimental study identifies the critical parameters of the composite part's optimum material composition and structure. The study also aids in developing a hybrid manufacturing process by defining the addition method, processing parameters and moulding technique. An experimental study focuses on how polymer particles soften, bond, and densify with reinforcing fibres.

Adhesion measurements were based on the angle formed between the liquefied resins and the reinforcing fibre bundle surface. It was discovered that by modifying heating conditions, resin viscosity, and fibre chemical surface, the adhesion of the polymer to the fibre could be wettable enhanced.In block two, the work continues developing a new in-mould visual imaging system, named RotoCam™, capable of obtaining images of the polymer during the process.

The high temperatures, bi-axial rotation, and enclosed mould complicate studying the polymer melt from the inside of the mould. An investigation into the system's main characteristics is undertaken, identifying the key features it requires and assessing the image quality and level of magnification. The layouts included developing three versions, achieving the optimum image quality and resolution to acquire measurable images from the process in the last design.

The work finishes by applying the optimum material composition, structure, and hybrid manufacturing process in a full-scale set of trials in block three. During the trials, RotoCam™ acquired images to assess fibre-polymer adhesion, validating the material and the process. The trial set comprised mouldings using the resins, fibres and processing parameters established in block one to determine the relation between fibre adhesion with composite fibre content.

Finally, conclusions and recommendations for future work are presented in the last chapter to produce the most optimum composite structure in rotational moulding.<br>