Element-free galerkin modelling for cutting of fibre reinforced plastics

Kahwash, Fadi (2017) Element-free galerkin modelling for cutting of fibre reinforced plastics. Doctoral thesis, Northumbria University.

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Abstract

The utilisation of composite materials is increasing across many industries, spurred by the need for weight reduction and improved mechanical properties. This has led to an increase in their machining requirements. Although composites are laid in near-net shape, machining processes such as drilling and edge trimming are required to give the composites parts their final geometry and functionality. Machining of composites is challenging due to their low machinability and high cost. Numerical modelling presents a valuable tool for cost reduction and better understanding of the machining processes. Most modelling of machining is carried out using the Finite Element Method, which requires significant time in generating the mesh. Meshfree methods present an attractive choice for machining simulations due to their capabilities in modelling large deformations without the need to construct a mesh.

This work aims at developing an efficient meshfree model to simulate orthogonal cutting of unidirectional composites. The Element-Free Galerkin (EFG), which is a prominent meshfree method, is used to construct the model using MATLAB. Steady-state and dynamic models are developed and validated against experimental evidence. The models include several novel features in constitutive relations, composites failure and contact modelling. The main outputs of the simulations are cutting forces and chip formation. Good agreement with experiments is achieved in predicting cutting force. However, thrust force is significantly under-estimated, which is noticed in most of the relevant literature. Three phases of orthogonal cutting experiments are carried out to gain better understanding of the cutting process and generate model validation data. Statistical significance of fibre orientation angle, depth of cut, rake angle and cutting speed on cutting forces and surface integrity is established. Furthermore, the effect of fibre volume fraction on cutting forces is investigated. This work showed that the EFG is a viable numerical method to simulate orthogonal cutting. The simple and automated preprocessing and high quality of approximation are the most advantageous features of the developed model.

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