– Graduation Assignment –

Simulating Bundle Spreading for TapeManufacturing

University of TwenteFaculty of Engineering Technology

Mechanics of Solids, Surfaces and Systems

Introduction

The use of thermoplastic composites for aircraftstructures has been steadily growing since the in-troduction in the 1980s. Where initial applicationswere mainly limited to secondary parts, such asclips and brackets, the industry is currently consid-ering thermoplastic composites for larger structuressuch as the fuselage and wings. The interest forthese larger structures is partly driven by the intro-duction of high-end unidirectional tape materials.The manufacturing of these pre-impregnated tapematerials is not straightforward, however, and reliesto a large extent on trial-and-error procedures. Thecosts and time associated with tape development ishigh, while a lack of process control may lead tobatch-to-batch variability.

Broadly, thermoplastic composite tape manufac-turing can be subdivided into three steps, namely i.bundle spreading, ii. impregnation and iii. consol-idation. The first step involves the manipulation ofthe dry fiber bundles in order to ease impregnationand to obtain the desired thickness. It is a crucialstep as it affects not only the following impregna-tion process, but also the resulting tape morphologyand, hence, its mechanical properties and process-ability.

Objective

Generally speaking, bundle spreading is achievedusing a series of spreader bars, as for example shownin Figure 1. Predictive models for the spreadingprocess could help reduce the time and costs re-quired for tape manufacturing, while also providingthe means to optimize tape morphology and hencethe properties. The objective of this assignmenttherefore is to develop a simulation model for thetape spreading process. The model should be ableto predict the shape of the spreaded bundle as wellas the occurrence of fiber breakage, and include theeffects of friction and spreader bar geometry.

Figure 1: Spreading of a carbon bundle (from: Schnabelet al.).

Approach

A basic model, implemented in Python, has beendeveloped in earlier work. It describes the cross-section of a fiber bundle and is based on the Dis-crete Element Method, as is illustrated in Figure 2.As a first step, a collection of spreader bar geome-tries needs to be implemented. Secondly, the modelshould be extended to include the effects of fric-tion between the fibers and between the fibers andspreader bar. As a last step, if time allows, quasi-3D effects can be included by considering multiplecross-sections along the fiber bundle. An experi-mental setup is available to provide data for modelvalidation.

Figure 2: Simulated bundle spreading.

Interested?

Feel free to contact Wouter Grouve (N-206 orw.j.b.grouve@utwente.nl) for more information.