Ulrich Sachs

PhD Project

Complex Stamp Forming: Explore the frictional behavior of fiber-reinforced thermoplastics in process conditions above melt point.

Start / End:

January 2010 to January 2014


2014 - Senior Research Associate at TPRC (The Netherlands)



PhD Thesis

Ulrich Sachs (2014). Friction and bending in thermoplastic composites forming processes. PhD Thesis, University of Twente, The Netherlands, ISBN 978-94-6259-483-8.

Summary of PhD Thesis

With the demand for better fuel economy in the aerospace and automotive industries, lightweight polymer matrix composites became an attractive alternative for metal structures. Despite the inherently higher toughness and impact damage resistance of thermoplastics, thermoset matrix composites are used in the majority of applications. This is largely attributable to the higher material costs of thermoplastic composites and the limited experience with these materials. The ability to re-melt thermoplastics, however, allows automated processing methods with short cycle times, which lowers production costs to a competitive level, especially for larger series production.

Thermoforming of flat laminates of continuous fiber reinforced thermoplastic laminates into 3-D parts is a complex process. Fundamental understanding of the deformation processes is needed to prevent process induced defects, such as wrinkling at critical locations, for the product or the process. The elementary deformation mechanisms need to be addressed one-by-one to develop this understanding and to translate this understanding to reliable Computer Aided Engineering tools for predictable product development processes. The major deformation mechanisms of continuous fiber reinforced composites are considered to be intra-ply shear, inter-ply slippage and ply bending. The latter two are investigated in this thesis. The objective of this thesis is to develop an understanding of the physics of the deformation mechanisms and to make it available in the form of describing constitutive equations.