A DCAMM seminar will be presented by
Ismet Baran, Assistant Professor, Ph.D.
University of Twente
Enschede, The Netherlands
Abstract:
It is generally accepted that residual stresses in fiber reinforced polymer composites arise primarily due to the anisotropic chemical shrinkage and thermal expansion of individual plies in macro level. The different thermal expansion of individual fiber and matrix material is also one of the mechanisms generating residual stresses in micro level. The formation of residual stresses can have significant effects on the mechanical performance of composite structures by causing warpage, initiating damage such as interface debonding and matrix premature cracking. They also affect the internal stress level which plays an important role on the failure mechanism of composite structures during their service life such as crack initiation and growth.
The present seminar first focuses on the modelling of residual stress in a composite manufacturing process namely the pultrusion process. The state-of-the-art thermo-chemical and thermo-mechanical modelling strategies specifically developed for a thermosetting pultrusion are explained. The proposed models are utilized to predict the process induced stresses for various glass reinforced pultruded products such as square beam, circular rod and I-beam. Different residual stress levels and characteristics are obtained from the process simulations which are qualitatively compared with the real pultruded products.
The seminar then concentrates on the effects of thermal residual stresses on the mechanical behavior of a recently developed butt jointed AS4/PEKK thermoplastic T-stiffener under bending conditions. The thermal residual stresses are first estimated by applying a temperature gradient from the crystallization temperature to room temperature. Subsequently, the crack initiation and propagation in the butt joint as well as delamination at the skin-joint interface are simulated using a quasi-static numerical model in which the calculated thermal residual stresses are also taken in to account in model.
Danish pastry, coffee and tea will be served 15 minutes before the seminar starts.
All interested persons are invited