IMC SEMINAR:Process Analysis Of Manufacturing Composites Structures

SEMINAR ANNOUNCEMENT :

Title                : Process Analysis Of Manufacturing Composites Structures

Speaker         : Thomas CENDER

Time               : November 28, 2018, 13:40-14:30

Place              : Teknopark- KTMM

Abstract: 

Manufacturing high performance structures of composite materials is a  multidisciplinary engineering field which calls upon topics in heat and  mass transport as well as material science. The objective of processing  polymer composites is to produce consolidated laminate structures where  fiber reinforcement is embedded within a continuous polymer matrix. Because of rich physics involved, and the variety of available  processes, composites manufacturing remains an active area of research  interest.

The first part of this seminar is dedicated to the discussion voids  which form from gases entrained in the polymer matrix during processing  of prepregs (preimpregnated fiber plies). Prepregs, whether they be  thermoset or thermoplastic, do not require (or rather do not allow) a  net flow process of the polymer matrix. Therefore, entrapped gases can  only be extracted through open porosity in the fiber/resin network. A  process model is developed, based on the physics of gas flow in porous  media, in order to optimized the conditions for gas extraction. In a further extension, a multiphase flow model is developed to couple the interaction of the liquid resin phase with the gas phase.

The second part of the seminar focuses on processes involving  thermoplastics. Similar to the first section, thermoplastic composites  are formed from prepreg plies. The high viscosity of thermoplastics  preclude them from infusion processes often used with thermosetting  resins. Instead, thermoplastics rely on lamination processes in order to  build structures. This lamination process (also known as thermoplastic welding) involves pressing layers together while heat is focused at the  material interface. Adhesion of layers requires good intimate contact of the interface, followed by auto-adhesion of the polymer. Auto-adhesion (interface healing) occurs when long thermoplastic molecular chains,  through continuous random fluctuations known an reptation, will entangle  with molecules across the interface. In this work, the welding of  thermoplastic composite samples is evaluated experimentally. Samples of PEKK composite were welded on a custom benchtop apparatus. The effect of  welding time was evaluated by the fracture energy of interface--partial  healing is defined by a fracture energy lower than that of the bulk  polymer. Insight into molecular interactions was gained via rheological  analysis of the viscoelastic behavior of the polymer melt. Due to the  high temperatures required to melt PEKK (and other PAEK polymers),  crosslinking of the polymer backbone occurs at the required processing  temperatures. It was discovered that the relaxation time will evolve by  an order of magnitude every hour; the implication is that preprocessing  of elementary parts (e.g. autoclave processing) will degrade their  ability weld in the subsequent joining process. The results were  integrated into a coupled heat transfer model developed in FreeFEM++  (along with polymer crystallization) in order to define a processing window. The approach taken in this work can also be applied to the FDM  3D printing process in order to validate the printability of a given polymer.

Biograph:

Tom completed his PhD in Mechanical Engineering at the University of Delaware while conducting his thesis work at the Center for Composite Materials. His research focused on flow processes in forming fiber reinforced polymeric composite structures, where understanding the transport of gases, liquid resin, and bubbles are important for producing fully consolidated (low void content) composite materials. Interim to his PhD, he spent some months as a visiting researcher at the University of Bristol's Advanced Composites Collaboration for Innovation and Science, as well as with Pratt and Whitney's MPE Composites Group. Currently he is a postdoctoral fellow with the Laboratory for Energy and Thermal Sciences (LTeN) at the University of Nantes and the IRT Jules Verne in Nantes, France, where he is studying continuous thermoplastic welding of composite structures.

Kampüs-Teknopark Arası Araç Bilgisi:

Sabancı Üniversitesi -Teknopark Gidiş 

Teknopark- Sabancı Üniversitesi Dönüş

Araç Hareket Alanı : KTMM Binası Önü