Thermo-mechanical characterisation of low density carbon foams and composite materials for the ATLAS upgrade

Isaac, Bonad (2012) Thermo-mechanical characterisation of low density carbon foams and composite materials for the ATLAS upgrade. PhD thesis, University of Glasgow.

Abstract

As a result of the need to increase the luminosity of the Large Hadron Collider (LHC)
at CERN-Geneva by 2020, the ATLAS detector requires an upgraded inner tracker. Upgrading
the ATLAS experiment is essential due to higher radiation levels and high particle
occupancies. The design of this improved inner tracker detector involves development of
silicon sensors and their support structures. These support structures need to have well understood
thermal properties and be dimensionally stable in order to allow efficient cooling
of the silicon and accurate track reconstruction. The work presented in this thesis is an investigation
which aims to qualitatively characterise the thermal and mechanical properties
of the materials involved in the design of the inner tracker of the ATLAS upgrade. These
materials are silicon carbide foam (SiC foam), low density carbon foams such as PocoFoam
and Allcomp foam, Thermal Pyrolytic Graphite (TPG), carbon/carbon and Carbon Fibre Reinforced
Polymer (CFRP). The work involves the design of a steady state in-plane and a
steady state transverse thermal conductivity measurement systems and the design of a mechanical
system capable of accurately measuring material stress-strain characteristics. The
in-plane measurement system is used in a vacuum vessel, with a vacuum of approximately
10¡5 mbar, and over a temperature range from -30±C to 20±C. The transverse and mechanical
systems are used at room pressure and temperature. The mechanical system is designed so
that it measures mechanical properties at low stress below 30MPa. The basic concepts used
to design these measurement systems and all the details concerning their operations and implementations
are described. The thermal measurements were performed at the Physics and
Astronomy department of the University of Glasgow while the mechanical measurements
were performed at the Advanced Materials Technology department, at the Rutherford Appleton
Laboratory (RAL). Essential considerations about the measurement capabilities and
experimental issues are presented together with experimental results. The values obtained
for the materials with well understood properties agree well with the values available in
the literature, confirming the reliability of the measurement systems. Additionally, a Finite
Element Analysis (FEA) is performed to predict the thermal and mechanical properties of
PocoFoam. The foam is created by generating spherical bubbles randomly in the computational
tool MatLab according to the topology of PocoFoam. The model is transferred to the
CAD program Solid works to be extruded and be transformed into PocoFoam. It is later on
transferred to the FEA tool ANSYS to be analysed. Simulations of a specimen of density
equal to 0.60g/cm3 are performed and the results are compared with the values measured for
a specimen of density equal to 0.56g/cm3. The simulated results agree within 32% with the
experimental values. The experimental results achieved in the studies undertaken in thesis
have made a considerable contribution to the R&D of the stave design by helping to understand
and optimise the current stave design and explore new design possibilities. The stave
is a mechanical support with integrated cooling onto which the silicon sensors are directly
glued.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Bates, Dr. Richard
• Date of Award: 2012
• Depositing User: Dr Isaac Bonad
• Unique ID: glathesis:2012-3341
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 26 Apr 2012
• Last Modified: 10 Dec 2012 14:06
• URI: https://theses.gla.ac.uk/id/eprint/3341