1 research outputs found
Life Cycle Impact of Different Joining Decisions on Vehicle Recycling
Stricter vehicle emission legislation has driven significant
reduction in environmental impact of the vehicle use phase
through increasing use of lightweight materials and
multi-material concepts to reduce the vehicle mass. The joining
techniques used for joining multi-material designs has led to
reduction in efficiency of the current shredder-based recycling
practices. This thesis quantifies this reduction in efficiency
using data captured from industrial recycling trials.
Life Cycle Assessment has been widely used to assess the
environmental impact throughout the vehicle life cycle stages.
Although there is significant research on material selection or
substitution to improve the vehicle’s carbon footprint, the
correlation between multi-material vehicle designs and the
material separation through commonly used shredding process is
not well captured in the current analysis. This thesis addresses
this gap using data captured from industrial trials to measure
the influence of different joining techniques on material
recycling efficiencies. The effects of material degradation due
to joining choices are examined using the life cycle analysis
including exergy losses to account for a closed-loop system. The
System Dynamics approach is then performed to demonstrate the
dynamic life cycle impact of joining choices used for new
multi-material vehicle designs.
Observations from the case studies conducted in Australia and
Europe showed that mechanical fasteners, particularly machine
screws, are increasingly used to join different material types
and are less likely to be perfectly liberated during the
shredding process. The characteristics of joints, such as joint
strength, material type, size, diameter, location, temperature
resistance, protrusion level, and surface smoothness, have an
influence on the material liberation in the current sorting
practices. Additionally, the liberation of joints is also
affected by the density and thickness of materials being joined.
The life cycle analysis including exergy losses shows a
significant environmental burden caused by the amount of
impurities and valuable material losses due to unliberated
joints. By measuring the influence of joints quantitatively, this
work has looked at the potential of improving the quality of
materials recycled from ELV to be reused in a closed-loop system.
The dynamic behaviours between the joining choices and their
delayed influence on material recycling efficiencies from the
life cycle perspective are performed using the data from case
studies. It shows that the short-term reduction in environmental
impact through multi-material structures is offset over the
long-term by the increasing impurities and valuable material
losses due to unliberated joints. The different vehicle recycling
systems can then be resembled using two widely known system
archetypes: “Fixes that Fail” and “Shifting the Burden”.
Despite the adoption of more rigorous recycling approaches, the
life cycle impact of different joining techniques on vehicle
recycling continue to exist. The enactment of strict regulations
in current ELV recycling systems is unable to solve the
underlying ELV waste problem, and only prolongs the delay in
material degradation due to joining choices. This work shows that
the choice of joining techniques used for multi-material vehicle
designs has a significant impact on the environmental performance
during the ELV recycling phase