Banca de DEFESA: Karoline Sales de Oliveira Gusmão

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Karoline Sales de Oliveira Gusmão
DATE: 28/07/2023
TIME: 09:00
LOCAL: Plataforma Microsoft Teams
TITLE:

MECHANICAL CHARACTERIZATION OF POLYPROPYLENE: INDENTATION, TENSILE AND FATIGUE ANALYSIS

KEY WORDS:

Indentation, Tensile ,Uniaxial Fatigue, Material properties, Polypropylene.

PAGES: 64
BIG AREA: Engenharias
AREA: Engenharia Mecânica
SUMMARY:

This study aims to enhance the understanding of the mechanical properties of polypropylene
(PP), a widely used thermoplastic polymer, by investigating its behavior under various
loading conditions. PP was chosen for its biocompatibility, biostability, and mechanical
strength, in addition to its extensive use in the packaging industry. However, the current
understanding of its mechanical behavior remains incomplete, limiting its widespread application.
Several factors, such as crystallinity, molecular weight, environmental conditions
(temperature and humidity), and loading conditions (strain rate and cyclic loading), influence
the performance of PP.
To comprehensively understand its mechanical behavior, the study conducts various mechanical
tests, including monotonic and cyclic loading tests in tension, as well as indentation
tests for compression analysis. These tests evaluate important mechanical properties such
as Young’s modulus, Tensile strength, Ultimate stress, Plastic coefficient, Fatigue strength,
Compression strength and Hardness. Additionally, the study explores the influence of temperature
and displacement rate on the mechanical properties of PP.
Thus, the study concludes by presenting an analysis of the mechanical behavior of pure
PP, identifying the material’s hardness under a range of loads from 100 N to 400 N using a
5 mm diameter spherical indenter, and from 500 N to 2 kN using a 15 mm diameter spherical
indenter to assess the material’s elastic properties under compression. The present study
investigates the mechanical properties of polypropylene under various loading conditions,
revealing a yield stress of approximately 30 MPa in compression tests and rate-dependent
behavior in tensile tests. These findings underscore the importance of considering loading
rates when assessing the material’s performance and behavior.Moreover, the observed yield
stress,σy , and maximum tensile stress, σu, are 5.9 ± 0.5 MPa and 19.0 ± 0.5 MPa, respectively,
through monotonic tests at different strain rates (2 mm/min and 6 mm/min). The
tensile tests revealed a dependence of the modulus of elasticity, E, on the displacement rate,
with values of 1357.95 ± 8.2 MPa for 2 mm/min and 1173.9 ± 12.3 MPa for 6 mm/min.
By conducting fatigue tests at different temperatures (24 °C ± 2 °C and 30 °C ± 2 °C
at 1 Hz), a significant increase in the number of cycles was observed as the temperature
decreased. Notably, a substantial similarity in the number of cycles to failure was observed
between extreme loading values at different temperatures, showing close values for 80% σu
at 30°C ± 2°C and 95% σu at 24 °C ± 2 °C.

COMMITTEE MEMBERS:
Externo à Instituição - SÉRGIO HENRIQUE PEZZIN - UDESC
Interno - 1646090 - FABIO COMES DE CASTRO
Interno - 1249764 - JORGE LUIZ DE ALMEIDA FERREIRA
Presidente - 2143651 - THIAGO DE CARVALHO RODRIGUES DOCA