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|Title: ||Study on the structure-property relationship of rubber toughened and short glass fibre reinforced ternary composites|
|Other Titles: ||Xiang jiao zeng ren ji duan bo li xian wei zeng qiang zhi san yuan fu he cai liao de jie gou ji xing neng guan xi fen xi|
|Authors: ||Wong, Shuk Ping (黃淑萍)|
|Department: ||Department of Physics and Materials Science|
|Degree: ||Master of Philosophy|
|Issue Date: ||2008|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Polymeric composites -- Mechanical properties.|
Fibrous composites -- Mechanical properties.
|Notes: ||CityU Call Number: TA455.P58 W65 2008|
xv, 94 leaves : ill. (some col.) 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2008.
Includes bibliographical references (leaves 83-94)
|Abstract: ||In ternary composite systems, it is widely accepted that the impact and the tensile
behaviors can be optimized by incorporating both elastomer and short glass fiber (SGF).
However, in order to achieve property synergism of these multicomponent systems, the
structure-property relationships knowledge is usually required. The mechanical
properties are, in fact, not only controlled by the amount of additional phases added,
but also the structure of the fiber-matrix interface morphology. The aims of this
research work are to gain a deep understanding on the effect of morphologies of ternary
composites on mechanical properties and their fracture mechanisms. Two main types of
ternary composites have been prepared for investigation:
1) Polypropylene/SEBS-rubber/Short-Glass-Fibre (PP/SEBS/SGF) Ternary
(HDPE/PB-g-MA/SGF) Ternary Composites
Structural and morphological tests have been carried out on the PP/SEBS/SGF ternary
blends. The mechanical properties of the blends were studied by tensile test, Charpy
impact test and fracture toughness measurement. The micro-structural features, fracture
mechanisms, glass fibre length and orientation, etc., were examined with the help of
optical microscopy (OM) and scanning electron microscopy (SEM).
By controlling the fiber surface to be in direct contact with the rubber or the
thermoplastic matrix (i.e. PP or HDPE), two different types of morphologies have been
obtained by employing the functional group maleic anhydride (MA) as the interface controlling agent. The main morphologies developed in the resulting ternary
(i) A portion of elastomer encapsulates the glass fibers surface while the remaining
portion is dispersed finely in the thermoplastic matrix. These systems are
referred to as the encapsulated structure in this work
(ii) All glass fibers and the elastomers are evenly dispersed in the matrix. These
systems are referred to as the separate dispersion structure in this work
It is observed that the mechanical behaviors of ternary composites having the two types
of microstructures are distinct, irrespective of the polymer matrix (i.e. PP or HDPE)
used. Composites with separate dispersion structure exhibit higher impact toughness,
higher yield strength but much smaller elongation at break than that of the encapsulated
The essential work of fracture (EWF) technique was used to determine the fracture
toughness characteristics of the PP/SEBS/SGF hybrid composites. Similar to the
conventional mechanical tests, composites with encapsulation structure have noticeably
higher extensibility, determined by higher value of non-essential plastic work (;wp)
while the separate dispersion structure composites are characterized by higher fracture
toughness, denoted by the higher value of specific essential fracture work (we).
However, as the fibre content increases from 10 wt% to 20 wt%, the properties between
the two morphologies are similar since the degree of matrix plastic deformation was
constrained by increasing the glass fibre content.
Microscopic evaluations as well as four point bending test were performed to study the
deformation mechanisms of the PP/SEBS/SGF composites. The results of fractographic analysis indicate that the dominant fracture mechanism of both structures is massive
shear bands. Besides, remarkable interfacial debonding and mild rubber cavitations
were observed for the composites with encapsulated structure, which would be the
cause of their excellent ductility and fair toughness.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b2339793|
|Appears in Collections:||AP - Master of Philosophy |
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