Influence of Nanoclay on Interlaminar Fracture Characterization of GFRP, and Intralaminar Fracture Characterization of SIMS & Glass Mat Reinforced Thermoplastics Materials
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Date
2020-06
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Addis Ababa University
Abstract
The needs of lightweight and customizable structural materials instigate researchers to conduct
rigorous materials characterization, with particular attention toward failure mechanisms and
safety standards, and to study the materials’ development. Furthermore, the currently available
structural and semi-structural composite materials made up of fiber-reinforced plastic, that are
presently considered to keep the environmental regulations, require multidimensional
examination and analysis because of its heterogeneous nature a non-isotropic behavior.
Consequently, this research aims to improve the knowledge on specific lightweight material and
to contribute the confidence that toward their use in spite of its poor nature and suspicious to fail,
focusing on some fundamental material properties, such as interlaminar and intralaminar
behaviors. The research started from failure characteristics and mechanisms, followed by the
analysis of the modifications adopted to enhance its structural properties in advanced level, and
finally report the adopted experimental characterization procedures and discuss the main
findings.
The first part of the study has been focused on composite materials with special targets of
enhancement and the structural behavior of these materials was experimentally characterized.
The material was manufactured with a plain-woven S-glass fiber-reinforce plastic. The material
modification was obtained by adding nanoparticles to the matrix; therefore a nano-modified
composite was developed by the appropriate combination of epoxy and nanoclay family
particles, Cloisite 20B. Thus, the fundamental experimental work included the effect of nanoclay,
Cloisite 20B inclusion on the mechanical behavior of a woven type glass fiber reinforced plastic
(GFRP) composite. Specifically, the study examined the effect of nanoclay, added with various
weight percentages, on the tensile, compressive strengths, and modulus of elasticity of GFRP in
both weft and warp directions. Results showed that depending on the warp and weft directions,
the inclusion of nanoclay, Cloisite 20B, altered the mechanical behavior of GFRP. The advanced
investigations focus on the interlaminar characteristics of the material. In this work, the effect of
meticulous nanoclay, Cloisite 20B, inclusion on the interlaminar fracture toughness glass fiber
reinforced plastic composite was investigated using careful experimental procedure. Afterwards
the study moved to the fracture mechanics behavior, with particular reference to the mode-I
interlaminar behavior. Tests were conducted based on a double cantilever beam (DCB) specimen
using the specific American Society of Testing Materials standard (ASTM D5528). Results
showed that the inclusion of nanoclays improved the interlaminar fracture toughness of the
GFRP composite in the range of 12.65% and 54.07% relative to pristine, with progressive
percentage increment of the nanoclays weight percentage content (from 0.5 to 2%). Therefore,
the dissemination of this experimental research results contributes to overlook a better
understanding of nanoclay fillers and their contribution to mechanical behaviors; this can lead to
a better design of novel structural composites. Moreover, it guides how Cloisite fillers contribute
to improve the delamination resistance with this special composite material having a better
retardant flame propagation property that can be relevant for some structures.
The second part dealt with lightweight materials that are intended for the vehicle /automotive
industry. The intralaminar behavior of the two types of materials, which were supplied by two
international companies, was investigated. The fundamental behavior, impact, and special
structural application studies of these two types of innovative materials were examined, once
again with particular attention toward the impact response and the fracture nature of these
materials. The first material type is semi impregnated micro sandwich structure (SIMS) and it is
manufactured with two specific reinforcing fibers (carbon and glass). The other material belongs
to the glass mat thermoplastic (GMT) family that has also two types: the conventional GMT and
the GMT modified by adding unidirectional fibers (GMT-UD) to stiff the structure. For those
materials, the intralaminar fracture and the nature of the crack behavior were experimentally
investigated using compact tension specimen test. The intralaminar fracture toughness of each
material was determined along with crack propagation behavior. As a result, the output of this
research fills the gaps and it can contribute to having a full picture of the GMT and SIMS
materials.