Thorat, Satish Prakash and M, Ramji
(2018)
Study of interaction effect between a line inclusion
and a hole using Digital Photoelasticity.
Masters thesis, Indian Institute of Technology Hyderabad.
Abstract
The ease of fabrication and superior mechanical properties has emerged the new application areas
for short-�bre-reinforced-polymers (SFRP). These SFRP has a new range of performance capabil-
ities and is designed to �ll the property gap between polymers and sophisticated continuous-�bre-
reinforced-polymers (CFRP). Increased applications of composite materials have also increased the
need of defects studies and e�ect of these defects on their mechanical and other properties too.
The most common and much intense defect observed in the composite materials is porosity, the
presence of voids in the matrix phase. The void content is the potentially harmful defect in the
composite materials and can signi�cantly a�ect the mechanical properties. In case of SFRPs, �bre
end singularity problems are often modelled and studied as �bres as inclusions where the focus is on
�nding fracture parameters like stress intensity factor. The present study is devoted to exploring the
e�ect of void on the fracture properties, in case of SFRPs. This problem is studied for the simplest
form where the voids are modelled for the 2D case, i.e. a circular hole near the �bre. Hence the
problem solved is a rigid line inclusion(indicates �bres) with a hole(indicates 2D voids) embedded
in a matrix-resin. There are two reasons for modelling the �bre as a rigid line inclusion. First is
the thickness of the steel inclusion, that we have used, is very small compared to other specimen
dimensions. Second is the strength of the steel is very high compared to the strength of matrix-resin
which is such true case in SFRP where �bre has more strength than that of the matrix material.
Instead of stress intensity factor, strain intensity factor is used for quantifying the singularities at
the tip of the inclusion because it is more appropriate to use in case of inclusion problems. Further,
the variation of strain intensity factor with respect to three parameters, namely diameter of a hole,
length of line inclusion and the distance between the inclusion and a hole is studied. We have used
a numerical methodology, based on the reciprocal theorem, to calculate the strain intensity factor of
the inclusion in the �nite geometry. The input to this method is the actual elasticity solution, which
is obtained using �nite element analysis (FEA). Furthermore, these FEA models are validated using
the experimental technique, Digital Photoelasticity, qualitatively and quantitatively as well.
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