Citation
Muhammad, Noryani
(2019)
Regression analysis framework for material selection of natural fibre-reinforced polymer composites.
Doctoral thesis, Universiti Putra Malaysia.
Abstract
Material selection is one of the important processes to the automakers in producing
and manufacturing parts for the automotive industry. The conventional material
selections tool of Multiple Criteria Decision Making (MCDM) is based mostly on
inconsistent judgement and preference subjectivity over the process selection. The
biasness through the process selection can produce unreliable final decision. By
using Statistical Package for Social Science (SPSS), it can manage quick processing,
huge volume of data and save time and cost. In this study, a regression analysis
framework is introduced to select the natural fibres (NF), polymer matrix and
composites. Simple and multiple linear regression is used to construct statistical
modelling of natural fibre reinforced polymer composite (NFRPC). In advanced
approach, stepwise regression is used to construct the best regression modelling with
significant mechanical properties that influence the performance score (PS) of the
materials. Inferential statistical methods, such as estimation, hypothesis testing and
confidence interval, are used to test the sample data of NFRPC to make a conclusion
on the final decision. In addition, Pearson coefficient of correlation (r) is used to
identify the relationship between the mechanical properties and PS. In addition,
Multicollinearity issue is resolved by calculating the Tolerance (Tol) and Variance
Inflation Factors (VIF). Three types of errors, such as mean absolute error (MAE),
mean square error (MSE) and root mean squared error (RMSE) are used to evaluate
the estimation process. All statistical measurements in stepwise regression are used
during the screening process on material selection. The ranking process will finalize
the material based on the maximum value of PS and minimum value of estimation
error. Product design specification (PDS) of hand-brake lever parking is used as a
case study to select the natural fibre, polymer matrix and the composite at the early
stage. The ideal composition of fibre loading that optimises the PDS is identified by
using analytical approach, namely the rule of mixtures (ROM), at the final stage.
The results reveal that regression modelling can assist the design engineers to identify the best material in automotive application. Tensile strength (TS) is the
significant mechanical property in the model proposed by stepwise regression to
evaluate PS. The adequacy checking on the statistical model is performed by plotting
the normal probability of regression standardized residual and normality plot.
Regression analysis on 12 types of natural fibres and 10 types of polymers matrix
shows that the top three best materials were coir, kenaf, cotton and polypropylene
(PP), polystyrene (PS), high-density polyethylene (HDPE), respectively, to
manufacture hand-brake lever parking. The estimation of density, Young’ modulus
and tensile strength in various fibre loading using simplest micromechanical model
showed kenaf/PS composite with 40% fibre loading offer better composition to
manufacture hand-brake lever parking. A well corporation between regression and
analytical approach is proven. Overall, this work can act as a guideline for the
selection of the most suitable natural fibre, polymer matrix and composite candidate
for an engineering application. This study has contributed to material selection
process field which can provide more options of method to be chosen by
practitioners especially for automotive product development application.
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