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Thesis (M.Sc.) Master Egypt - Japan University of Science and Technology (E - JUST) - School of Innovative Design Engineering - Materials Science and Engineering Department 2024

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Glass Fiber Reinforced Polymers (GFRPs) , a type of Polymer Matrix Composites , are notably used in the automotive and aerospace industries due to their lightweight , strength , and energy absorption compared to unreinforced polymers and conventional metals However , structures made from these materials are susceptible to significant impact loads under diverse operating conditions In structural conditions , GFRPs can experience various external loadings leading to different types of failures , such as matrix cracking , fiber failure , and delamination These failures can result from factors such as the type of fiber and matrix , the percentage of fibers in the matrix , ply angles , and the overall stacking configuration This research aims to study the effect of stacking sequence on the high strain rate (HSR) mechanical properties of GFRPs using both finite element method (FEM) and experimental approaches Experimental studies were conducted to verify the accuracy of the FE model The study began with the manufacturing of [0°/90°] 16-ply layered bi-directional GFRP laminates using a bi-directional E-glass embedded in a Kemapoxy RGL epoxy matrix , employing the Vacuum Assisted Resin Transfer Moulding (VARTM) manufacturing process These laminates were then examined for their high strain rate impact properties using the Split Hopkinson Pressure Bar (SHPB) testing apparatus The SHPB samples were tested at 0.5 bar , 0.7 bar , and 0.8 bar pressure Subsequently , a validation numerical model was created in ABAQUS/CAE software , accurately reproducing the SHPB experimental testing conditions , including the striker , incident , transmitted bars , and the specimen The model was run at velocities of 7 m/s, 12.8 m/s, and 17 m/s. The results showed close correlation between the experimental and numerical model results , with an average of 0.38% difference in compressive strength and 9.2% in the energy absorption respectively The slight differences can be attributed to experimental conditions such as geometrical accuracy , bonding quality between the strain gauges , and signal loss due to wiring connections during testing Further , a specimen geometrical model was designed for four different stacking sequences of the GFRP : unidirectional [0], bi-directional [0°/90°]ns, angle-ply [+45] , and quasi-isotropic [(0/+45°/90°)] laminates. The GFRP material specimen was created using an orthotropic elastic material model , and the damage parameters were determined using the Hashin damage model The striker bar was shot at impact velocities ranging from 7 m/s to 18.3 m/s , corresponding to the strain rates of 1482 s¹ to 3964 s¹ The results indicated that the quasi- isotropic stacking sequence has the most favorable mechanical properties at high strain rate , which can be attributed to the arrangement of layers that alternates between 0°, +45° and 90° ii which provides excellent strength for structural purposes The compressive strength showed an increase from 313.36 MPa to 761.73 MPa when the strain rates varied between 1482 s¹ and 3964 s. Additionally , there was an increase in the energy absorption of about 82% for the QI stacking sequence when the impact velocities rose from 7 m/s to 18.3 m/s. The results have shown the importance of the stacking sequence and strain rate on the dynamic characteristics of this composite material The simulation results provide valuable insights for the future development and application of GFRP composites under impact loading circumstances

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(IDE) School of Innovative Design Engineering (MSE) Materials Science Engineering