Mechanical Engineering MS Thesis Defense by Mr. Md Fazlay Rabbi
When: Tuesday,
November 21, 2017
10:30 AM
-
12:30 PM
Where: Textiles Building 101E
Description: Mechanical Engineering MS Thesis Defense
by Mr. Md Fazlay Rabbi
Tuesday, November 21, 2017
10:30 a.m. 12:30 p.m.
Textile Building, Room 101E
TOPIC:
High Strain Rate Response of Novel Auxetic Kevlar/Epoxy Composites and Modeling of Viscoelastic Materials Under Impact Loads
ABSTRACT:
The present study consists of two parts: (a) finding the high strain rate response of novel auxetic Kevlar/epoxy laminated composites and (b) developing a physics based model for viscoelastic materials under impact loading conditions.
A comprehensive experimental investigation was performed to study dynamic compressive constitutive response of novel auxetic Kevlar/epoxy laminated composites. Strain rate response was investigated at three different strain rates using split Hopkinson pressure bar (SHPB) test setup. Laminated composites were fabricated using vacuum infusion process. Short Nylon fibers were flocked between the laminates with different flock density and flock length. For obtaining dynamic force equilibrium in SHPB experiments, a copper pulse shaper was used to increase the rising time of incident pulse. To have comparison, woven Kevlar/epoxy composites were also characterized at same strain rates. In addition, quasi-static tests were also performed on both woven and auxetic laminated composites for completeness of the study. Woven Kevlar/epoxy composites have higher yield strength and lower percentage of elongation as compared to auxetic Kevlar/epoxy composites at similar strain rates. The failure strength of the auxetic Kevlar composites were increased almost 155% with an increase in strain rate from 1300 to 3300s-1. Furthermore, the Auxetic Kevlar composites showed a significant improvement in failure strength up to 50% compared to woven Kevlar composites at lower strain rate region.
A linear physics based model is developed to investigate the one dimensional impact on a viscoelastic material. Generalized model with three Maxwell elements were considered to describe the viscoelastic material. An analytical method based on Laplace transformation was used to solve the impact problem. To have a comprehensive understanding, drop weight impact was also considered in this study. Reduction of the impact force as well as greater energy absorption can be achieved with the increase of the loss tangent of viscoelastic material. Moreover, high stiff material absorbs more impact energy and experiences high impact force as compared to low stiff material.
ADVISOR:
Dr. Vijaya B. Chalivendra, Professor
Department of Mechanical Engineering, UMass Dartmouth
COMMITTEE MEMBERS:
Dr. Jun Li, Assistant Professor, Department of Mechanical Engineering
Dr. Yong K. Kim, Chancellor Professor, Department of Bio Engineering
Open to the public. All MNE students are encouraged to attend.
For more information, please contact Dr. Vijaya Chalivendra (vchalivendra@umassd.edu, 508-910-6572).
Thank you,
Sue Cunha, Administrative Assistant
scunha@umassd.edu
508-999-8492
by Mr. Md Fazlay Rabbi
Tuesday, November 21, 2017
10:30 a.m. 12:30 p.m.
Textile Building, Room 101E
TOPIC:
High Strain Rate Response of Novel Auxetic Kevlar/Epoxy Composites and Modeling of Viscoelastic Materials Under Impact Loads
ABSTRACT:
The present study consists of two parts: (a) finding the high strain rate response of novel auxetic Kevlar/epoxy laminated composites and (b) developing a physics based model for viscoelastic materials under impact loading conditions.
A comprehensive experimental investigation was performed to study dynamic compressive constitutive response of novel auxetic Kevlar/epoxy laminated composites. Strain rate response was investigated at three different strain rates using split Hopkinson pressure bar (SHPB) test setup. Laminated composites were fabricated using vacuum infusion process. Short Nylon fibers were flocked between the laminates with different flock density and flock length. For obtaining dynamic force equilibrium in SHPB experiments, a copper pulse shaper was used to increase the rising time of incident pulse. To have comparison, woven Kevlar/epoxy composites were also characterized at same strain rates. In addition, quasi-static tests were also performed on both woven and auxetic laminated composites for completeness of the study. Woven Kevlar/epoxy composites have higher yield strength and lower percentage of elongation as compared to auxetic Kevlar/epoxy composites at similar strain rates. The failure strength of the auxetic Kevlar composites were increased almost 155% with an increase in strain rate from 1300 to 3300s-1. Furthermore, the Auxetic Kevlar composites showed a significant improvement in failure strength up to 50% compared to woven Kevlar composites at lower strain rate region.
A linear physics based model is developed to investigate the one dimensional impact on a viscoelastic material. Generalized model with three Maxwell elements were considered to describe the viscoelastic material. An analytical method based on Laplace transformation was used to solve the impact problem. To have a comprehensive understanding, drop weight impact was also considered in this study. Reduction of the impact force as well as greater energy absorption can be achieved with the increase of the loss tangent of viscoelastic material. Moreover, high stiff material absorbs more impact energy and experiences high impact force as compared to low stiff material.
ADVISOR:
Dr. Vijaya B. Chalivendra, Professor
Department of Mechanical Engineering, UMass Dartmouth
COMMITTEE MEMBERS:
Dr. Jun Li, Assistant Professor, Department of Mechanical Engineering
Dr. Yong K. Kim, Chancellor Professor, Department of Bio Engineering
Open to the public. All MNE students are encouraged to attend.
For more information, please contact Dr. Vijaya Chalivendra (vchalivendra@umassd.edu, 508-910-6572).
Thank you,
Sue Cunha, Administrative Assistant
scunha@umassd.edu
508-999-8492
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