Optimal design of laminated composited under cryogenics

Dissertant

Fayd Allah, Majid Habib

University

University of Technology

Faculty

Department of Mechanics and Equipments Engineering

University Country

Iraq

Degree

Ph.D.

Degree Date

2006

English Abstract

The spaceship structures and some kinds of robotics made of composite I materials are exposed to static and dynamic stresses under very low temperatures especially while leaving the outer atmosphere.

The graphite / epoxy such as Polymer-Enhanced, Graphite Reinforced Cementations (PEGRC) composite materials, is one of the main composite materials used in the aerospace structures and robotics.

This thesis has studied the experimental, analytical and numerical solutions for the optimal design of those laminate composite materials under the mechanical and thermal stress conditions.

The experimental program includes design and manufacturing of two experimental devices (not available in Iraq).

These devices are; the tensile standard cooling device and bending fatigue standard cooling device.

Standard laminate specimens of (PEGRC) composite materials with difference in aspect ratios, thicknesses and ply angles of graphite fibers are manufactured.

More than (1000) standard specimens are used in this research.

It is noted that a new modified epoxy which resists cracks under very low temperatures has been produced in this research.

The cooling process is done by using nitrogen and helium liquids at steady state and constant pressure to achieve a wide low range of temperatures from (25 °C) to (-269 °C) for the experimental standard specimens which are exposed to static or dynamic loading.

The mechanical and thermal properties of the composite materials were investigated in this thesis through the static tests of the standard specimens under low temperatures by using strain gauges technique.

This thesis includes manufacturing plates of (PEGRC) composite materials according to the optimal dimensions done in ANSYS (5.4) program, then a series of mechanical tests and calibrations are done to find out their fcoriformity to the testing standards The maximum deflection of optimal plates will be obtained experimentally under cryogenic temperature of (-269 °C).

The dynamic characteristics of optimal (PEGRC) composite plate experimentally were achieved (by using five different specimens in aspect ratios land thicknesses) and exposed to (-269 °C).

These specimens are exposed to impact hammer transducer in order to obtain frequencies and mode shapes for these plates A numerical investigation on the laminates in an ANSYS (5.4) program using finite element method, was achieved by inserting mechanical and thermal properties of the (PEGRC) composite materials which were obtained from the experimental tests, in order to have optimal aspect ratios, thicknesses and ply angles of graphite fibers.

The dynamic characteristics of the same optimal (PEGRC) plates are done numerically by using ANSYS (5.4) program and analytically by using FORTRAN (90) program.

In comparing the results of mechanical and thermal properties for the used composite materials obtained experimentally with those of reference [23], the error rates in results are 8.7 %, 5.7 %, 9.1 %, 5.1 %, 6.9 % and 8% of values CL \, a2, Eh E2, G!2, and u12, respectively.

And in comparing the numerical results of (PEGRC) laminated composite of optimal aspect ratios, thicknesses and ply angles of graphite fibers at different low temperatures that are obtained from ANSYS (5.4) program.

There is a close agreement in results in terms of experimental, numerical and analytical and dynamic characteristics of plates under cryogenic temperature (-269 °C).

Main Subjects

Mechanical Engineering

Topics

• Air conditioning

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305877