Credit Structure:(3-0)3

Catalog Description:
Stress, strain, linear elasticity, finite strain elasticity, viscoelastic properties of solid polymers. Tensile and tear strength of polymers, yielding, crazing, brittle fracture, environmental stress cracking, fatigue, toughness, impact and tear. Material evaluation based on mechanical and other properties. Conception of part. Analytical design of plastic products. Process design of plastic products. Testing of products. Case studies on plastic product design.

Course Objectives:
This course is intended to cover areas related to plastics material evaluation and product design. It gives a wide background on mechanical properties of polymers, including time dependent (viscoelastic) stress-strain, creep, stress relaxation and ultimate properties with emphasis in utilization in plastics product design. It scans other properties also used for this purpose. It covers areas such as conception of part, analytical design, process - product design relationships, testing and finalization of product design. Also case studies from various industries are discussed.

Prerequisites:
None

Textbooks(s):
N.G. McCrum, C.P. Buckley, C.B. Bucknall, "Principles of Polymer Engineering", 1987.
D.V. Rosato, D.P.Di Mattia, D.V. Rosato, "Designing with Plastics and Composites, A Handbook", 1991.

Reference:
None

Syllabus:
I. Introduction to mechanical properties. Definition of Lagrangian strain, strain tensor. Large strains. Stress tensor. Relationships between stress and strain, time dependency. Concept of linear material. Generalized Hooke's law. (0.5 week)
II. Finite Strain Elasticity. Stress-strain relationships. Thermodynamic considerations.. Form of strain-energy function. Strain invariants. Particular stress-strain relations. Experimental studies of finite-elastic behavior. (1 week)
III. Viscoelastic properties of solid polmers. Phenomenology. Mathematical treatment. Measurement of viscoelastic behavior (creep, stress relaxation, dynamic mechanical experiments, wave propagation, use of WLF equation). Results of experimental studies (amorphous polymers, crystalline polymers, time-temperature equivalance). (2 weeks)
IV. Tensile and tearing strength of polymers. Yielding and crazing. Brittle strength and concept of critical stress intensity factor. Experimental K calibration curves. Fatigue tests, subcrtical crack growth, influence of stress corrosion agents and design. Environmental stress cracking. Peel strength and adhesion, relationship to Kc. Toughness of plastics. Concept of work to fracture and the effect of stress concentration. Izod, Charpy and other impact tests. Tear strength of polymers. (2 weeks)
V. Material evaluation criteria. Cost, processibility, strength and rigidity (long and short term), temperature resistance, chemical resistance, other properties. (1 week)
VI. Conception of part. Initial functional design, process selection and consideration of factors such as mold and die design, auxiliary operations etc. (1 week)
VII. Analytical design of plastic products. Strength and limitations of such analysis. (2 weeks)
VIII. Process design of the product, effects of process variables and mechanical design (gate, location, weld lines, orientation etc.) on final properties. (1 week)
IX. Testing of prototypes and final products and finalization of product design. (0.5 week)
X. Case studies: Construction sector housing, industrial; Agriculture; Packaging; Consumer products; Automotive. (3 weeks)

Homeworks, Quizzes, Projects:
A term project is given

Computer Usage:
None

Laboratory work:
None

Category Content:
Mathematics and Basic Sciences: None
Engineering Design: 1 credit
Engineering Sciences: 2 credits
Humanities & Social Sciences: None
Departmental:None

Instructors:
Ülkü Yilmazer