Damorheology: Creep-fatigue interaction in composite materials

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:5762703

Osiroff, R

The interaction mechanisms of time dependent material behavior and cyclic damage during fatigue loading of fiber reinforced composite laminates are addressed. A new term, damorheology, was coined to describe such physical behavior. The lamina was chosen as the building block and a cross ply laminate configuration was the selected test case. The chosen material system is the Radel X/T65-42 thermoplastic composite by Amoco. The fatigue performance at the lamina level is represented by the dynamic stiffness, residual strength, and fatigue life of unidirectional laminates. The time dependent behavior is represented at the lamina level by a pseudo-analog mechanical model. The thermo-rheological characterization procedure combines mechanical (creep) and thermal (dynamic mechanical analysis) techniques. The proposed rheological model provides a complete representation of the effects of temperature and stress on the viscoelastic response. The experimental investigation of unidirectional and cross ply laminates revealed that indeed there are significant changes in the time dependent response of a laminate due to fatigue loading. In turn, the viscoelastic stress redistribution is responsible for the changes in the rate of damage evolution and varying extent of damage modes. Time dependent constitutive relationships were derived for the laminate in the form of differential equations. Applying classical lamination stress analysis together with the shear lag model, the damage evolution of cross ply laminates was predicted. Based on the laminae viscoelastic and fatigue characteristics, a cyclic performance simulation code, CYPERS, was developed. The code was designed to predict the long term performance of cross ply laminates subjected to cyclic loads. The analysis and/or accompanying code have produced satisfactory predictions for a variety of situations.

• Research Organization: Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (USA)
• OSTI ID: 5762703
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
COMPOSITE MATERIALS
COMPUTERIZED SIMULATION
CREEP
FATIGUE
FIBERS
LAYERS
MATERIALS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PETROCHEMICALS
PETROLEUM PRODUCTS
POLYMERS
RESINS
RHEOLOGY
SERVICE LIFE
SIMULATION
STRESS ANALYSIS
THERMAL ANALYSIS