Inelastic behavior of thermoplastic composites

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6468678

Chung, I

The mechanical behaviors of AS4 reinforced PEKK-based composites were studied. These new thermoplastic composite systems developed by Du Pont exhibit pronounced nonlinear and time dependent behaviors. To characterize the inelastic behavior, classical plasticity and creep theory have been adopted and modified for the orthotropic case by using a one-parameter potential function. The elastic-plastic behavior of LDF(TM) AS-4/PEKK system employing aligned, long discontinuous fiber reinforced composites has been studied in comparison with the continuous fiber reinforced counterpart. A dual mode plastic potential action was employed to model the plastic behaviors of these composites at room and elevated temperatures up to 177 C. A one-parameter failure criterion was also applied to predict the failure strength. Off-axis coupon specimens were used to measure the failure strength and generate stress-strain curves from which the elastic-plastic properties were extracted. It was observed that the elastic-plastic performance and strength of LDF(TM) are as good as those of the continuous fiber system. The material constants were determined by using uniaxial creep tests of off-axis coupon specimens. In terms of effective stress and effective creep strain, the anisotropic creep behavior was described by a stress dependent master creep curve irrespective of loading direction relative to fiber orientation. This model was implemented into classical laminate theory to predict the creep behavior of composite laminate, and compared with experimental data of (+/- 45)4s laminate specimens. The influence of thermal stress was included. The micromechanical approach also was tried to model the inelastic behavior of continuous fiber reinforced composites. The fiber was assumed to be orthotropically elastic, and the matrix to conform to the classical elastic-plasticity and creep theories.

• Research Organization: Purdue Univ., Lafayette, IN (United States)
• OSTI ID: 6468678
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
COMPOSITE MATERIALS
CREEP
ELASTICITY
FIBERS
MATERIALS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PERFORMANCE
PETROCHEMICALS
PETROLEUM PRODUCTS
PLASTICS
POLYMERS
REINFORCED MATERIALS
REINFORCED PLASTICS
RESINS
STRESSES
SYNTHETIC MATERIALS
TENSILE PROPERTIES
THERMAL STRESSES
THERMOPLASTICS