Quantifying distributed damage in composites via the thermoelastic effect

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

OSTI ID:6462197

Mahoney, B J

A new approach toward quantifying transverse matrix cracking in composite laminates using the thermoelastic effect is developed. The thermoelastic effect refers to the small temperature changes that are generated in components under dynamic loading. Two models are derived, and the theoretical predictions are experimentally verified for three types of laminates. Both models include damage-induced changes in the lamina stress state and lamina coefficients of thermal expansion conduction effects, and epoxy thickness. The first model relates changes in the laminate TSA signal to changes in longitudinal laminate stiffness and Poisson's ratio. This model is based on gross simplifying assumptions and can be used on any composite laminate layup undergoing transverse matrix cracking. The second model relates TSA signal changes to longitudinal laminate stiffness, Poisson's ratio, and microcrack density for (0[sub p]90[sub q])[sub s] and (90[sub q]/0[sub p])[sub s] cross-ply laminates. Both models yield virtually identical results for the cross-ply laminates considered. A sensitivity analysis is performed on both models to quantify the effects of reasonable property variations on the normalized stiffness vs. normalized TSA signal results for the three laminates under consideration. The results for the cross-ply laminates are very insensitive, while the (+/- 45)[sub 5s] are particularly sensitive to epoxy thickness and longitudinal lamina coefficient of thermal expansion. Experiments are conducted on (0[sub 3]/90[sub 3])[sub s] and (90[sub 3]/0[sub 3])[sub s] Gl/Ep laminates and (+/- 45)[sub 5s] Gr/Ep laminates to confirm the theoretical developments of the thesis. There is a very good correlation between the theoretical predictions and experimental results for the Gl/Ep laminates.

• Research Organization: Wisconsin Univ., Madison, WI (United States)
• OSTI ID: 6462197
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
CARBON
CRACK PROPAGATION
CRACKS
DAMAGE
DYNAMIC LOADS
ELASTICITY
ELEMENTAL MINERALS
ELEMENTS
EPOXIDES
EXPANSION
GRAPHITE
MATERIALS
MATRIX MATERIALS
MECHANICAL PROPERTIES
MINERALS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POISSON RATIO
SENSITIVITY ANALYSIS
TENSILE PROPERTIES
THERMAL CONDUCTIVITY
THERMAL EXPANSION
THERMODYNAMIC PROPERTIES
THERMOELASTICITY