Stress-wave propagation in Al2O3-epoxy mixtures

Abstract

One-dimensional shock loading, attenuation, and recompression data from gas-gun experiments on mechanical mixtures of alumina powder and epoxy were used to develop model parameters for stress-wave propagation. Specimens with 0.42, 0.34, and 0.20 volume fractions of alumina were investigated. Calculations simulating the experiments were performed using an extension of a Maxwell rate-dependent model which requires definitions of the instantaneous, equilibrium, and relaxation functions as input. Experimental observations indicated the shock-loading behavior is identifiable with the equilibrium response, and the release wave behavior is closely related to the instantaneous response. To model these effects, for negative strain rates, indicative of expansion, a relaxation time of 0.25 μs was used; this value gave agreement between the calculated and measured release wave behavior. For positive strain rates, indicative of compression, the relaxation time was permitted to decrease to 0.03 μs, which caused the shock-loading response to be dominated by the equilibrium function. Hugoniot data determined from the stress-wave profiles were compared to effective modulus calculations. This comparison suggests a strength effect which can be interpreted as an interaction between the components. Analysis using a self-consistent scheme for spherical particles shows good correlation between calculated and measured ultrasonic and Hugoniot intercept wave velocities.

The effect of orientation on the shock response of a carbon fibre–epoxy composite

“…The explosives community has long considered particulate composite systems as many modern insensitive high explosive formulations consist of explosive crystals embedded in a polymeric binder [1][2][3][4]. Other applications include potting compounds for electronics (consisting of alumina particles in epoxy) have also been studied [5][6][7]. However, a major consideration is the requirement for light-weight materials for impact resistance, both from the military (armour materials) and aerospace (foreign object damage -FOD and bird strike) communities.…”

Destruction of filled polymer targets by high-velocity impact

“…For many target and projectile materials, the parameters c 0t , c 0p , S t , and S p are found empirically and are presented, for example, in [1,5,25]. Using expressions (3.2) and (3.3), for the shock pressure p m , the particle velocities u t and u p , the density of the compressed materials ρ t and ρ p , the specific internal energies E t and E p , and the bulk strains ε t and ε p we obtain the algebraic expressions presented in [24].…”

“…For the calculation of the shock-wave parameters c 0 and S in composites consisting of two materials with known parameters c 0i and S i , approximate methods [3,5,25] have been developed. We consider a composite material consisting of an epoxy resin and an impurity (for example, Al 2 O 3 ) as a simple mixture of two components with known equations of state and mechanical characteristics.…”

The dynamic response of carbon fiber-filled polymer composites

“…Despite their widespread application, there are few reports detailing their impact (shock) and dynamic strength properties, typically limited to low shock pressures [4][5][6][7][8][9]. There have also been investigations of the dynamic response of related (such as glass-or alumina-filled) polymer composites [10][11][12][13].…”