Stress Pulse Attenuation in Cloth-Laminate Quartz Phenolic

Abstract

Using flat plate impact techniques and quartz stress gages, a study of the propagation of short-duration stress pulses in a cloth-laminate quartz phenolic composite was made. Propagation characteristics, wave shape and peak stress attenuation, were measured for 14.5 and 7 kbar initial impact stresses and 0.1, 0.2, and 0.3 μsec initial pulse durations for propagation distances up to 52 times the impactor thickness. The experimental results showed marked dispersive spreading of the wave profiles and very strong attenuation of stress, but no evidence of elastic-plastic effects. The amount of attenuation was much greater than could be attributed to "normal" atten uation in homogeneous materials with a modulus equivalent to the com posite modulus. Experimental results were compared to calculations based on a rate dependent analogy using a generalized Maxwell model. The instantaneous and equilibrium response of the model was defined solely in terms of bulk properties of the components of the composite; while a single relaxation time of 0.023 μsec was determined from experiment. Model predictions agreed extremely well with the measured profiles, giving ± 10% agreement to the measured half-amplitude wave velocities. Attenuation was predicted to better than 20% in stress, which is quite good. Quantitative agreement was found between calculations and the measured results of other investigations, as well.