In this paper we describe our measurements of the Weibull parameters of a specific basalt material, called Yakuno basalt, which was used in documented high‐velocity impact experiments. The outcomes of these experiments have been widely used to validate numerical codes of fragmentation developed in the context of planetary science. However, the distribution of incipient flaws in the targets, usually characterized by the Weibull parameters, has generally been implemented in the codes with values allowing to match the experimental outcomes; hence the validity of numerical simulations remains to be assessed with the actual values of these parameters from laboratory measurements. Here we follow the original method proposed by Weibull in 1939 to measure these parameters for this Yakuno basalt. We obtain a value of the Weibull modulus (also called shape parameter) m in the range 15–17 with a typical error of about 1.0 for each different trial. This value is larger than the one corresponding to simulation fits to the experimental data, generally around 9.5. The characteristic strength, which corresponds to 63.2% of failure of a sample of similar specimens and which defines the second Weibull or scale parameter, is estimated to be 19.3–19.4 MPa with a typical error of about 0.05 MPa. This parameter seems to not be sensitive to the different loading rates used to make the measurements. A complete database of impact experiments on basalt targets, including both the important initial target parameters and the detailed outcome of their disruptions, is now at the disposal of numerical codes of fragmentation for validity test.

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Porous structure is common in the asteroids and satellites of the outer planets. In order to study the relationship between the structure of small bodies and their thermal and collisional evolution, we performed impact disruption experiments on porous sintered targets using a light-gas gun at velocities ranging from 10 to 100 m/s. The sintered glass bead targets were prepared to have roughly the same porosity but with different compressive strengths, ranging over an order of magnitude, by controlling sintering duration and temperature. The results of the impact experiments show that the targets of higher compressive strength have higher impact strengths. However, compared to previous results on impact disruption of porous sintered targets with a collisional velocity of approximately 6 km/s, the values of impact strength in this study were found to be lower by an order of magnitude.

[1] Small icy bodies in the outer solar system have been shown to consist of ice-silicate mixtures. The results of previous impact cratering experiments on ice-silicate mixture targets showed that a crater volume decreases with increasing silicate content. Surface strength controls craterings in laboratory experiments and on small bodies with a certain degree of strength. In this study we measured the uniaxial compressive and tensile strength of the targets used in previous impact cratering experiments by uniaxial compression and Brazilian tests, respectively, at 263 K and calculated the shear strength from the measured values. We found the uniaxial compressive and tensile strength increased with silicate content, which explains why the crater volume decreases with increasing silicate content. Since the gradient of increase of the uniaxial compressive and the tensile strength was different, the difference between the tensile strength and the uniaxial compressive strength becomes smaller with the increase of silicate content up to 50 wt %. We show that the crater spall diameter is better scaled by the tensile strength to compensate the difference of the silicate content than by the uniaxial compressive strength.Citation: Hiraoka, K., M. Arakawa, M. Setoh, and A. M. Nakamura (2008), Measurements of target compressive and tensile strength for application to impact cratering on ice-silicate mixtures,