Abstract-Differences in texture and discovery location prompted us to analyze 16 irons from Morasko; one from Seel€ asgen, known to have a similar composition; and a new mass found at Jankowo Dolne. These were analyzed in duplicate by instrumental neutronactivation analysis (INAA). The results show that all 18 samples have very similar compositions, distinct from all other IAB irons except Burgavli; we conclude that they are all from a single shower. Eight of the samples were from regions with large amounts of cohenite (but were largely free of inclusions) and six were from samples with very little cohenite; we could find no resolvable difference in composition between these sets, a fact that suggests that the C contents of the metal phases were similar in the two areas. Although Morasko has been classified into the IAB main group (IAB-MG), its Ir plots well outside the main group field on an Ir-Au diagram. We considered the possibility that the low Ir reflected contamination by a melt from a IAB region that ponded and experienced fractional crystallization; however, because Morasko has Pt, W, and Ga values that are the same as the highest values in IAB-MG, we rejected this model. We therefore conclude that Morasko formed from a different melt than the IAB-MG irons; the Morasko melt was produced by impact heating, but one or more of the main Ir carriers did not melt, leaving much of the Ir in the unmelted residue. Copper is the only element that shows resolvable differences among Morasko samples. Most (13 of 18) samples have 149 AE 4 lg g À1 Cu, but three have 213 AE 10 lg g À1

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Acoustic emission (AE) was applied for detection of microcrack initiation in carbon fiber reinforced polymer composites subjected to shear stresses. Experimental materials were prepared from polyester bonded unidirectional (1D) non-crimp fabric and 2D plain-weave carbon fiber fabrics, using the resin transfer moulding technology. Control of epoxy resin/carbon textile proportions enabled variation of fiber volume content from small (34/35% for 2D/1D), through medium (51%) to high (68%). Rectangular samples (45 × 4 × 2 mm) were cut from 1D plates along [0] and across [90] fibers. Similar size samples from 2D plates were cut along warp/weft axes as well as in two orthogonal bias directions. Selected side surfaces were polished for microscopic (SEM) observations. Short-beam-strength tests were performed in 3-point bending (l/h=4), with two AE sensors attached for damage monitoring, which allowed to interrupt loading sequence before final failure. The acoustic emission historic index was the most effective AE parameter in damage initiation control. Microcracks developing on polished composite side-surfaces were observed under the SEM and direct microscopic evidence confirmed fiber debonding to be the principal mechanism of crack initiation in these materials and testing conditions before any further damage.

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The aim of the study was to describe the structure of composites based on the AlSi7Mg2Sr0.03 alloy matrix reinforced with SiC particles added in an amount of 10% and with a mixture of SiC and GR particles added in a total amount of 20%. Studies of the composite structure, were carried out by scanning electron microscopy (SEM). Based on the results of chemical analysis in microregions, an increased content of elements such as Mg, O and Si and of the precipitates was observed at the interface. In many places in the examined sample, GR particles formed partly disintegrated conglomerates with well developed boundaries. The effect of the content of particles of the reinforcing phase on the functional properties of the composite was investigated during studies of abrasion. The lowest mass loss of 5,33mg was obtained for the AlSi7Mg2Sr0.03 alloy reinforced with 10% SiC particles.