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Physical Results of the Mixing Processes
A good green strength (pre-compression strength) results in better handling of the compressed bodies of the friction lining. These can be conveyed dependably with the values determined from the prepress to the hot press.
A higher green strength was achieved in the mixtures with an increasing proportion of HAR wollastonite. The values of the mixtures filled with HAR wollastonite were clearly higher than those filled with mineral fibers. This was attributed to the needle structure of the wollastonite. The HAR wollastonite needles obviously formed a braid with a higher degree of stability.
Figure 11 shows that there is no significant difference in bulk volume between the various recipes.
Physical Results of the Pads
The compressed disk brake pads were formed completely after compression and grinding, without any flaws. The entire surface of the pads was thereupon sheared off in the testing machine by means of a shearing cutter. The shear strength values obtained and, with inclusion of the pad surface, the specific shear strengths result from this.
Figure 12 shows that the shear strengths of the mixtures with HAR wollastonite were greater than those of the pads containing mineral fibers. However, a decrease in shear strengths with an increasing proportion of HAR wollastonite can be detected in this case. The strength advantage of HAR wollastonite in comparison to mineral fibers is particularly clear when recipes 1 and 3 with the same proportions of magnesium carbonate are compared directly.
Fig. 11 Bulk volume and pre-compression strength of the various recipes
Fig. 12 Shear strength of the recipes investigated
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