Abstract: An instrument can be receivable in a coupler of a surgical arm. The instrument can include a stem, coupler, and a retractor blade. The stem can include a proximal portion couplable to a coupler, and can include an opposite distal portion. The retractor blade can be couplable to the coupler via a mating feature.

Abstract: A fiber preform made of carbon fibers is densified with a carbon matrix in a plurality of separate stages. After a first densification stage and before the end of carbon matrix densification, ceramic particles are introduced in order to be dispersed within the composite material part. The introduced particles have a mean size of less than 250 nm and are made at least of a ceramic compound of an element selected from titanium, yttrium, tantalum, and hafnium, the ceramic compound being selected from oxides, nitrides, and mixed oxide, carbide, and/or nitride compounds that do not react with carbon at a temperature of less than 1000° C. and that have a melting point higher than 1800° C.