The phrase "are mainly comprised" is not correct in standard written English.
The correct usage would be "are mainly composed of" or "mainly consist of."
Example: "The committee members are mainly composed of experts in their respective fields."
Alternatives: "are mainly made up of" or "primarily consist of."
CNNs are mainly comprised of three types of layers.
They are mainly comprised of a complex network of triangles made out of slender members.
Agro-residues are mainly comprised of complex polysaccharides that might serve as nutrients for microbial growth and production of enzymes.
The DNGD circuits developed are mainly comprised of a transistor combined with a series resistance ended by a stub.
Similarly, as presented in Figure 5, the PreK-3 level resources are mainly comprised of individual activities, with rare lesson plans and even fewer curricula.
The target bay and switchyard support structures are mainly comprised of the steel reinforced concrete building and the steel space frame.
The headline performance report says that the serious youth violence figure "is mainly comprised of robbery (64%) and GBH (26%).
Although the 20,000-strong society is mainly comprised of priests, there are also 2,000 Jesuit brothers, and almost 4,000 scholastics – or men studying for the priesthood.
Keith Fisher Oxford It is understandable that Labour's access to justice commission is mainly comprised of lawyers (Labour access to justice commission to meet formally for first time", theguardian.com, 19 January, 2016).
I was not surprised to discover that the audience was mainly comprised of white, male thirty/fortysomethings, most of whom had a firm grip on a bottle of Budweiser or Kronenbourg.
The largest community is mainly comprised of movies, entertainment, semiconductors, and broadcasting firms.
