Firstly, I strongly suggest that you revise your thesis, "European colonial men objectified African-American women because of their race." Unless you are focused on how slavery operated during the colonial era, before the United States declared independence in 1776, your focus on colonial men will not make much sense. Also, it's important to note that slavery was not fully developed as a social and economic system in the United States until the 1790s.
The sexual objectification of black women was directly tied to the understanding, in the South, that black bodies were property and that all people with African ancestry would exist as slaves from birth to death. The experience of black women was different from that of black men who were sold on auction blocks because the value of a slave woman was usually tied to two things: her fecundity and her sex appeal. Sometimes, a prospective slave owner wanted both; in other instances, only one of these attributes mattered. Fecundity was important because a prospective slave master wanted to ensure that his investment would produce more slaves for him to put to work or sell to other masters. In this regard, black women were regarded similarly to livestock—part of their value was tied to their reproductive capability. Some slave masters had sex with their female slaves for their own pleasure, taking them as concubines, while others did so only to produce more slaves.
For your paper, I would suggest starting off with the invention of the cotton gin by Eli Whitney in 1793. It was also in this year that the United States passed its first Fugitive Slave Law, demanding that other states, even those that forbade slavery, help to forcibly return escaped slaves to their plantations. The cotton gin allowed planters to produce more cotton, due to the machine's ability to separate the seeds from the cotton, thereby eliminating that step for the slave. No longer needing to take that step, slaves could pick more cotton, which allowed planters to reap greater profits. This desire to reap more profits is directly tied to black women, who were regarded as the "producers" of additional slave labor. With more slaves, a planter could expand his plantation. A planter's greater wealth also allowed him the privilege of buying slaves who would exist not only for labor but also for his sexual pleasure.
In plantation households, some slave women served as wet nurses and caretakers, otherwise known as "mammies." The mammy figure is a trope particular to American culture, directly linked to the history of slavery. Mammy raised and fed the children of a slave owner and mistress, and she very likely did this at the expense of her own children—that is, if her children had not already been sold to another plantation. Obviously, when one is property, a person's feelings or desires are never accounted for. Black women, during the antebellum era (and even, to an extent, during the Jim Crow era), only existed to serve the needs of others, and this service usually came at the cost of some personal violation of their bodies.