will my defaulted student loan affect my affidavit of support?

The fact that you have defaulted on your student loans does not affect your ability to file an affidavit of support. You will need to demonstarte you have sufficient income and/or assets to meet the requirements. If you do not have sufficient income or assets, you will need a joint sponsor. You read more about the affidavit of support by clicking Affidavit of Support.