I wouldn't worry too much. Typically doing design, you are working as part of a team (unless you work for a really small engineering group) and it won't fall entirely on you to explain to a customer the nature of a design. When they first contact with the company, the customer delegates requirements for the specifics of the design, and the project lead (in your case, the design lead) , would present how the requirements are met. They normally don't have new engineers do this. The lead is normally a more senior engineer. My job is more analysis based, calculating stress and failure rates based on a particular design. It might fall on me, sometime in the future to have to explain my work to a customer (again, there is a more senior engineer I work with who does this), but I'll cross that bridge when the time comes...