Complex engineered systems design is a collaborative activity. To design a system, experts from the relevant disciplines must work together to create the best overall system from their individual components. This situation is analogous to a multiagent system in which agents solve individual parts of a larger problem. Current multiagent models of design teams, however, do not capture this distributed aspect of design teams--instead representing designers as agents which control all variables of the problem. This paper presents a new model of design which captures the distributed nature of complex systems design by decomposing the ability to control variables of the design to individual computational designers acting on a design problem with shared constraints. These designers are represented as a multiagent learning system which is shown in this paper to perform similarly to a centralized optimization algorithm on the same domain. When used as a model, this multiagent system is shown to perform better when the level of designer exploration is not decayed but is instead controlled based on the increase of design knowledge, suggesting that designers in multidisciplinary teams should not simply reduce the scope of design exploration over time, but should adapt based on changes in their collective knowledge of the design space to achieve the best design outcome. This multiagent system is further shown to produce better-performing designs when computational designers design collaboratively as opposed to independently, confirming the importance of collaboration across disciplinary boundaries in complex systems design.