This paper presents a new concept for a 100% plastic prototype automotive door panel. This concept has the potential of providing a weight reduction of up to 40% compared to conventional steel door panels, but with equivalent performance (static strength). This innovative technology can be used for a variety of exterior automotive parts. The concept includes a composite sandwich panel combination of GFRP (glass fiber reinforced polymer), and LACTIF®, which is expanded beads foam made from PLA (polylactic acid) and developed by JSP Corporation. This GFRP+LACTIF® composite design offers the following characteristics: Excellent environmental resistance Strong adhesion Equivalent static strength (vs. conventional door panels) Design flexibility This concept also offers an alternative to conventional steel door panel systems by using unsaturated polyester material of plant origin as part of the GFRP composite.