The thesis was assigned by River Plast Oy’s Puumala’s plant. Puumala’s plant manufactures reinforced plastic doors for trailer trucks to other companies. There has been some problems with the door surface quality, because it reflects light in some parts. The CEO of the company thinks the problem would be solved by optimizing door elements.

The main goal of the thesis is to create a new structure for doors so the surface quality problems would be solved. The new structure should be as stiff as the company already uses. New structure should also be manufactured more easily.

The thesis includes making tests and simulation. Thesis included making ten tensile tests for surface lam-inate, so the modulus of elasticity of the surface laminate were solved for simulation. Second test was sin-gle-point load test for a piece of a door. The purpose of the test was to clarify mechanical properties of the door.

The information of these both tests was added to simulation part. At first, the same test piece used in sin-gle-point load test was modelled for simulation. Then the same single-point load test was simulated for that piece. This model piece was fixed so long that the simulation gave same results as the real single-point load test. This is to ensure that the model will give reliable results. New structures were designed on that model.

Four new structure options were presented to the CEO of the River Plast Oy. The CEO chose one of the op-tions, because he thinks it would fix the door surface quality problem. River Plast Oy will negotiate with the customers about the new structure option. Company will manufacture a door with the new structure option and makes some mechanical tests for it.