Sandwich-type door structure for public transport applications

摘要

This thesis develops a new kind of bus door solution, where the traditional window glass has been replaced by a plastic window. The mass of the door can be significantly reduced by substituting glass with plastic. The mass reduction of the door helps making busses lighter and therefore lowers fuel consumption and emissions. Use of plastic instead of glass can also shorten delivery times. Improved impact resistance and ductility of the plastic facilitate assembly, reduce the likelihood of windows breaking and provide freedom of design. Due to the higher price, weight reduction alone is not sufficient reason for the replacement of glass with plastic. Hard-coated olycarbonate was found to be suitable window material in a previous thesis. Automotive industry has been using hard-coated polycarbonate for years in passenger cars and there are many material suppliers.Large temperature changes cause problems in structures where different materials are incorporated. Bus door is a good example of such a structure where the differences in materials thermal expansion factors must be taken into account. The prevention of thermal movement by improper methods of attachment or clearances leads to breakage or deformations in the weaker component.This thesis presents suitable methods of joining for plastics e.g. welding, adhesive bonding and mechanical joints. Some details on the welding methods, typical adhesives, sandwich theory and the use of sandwich structures are also presented.Experimental part consists of determination of the mechanical properties of production doors, sandwich and adhesive testing and two different prototype doors. First prototype is basically a production door where glass has been substituted with plastic without any other modifications to door itself. This door has been in test use for six months. From this test mainly the wear resistance of the window is evaluated. The second prototype attempts to create a new sandwich-type door structure. This thesis also presents the process leading to this prototype and other ideas under consideration.