The mechanical behaviour of the covering materials of greenhouses may be assessed by means of conventional and specific testing methods . No standard methods exist for testing the mechanical and physical properties of flexible and rigid plastics and glass to be used as covering materials of greenhouses in the European Union (EU) . Some of these properties , are rather specific for greenhouse applications and cannot be measured properly with existing testing methods .
This situation becomes even more complicated because of the dif ferent requirements and climatic conditions of the various EU regions . This paper provides a systematic presentation of the mechanical properties measured by existing ''general purpose'' methods as well as specific testing methods included in national and international standards . The values presented are found to vary considerably for the same material and they also dif fer between the dif ferent materials considered , with the dif ference depending on the testing method used . In general , technical information regarding the mechanical properties of materials used as coverings of greenhouses is neither available nor warranted in a systematic way with a few exceptions .
This work is intended to improve the current knowledge for accessing and defining the quality criteria for evaluating the variety of greenhouse covering materials encountered in EU countries .