Simplified estimation method for envelope curve of wrinkled membrane surface distortions

Structural components such as those of inflatable antenna reflectors, solar sails, and sun shields are made of membranes. Although the membranes have the suitable mechanical properties that aid their use in constructing such structures, they are still faced with various challenges in ensuring the safety, reliability, and durability of the structures.

Most membranes are incapable of overcoming compressive loading due to their almost negligible bending stiffness. As a result, the membrane structures undergo buckling effects which leads to the development of wrinkles on their surfaces. These wrinkles have contributed to massive failures of such structures in the long run. With the future structures expected to be more reliable, efficient and long-lasting, it will be a good idea to incorporate a strategy that is capable of accurately predicting the formation and development of the wrinkles thereby helping in the design and building of structures.

Professor Takashi Iwasa at Tottori University in Japan proposed a more straightforward and experimental structure method for estimating an envelope curve of wrinkled-membrane surface distortions. He aimed at improving the current techniques used which have been ineffective and unreliable in most cases. The research work is currently published in the journal, Thin-Walled Structures.

Professor Iwasa commenced his experimental work by developing a formula for calculating the envelope curves of the membranes whose surfaces have been wrinkled due to the compressive loadings. He took into considerations the physical factors that affect the membrane wrinkles such as the principal strain in the region, the in-plane strain of the region and the length of the wrinkle line. In the experiment, the membrane model was subjected to shear loading from the upper edges and tension at the corners. The wrinkles that apparated on the surfaces of the membranes were measured using photogrammetry technique before analysis by the finite element analysis method.

Irrespective of the various methods by which the wrinkles were formed on the membranes surfaces, the author successfully estimated the envelope curves profiles of the wrinkles on the membrane surfaces. The mutual agreement between the estimated results and those of the experimental results further confirmed the validity of this proposed estimation method.

According to Professor Takashi Iwasa, the proposed formula is less cumbersome as compared to the previous estimation methods which majorly relied on the computational approaches. This proposed method takes into consideration the various physical quantities that affect the behaviors of the wrinkles which can be represented as two-dimensional problem hence making the analysis less complicated.

The practical method proposed by Professor Iwasa is expected to advance the design and building of the future membrane incorporated structures. This is because the method itself is cheap concerning analysis computations and time required for the same.