We propose a simple model to describe spider orb webs. The model has a formal analytical solution when no thread elements are broken. When the radial threads are sufficiently strong compared to the spiral threads, the model is free of stress concentrations even when a few spiral threads are broken. This is in contrast with what occurs in common elastic materials. According to our model, spiders can increase the number of spiral threads to make a dense web (to catch small insects) or adjust the number of radial threads (to adapt to environmental conditions or reduce the cost of making the web) without reducing the damage tolerance of the web.

Blisters are commonly observed when an adhesive sheet is carelessly deposited on a plate. Although such blisters are usually not desired for practical applications, we show through model experiments on angular blisters how material properties can be deduced from height profile measurements. In particular the typical curvature of the crests is found proportional to an elasto-capillary length that compares the bending stiffness of the sheet with adhesion energy. In addition, the radius of the tip allows to estimate the product of this length with the thickness of the sheet. The relevance of these results to realistic random configurations is finally confirmed. arXiv:1207.2437v1 [cond-mat.soft]