Abstract: An impact resistant structure is described which comprises a substantially sinusoidally shaped elastically collapsible open-celled fluted layer disposed between but not bonded to constraining layers, whereby in an impact event, the flutes are free to move between the constraining layers and stress concentrations in the collapsing flutes immediately beneath the impacting object are minimized by the absorption of impact forces by neighboring flutes that resiliently collapse in an accordion-like fashion, and return substantially to the original shape after impact without permanent damage to the structure.