Youth Centre of Scienceand Technology, Moscow, Russia(Received January 3, 2001)(Accepted in revised form February 15, 2001)Keywords: Assembly of interlocked tetrahedrons; Structural behaviour; Mechanical properties;Toughness; CompositesIntroductionIn this communication we propose a new material architecture based on regular assemblies of identicalinterlocked elements. The packing arrangement is such that each individual element is prevented frombreaking out by its immediate neighbours. It is claimed that the existence of such interlocked assembliesopens up a new direction for creating special strong and flexible composite materials with high impactresistance.In conventional composites, the reinforcement particles are held together by a matrix or a binderphase. Consequently, the overall strength is restricted by the strength of the matrix no matter how strongthe particles are.In principle, the strength of a composite could be increased if the particles were directly connectedto each other. In this case, the matrix or the binder phase would only play the role of a ‘buffer’,inhibiting the propagation of dislocations or cracks from one particle to another. The matrix could alsoprovide additional properties, such as thermal or acoustic insulation.Interlocking can, of course, be achieved by equipping reinforcement particles or building blocks withspecial locking ‘keys’ (this is particularly the case in the building industry, cf., e.g., self-locking bricks).Obviously, the ‘keys’ are stress concentrators that impose severe limitations on the overall strength ofthe structure, not to mention the additional technological difficulties associated with the manufacturingof blocks with ‘keys’. We propose a different approach to the production of interlocked structures. Itis based on the use of the topological possibility of establishing self-locking in assemblies of simpleconvex shaped elements free of stress concentrators. In what follows, a particular example of aninterlocked layer structure consisting of identical tetrahedron-shaped elements packed in a special wayis discussed. The first results of mechanical tests done on an experimental specimen assembledaccording to this recipe are then presented. Finally, a brief outlook on new perspectives resulting fromthis novel approach to materials design is given.