Environmental legislation urges manufacturers to develop effective technologies to cope with obsolete products. The goal is to optimize the disassembly procedure (cost, efficiency) with emphasis on potential recycling. In this work we adopt a destructive approach to product disassembly as an alternative to reverse assembly. Specifically we investigate unsupported screwed assemblies for which the screw head is protruding. Disassembly consist of breaking this head by applying side impact. The transient forces are measured by means of an instrumented bar. Experiments were conducted on various screw diameters and materials to assess the feasibility of this process. Typical design parameters (energy, time and forces) were measured. The fracture mechanism(s) was characterized by fractographic analysis. Results are presented and potential applications of this technique to efficient disassembly are discussed. The results are integrated into the preliminary design of robotic disassembler.