Shatter free shell body for warhead : Concept study

Abstract: Future warheads face not only performance-, environmental- and environmental resistance requirements but are also facing requirements to reduce collateral damage on impact. This report is a concept study on the development of shatter free shell bodies for warheads carried out at Saab Dynamics AB. Focus of the concept study was identifying alternative materials for use in the warhead casing, identifying manufacturing processes useable in the production of casings of selected materials, identifying possible suppliers both in Sweden and abroad, as well as calculating an indication of manufacturing cost for both prototype and series manufacturing. A pre-study was carried out before initiating the concept study, studying earlier research performed within the field and retrieving basic knowledge of warhead component configuration and functionality, followed by establishing a requirement specification to be used for evaluation purposes during the concept study. Concept study material evaluation concluded the use of a fibre strengthened polymer matrix composites to achieve desired final properties of the component. Important factors for alternative materials ability to achieve required mechanical properties were found to be the need for high fibre volume content, long fibre reinforcements as well as the need for possibility of orienting fibre direction in order to accommodate applied stresses. An evaluation was executed of applicable manufacturing methods ability to attain good values of selected material factors, derived from the material evaluation; as well as an assessment of set methods repeatability, potential for automation and relative laminate quality. Combined with estimation of prime and sales cost resulted in the recommended use of filament winding using a thermoset polymer matrix. Combining process factors of the selected manufacturing method with remaining material alternatives resulted in further delimitation of materials and a final material recommendation. Subsequently threading integrity was evaluated for selected concept solution due to that only unfavourable fibre orientation in the section being possible. This resulted in the need of minor dimension changes to avoid stripping of threads during firing sequence. Estimated required dimensional change was assessed as acceptable but would however need be evaluated in future development. Final recommendation for future development is to commence testing of shell body composed of filament winded carbon epoxy composite. Estimated required dimensional changes is an increase slipping groove radius from 0,3 mm to 1,5 mm and an increase of thread length by 6 mm.