A　bistable　composite　tape-spring　(CTS)　is　designed　with　fibres　oriented　at　±45°,　which　is　stable　at　both　extended　and　coiled　configurations,　and　able　to　be　folded.　It　has　been　used　within　deployable　structures　and　systems,　and　successfully　launched　in　space.　Its　structural　stability　is　dependent　on　angle　layups,　whilst　the　theoretical　boundaries　have　not　been　released　in　detail.　We　have　investigated　the　angle　effects　on　structural　stability　of　an　antisymmetric　CTS　structure;　a　theoretical　model　was　developed　to　evaluate　the　structural　bistability　of　the　CTS,　where　minimum　strain　energy　paths　were　established　to　investigate　the　morphing　mechanics.　The　bistability　criteria　of　a　CTS　were　then　revealed　by　considering　the　fibre　angle　effects.　Both　the　theoretical　predictions　and　experimental　observations　show　good　agreement,　and　indicate　further　insight　into　the　customised　structural　bistability　design　of　the　CTS　for　deep　space　explorations.　©　The　Institution　of　Engineering　&　Technology　2025.