A method of manufacturing a composite beam structure comprising: positioning an end piece on a mandrel, wherein the end piece has an axis, an end piece outer periphery surface, and an end piece mating end, wherein the end piece includes wedge-shaped inner locking features that are formed to project outwardly from the end piece outer periphery surface at the end piece mating end and are spaced apart from one another; and positioning a composite tube on the mandrel so that the composite tube surrounds at least a portion of the end piece mating end to form a beam joint; clamping the composite tube against the end piece mating end to form wedge-shaped imprints through the composite tube, corresponding to the wedge-shaped inner locking features on the end piece mating end, wherein the wedge-shaped imprints respectively define composite tube wedge-shaped depression surfaces about a composite tube inner periphery and composite tube wedge-shaped boss surfaces about a composite tube outer periphery, and wherein the wedge-shaped inner locking features of the end piece are covered by the composite tube wedge-shaped depression surfaces; removing the composite beam structure and the mandrel from one another upon curing for thermoset or solidifying for thermoplastic composite materials, respectively; and securing an end cap to the end piece so that wedge-shaped outer locking features of the end cap are configured to abut adjacent ones of the composite tube wedge-shaped boss surfaces, wherein the wedge-shaped outer locking features are connected to one another by a collar portion of the end cap, wherein positioning the composite tube on the mandrel includes: positioning an insert over the mating end of the end piece; forming the composite tube over the mandrel and the insert; and removing the insert prior to clamping the composite tube against the end piece mating end. positioning an end piece on a mandrel, wherein the end piece has an axis, an end piece outer periphery surface, and an end piece mating end, wherein the end piece includes wedge-shaped inner locking features that are formed to project outwardly from the end piece outer periphery surface at the end piece mating end and are spaced apart from one another; and positioning a composite tube on the mandrel so that the composite tube surrounds at least a portion of the end piece mating end to form a beam joint; clamping the composite tube against the end piece mating end to form wedge-shaped imprints through the composite tube, corresponding to the wedge-shaped inner locking features on the end piece mating end, wherein the wedge-shaped imprints respectively define composite tube wedge-shaped depression surfaces about a composite tube inner periphery and composite tube wedge-shaped boss surfaces about a composite tube outer periphery, and wherein the wedge-shaped inner locking features of the end piece are covered by the composite tube wedge-shaped depression surfaces; removing the composite beam structure and the mandrel from one another upon curing for thermoset or solidifying for thermoplastic composite materials, respectively; and securing an end cap to the end piece so that wedge-shaped outer locking features of the end cap are configured to abut adjacent ones of the composite tube wedge-shaped boss surfaces, wherein the wedge-shaped outer locking features are connected to one another by a collar portion of the end cap, wherein positioning the composite tube on the mandrel includes: positioning an insert over the mating end of the end piece; forming the composite tube over the mandrel and the insert; and positioning an insert over the mating end of the end piece; forming the composite tube over the mandrel and the insert; and removing the insert prior to clamping the composite tube against the end piece mating end.