NASA is keen on advancing technologies for lightweight composite cryotanks for heavy lift vehicles for future NASA missions. Two primary challenges must be overcome to enable the use of composite tanks for these new classes of heavy launchers. One is to develop novel, microcrack-resistant, polymer matrix composite materials that will enable the manufacture of 5 to 10 meter diameter composite tanks, and the second is to develop out-of-autoclave manufacturing methods. In response, CTD is developing novel matrix materials based on toughened epoxy and benzoxazines to meet these goals and exceed the performance of current state of the art materials. The end goal of the Phase II program is to advance the material systems suitable for out-of-autoclave fabrication of very large cryotank (10 meter diameter) structures from TRL 3 to TRL 4. The proposed Phase II SBIR program will be a synergistic effort between analytical assessments of material performance requirements, material and process development, testing to assess material performance improvements and the ability to manufacture these novel materials into microcrack resistant composites laminates and cryotanks.