  Thin shell carbon fiber composites have great potential for structures that
require large recoverable deformations, high stiffness and low weight, as in
deployable space structures, biomedical devices and robotics. Despite being
astonishingly flexible in fiber direction, thin shells are highly sensitive to
off-axis loading. High sensitivity to imperfections, manufacturing limitations
and a missing in-depth mechanical understanding hinders the creation of
transversely robust shells. This paper provides crucial insights into the
factors influencing the transverse strength of ultra-thin composites using a
highly accurate manufacturing technique to produce novel thermoplastic thin-ply
(35 {\mu}m) carbon fiber-PEEK plies. The effects of fiber type, microstructure
and polymer morphology are addressed. It was found that a combination of
microstructure tuning and isothermal crystallization can achieve thin shell
composites with a 158% improved transverse performance compared to
state-of-the-art thermosets. Moreover, this work outlines the sensitivity to
all related processing conditions, highlighting the need for accurate control
of all named parameters.
