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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, such thin shells are highly sensitive to off-axis loading. This relates to the high manufacturing complexity and sensitivity to imperfections, revealing the need for in-depth understanding and enhancement of their transverse response. This paper provides crucial insights into influencing factors of thin-shell composites’ transverse strength using a highly controllable manufacturing technique to create novel thermoplastic thin-ply (35 μm) carbon fiber-PEEK laminas. The effects of fiber type, microstructure and polymer morphology as well as their interactions, are addressed towards a drastic increase in performance. A combination of microstructure tuning and isothermal crystallization can provide thin-shell composites with a more than 150% improved transverse performance compared to the state-of-the-art. The conducted analysis reveals the sensitivity to all related processing conditions and highlights the effect of their accurate control., Composites Part B: Engineering, 261, ISSN:1359-8368, ISSN:1879-1069

In fiber reinforced composite materials, the manufacturing process induces residual stresses and distortions that decrease the mechanical performance of the structure and affect its geometry, especially in thin laminates. Multi-physics simulations were performed to assess the spring-in effect in ultra-thin composite parabolic solar reflectors. For this purpose, a resin kinetic model has been developed by means of differential scanning calorimetry experiments. The kinetic relation has been implemented into the finite element software in order to correctly predict the evolution of the composite degree of cure during the manufacturing process. Specimens were produced in an autoclave and their final geometries were measured by means of a non-contact measuring system and compared with numerical predictions, showing very good agreement.

High strain composite (HSC) shells made from carbon fiber (CF) reinforced polymers can enable considerable mass savings in deployable space structures. Minimizing the packaged volume while maintaining structural stiffness, is a key challenge in the design of HSC structures and requires accurate prediction of a structure’s behavior during folding. A major unknown in the design of such structures is the non-linear material behavior and its effects on the stress distribution in composite laminates. This paper addresses this challenge by experimentally quantifying and modelling non-linear material behavior in unidirectional CF-Polyether ether ketone (PEEK) composites and extending the investigations to laminate level by means of an extended laminate theory. It was found that fiber non-linearity has a positive effect on laminate's flexibility, especially in cross-ply laminates. Here, neutral axis shift delays the formation of high strains on the tensile side and can mitigate critical transverse tensile stresses in off-axis plies. The susceptibility of a lamina to transverse cracking, however, limits design choices and flexibility. This highlights the importance of a suitable matrix system for these composites, which offers sufficient transverse strength to cope with off-axis stresses. The findings are put into context of foldable structures by considering the design and manufacturing of a lenticular boom structure.