“…Since then, rotation-free IGA shells have been steadily advanced, for example to PHT-splines (Nguyen-Thanh et al, 2011), anisotropic materials (Nagy et al, 2013), damage (Deng et al, 2015), biological materials (Tepole et al, 2015), fracture (Kiendl et al, 2016), liquid shells , elasto-plasticity (Ambati et al, 2018), phase separation (Zimmermann et al, 2019), thermo-mechanical coupling (Vu-Bac et al, 2019), multi-patch constraints (e.g. see the recent review in Paul et al Paul et al (2020)), and reduced quadrature (Zou et al, 2021). Balobanov et al Balobanov et al (2019) present a general strain gradient theory and its corresponding isogeometric finite element formulation for Kirchhoff-Love shells.…”