Molecular dynamics (MD) simulations under transverse shear, uniaxial compression, and pullout loading configurations are reported for multiwall carbon nanotubes (MWCNTs) with different fraction of interwall sp(3) bonds. The interwall shear coupling in MWCNTs is shown to have a strong influence on load transfer and compressive load carrying capacity. A new continuum shear-coupled-shell model is developed to predict MWCNT buckling, which agrees very well with all MD results. This work demonstrates that MWCNTs can be engineered through control of interwall sp(3) coupling to increase load transfer, buckling strength, and energy dissipation by nanotube pullout, all necessary features for good performance of nanocomposites.