The mortise and tenon structure enabling lamellar carbon composites of ultra-high bending strength

•A novel approach is reported to produce carbon/carbon fiber composites of super bending strengths from nano diamonds and carbon fibers via a phase transformation by spark plasma sintering.•The unique “mortise and tenon structure” bestows the composite bulks with excellent mechanical properties.•The current composites possess the highest specific bending strength of all current high temperature structural materials reported so far.