Structural analysis and strength-to-weight optimization of wood-based sandwich composite with honeycomb core under three-point flexural test

Wood-based sandwich composite with a paper honeycomb core, especially for thick boards, has the advantage of high strength-to-weight ratio for the use in lightweight furniture products, interior walls etc. Employing both theoretical and experimental methods, this study investigated the influencing factors of various failure modes and its transition to obtain optimized structural parameters after a quasi-static load was applied. The results reveal that the skins of MDF are too strong for the paper honeycomb core. Both failure modes are caused by weak core properties. If the thickness or strength of the skins could be reduced or the core strength could be reinforced, then optimal failure mode of simultaneous core and skin failure could be reached. The intersection point of three transition lines is the best combination of structural parameters, meaning highest strength-to-weight ratio. At this point, failure of core shear, indentation and face fracture occurs simultaneously. The distance from a structural parameter to intersection is an effective index to express the degree of optimization for the strength-to-weight ratio of composites. Specimens close to the intersection point have optimal structural parameters and high strength-to-weight ratio. On application level, the optimum strength-to-weight ratio could be obtained easily by adjusting the surface or core thickness, if the materials were fixed first.