Composite elements made of two plastics layers connected to one another by way of a core layer made of isocyanate-based foam, where the envelope density of the foam in accordance with DIN 53420 is from 90 to 350 kg/m 3 and the foam is obtainable from the reaction of the components consisting of A) a polyol component consisting of a) from 0 to 25% by weight, preferably from 2 to 8% by weight, based on the total quantity of isocyanate-reactive constituents of component A), of isocyanate-reactive short-chain polyols and/or polyamines and/or polyhydroxyamines with molar mass from 90 to 350 g/mol, preferably from 200 to 300 g/mol, and with functionality from 2 to 6, b) from 0.1 to 25% by weight, preferably from 1 to 5% by weight, based on the total quantity of component A), of polyhydrazocarbonamide particles or polyurea and polyhydrazocarbonamide particles, c) from 50 to 90% by weight, based on the total quantity of the isocyanate-reactive constituents of component A), of isocyanate-reactive polyether polyols and optionally polyester polyols with equivalent weights from 500 to 5000 g/mol, preferably from 900 to 2200 g/mol, and functionalities from 2 to 6, d) catalysts, e) blowing agents, f) optionally auxiliaries and additives and B) an isocyanate component with from 20 to 33% by weight content of isocyanate groups, preferably from 25 to 33% by weight, where the ratio of the number of the NCO groups of component B) to the number of the groups of component A) that react with NCO groups is from 0.7:1 to 1.2:1. A) a polyol component consisting of a) from 0 to 25% by weight, preferably from 2 to 8% by weight, based on the total quantity of isocyanate-reactive constituents of component A), of isocyanate-reactive short-chain polyols and/or polyamines and/or polyhydroxyamines with molar mass from 90 to 350 g/mol, preferably from 200 to 300 g/mol, and with functionality from 2 to 6, b) from 0.1 to 25% by weight, preferably from 1 to 5% by weight, based on the total quantity of component A), of polyhydrazocarbonamide particles or polyurea and polyhydrazocarbonamide particles, c) from 50 to 90% by weight, based on the total quantity of the isocyanate-reactive constituents of component A), of isocyanate-reactive polyether polyols and optionally polyester polyols with equivalent weights from 500 to 5000 g/mol, preferably from 900 to 2200 g/mol, and functionalities from 2 to 6, d) catalysts, e) blowing agents, f) optionally auxiliaries and additives and a) from 0 to 25% by weight, preferably from 2 to 8% by weight, based on the total quantity of isocyanate-reactive constituents of component A), of isocyanate-reactive short-chain polyols and/or polyamines and/or polyhydroxyamines with molar mass from 90 to 350 g/mol, preferably from 200 to 300 g/mol, and with functionality from 2 to 6, b) from 0.1 to 25% by weight, preferably from 1 to 5% by weight, based on the total quantity of component A), of polyhydrazocarbonamide particles or polyurea and polyhydrazocarbonamide particles, c) from 50 to 90% by weight, based on the total quantity of the isocyanate-reactive constituents of component A), of isocyanate-reactive polyether polyols and optionally polyester polyols with equivalent weights from 500 to 5000 g/mol, preferably from 900 to 2200 g/mol, and functionalities from 2 to 6, d) catalysts, e) blowing agents, f) optionally auxiliaries and additives B) an isocyanate component with from 20 to 33% by weight content of isocyanate groups, preferably from 25 to 33% by weight,