Study On The Mechanical Properties Of Epoxy Foam And Sandwich Structure

Because of the characteristics of lightweight, high-strength, composite sandwich structures are widely used in the field of aerospace, transportation, construction, shipbuilding et al. But composite sandwich structure also has its disadvantages, such as low strength, very sensitive to the impact load, so researching sandwich composite structure flexural properties and impact damage have very great significance.A kind of epoxy resin foam was prepared. The influence of temperature on epoxy foam quality is investigated. As the foaming temperature increasing, the numbers of nuclear will be decreased, the cell density will be decreased, the average size of the cell will be increased, and the foam density will be decreased. But when the temperature is too high, the number of bubbles is too small, the resin matrix is less foaming, and could be burnt. The foam compressive strength, compressive modulus, tensile strength, tensile modulus could be regard as the function of foam density. Within this study, Based on experimental data, Relationship between compressive strength, compressive modulus, tensile strength, tensile modulus and density is fitted: X:= 1.55 ! 10;<! !=.>?,E@= 5.80 ! 10AB! !C.DE,-XF= 1.49 ! 10GH!!I.JK,-EL= 3.76 ! 10MN! !O.PQ experimental data and fitting results have good correlation.Type-hat/type-bubble/type-I, three kinds of composite sandwich structure panel are fabricated, and three-point bending test are carried. The results showed that: type-hat sandwich structure panel having the highest bending stiffness and strength. A variety of failure modes can be seen on three kinds of sandwich structure panel. Three kinds of failure modes/up face sheet crush/core shear failure, the face plate warping,could be seen. For the type-bubble and type-I sandwich structure, panel warping could be seen. Three sandwich panel bending strength between experimental value and finite element values are very close.Stiffener was added to study the influence on bending stiffness and bending strength of sandwich panel filled with epoxy foam. The results showed that: the stiffener can significantly improved bending stiffness and bending strength of sandwich structure panel with foam core in the case of a small increasing in quality.With increasing of impact energy, pit depth and pit diameter gradually increases, and damage area seen from the C-scan image also increases. Under all impact energy,impact damage was not found on the down plate, which is different from laminate p late. The foam core in sandwich structures effectively could absorb the impact energy,avoiding the impact energy transfer to the down plateImpact energy can influence the damage modes for sandwich structures. Under lower impact energy, resin crush and delaminating are main damage mode; under upper impact energy, fiber crack is the main damage mode.