Mechanical modeling of bending stiffness degradation for soft-honeycomb sandwich structure under CW laser heating

Based on the theory of Reissner’s sandwich structure bending, a mechanical model of bending stiffness degradation for a soft-honeycomb sandwich structure under continuous wave (CW) laser heating was established by introducing the equivalent debonding coefficient of adhesive and elastic modulus temperature dependence of panels. To verify the rationality of the mechanical model, a real-time bending stiffness measurement system for a soft-honeycomb sandwich structure under CW laser heating was proposed using the overhanging beam three-point bending method. The results show that the mechanical model works good to describe the decreasing trend of the soft-honeycomb sandwich structure under CW laser heating and to predict the residual bending stiffness after CW laser heating, despite the fact that in the early stage of CW laser heating, the bending stiffness of some kind of soft-honeycomb sandwich structure may increase for a short time due to the pyrolysis gas production. However, with the overflowing of pyrolysis gas and the elastic modulus of panel degradation at a high temperature, the bending stiffness of soft-honeycomb sandwich structure declines rapidly and soon fails to withstand any bending load. The research shows that special attention should be paid to the effect of laser heating on the mechanical properties of the soft-honeycomb sandwich structure. It also enlightens the study of mechanical properties and temperature dependence of the honeycomb sandwich structure at a high heating rate.