Investigation on the Influence of Temperature, Pressure and Curing Time on the Mechanical Properties of Metal Skins and CFRP Core Sandwich Panels Manufactured by Means of Curing-by-Forming Process

In the research presented in this paper, the influence of the manufacturing process conditions on the elastic-plastic mechanical behavior of laminate structures made of metal skin (MS) and carbon fiber reinforced polymer (CFRP) core is investigated by means of laboratory experiments. The specimens are realized with 0.4 mm thick AISI-304 sheets, +/- 45 degrees high modulus carbon fibers woven for the core (8 x 0.25 mm layers stacked) with a thin interlayer made of Loctite EA9460 epoxy adhesive utilized to increase to joining strength between steel skins and CFRP core. The MS-CFRP plates have been manufactured by means of curing-by-forming process considering the following levels for the DoE analysis: i) mold temperature: 130 degrees C, 150 degrees C and 170 degrees C; curing pressure: 4000 kgf, 6000 kgf, and 8000 kgf; and curing time: 10 min., 15min. and 20min., respectively. The manufactured plates have been cut by waterjet process and tested by means of 3-point bending tests, allowing to correlate the above-mentioned process parameters to the mechanical properties of the material. The results have been summarized in processing maps those allow predicting the mechanical properties of the material according to the process parameters utilized in the curing-by-forming process. Finally, based on previous research results, the improvement of the specific mechanical properties of the MS-CFRP structures, in comparison to monolithic AISI-304 steel, have been calculated showing an improvement ranging between 115.5% and 122.4%, for the flexural stiffness and in 306.0% and 569.7% for the failure stress, respectively, depending on the process parameters.