Charpy Impact of Sandwich Structural Composites (CFRP/PC/CFRP) of Polycarbonate (PC) Cores Covered with Carbon Fiber Cross Textile Reinforced Epoxy Polymer (CFRP) Thin Sheets as a Function of Temperature

The purpose of this study is to investigate a lighter, cheaper and possibly stronger alternative to CFRP, by obtaining the Charpy impact values (a(uc)) of a sandwich structural composite (CFRP/PC/CFRP) constructed of a polycarbonate (PC) core between two thin plies of carbon cross textile fiber/epoxy (CFRP) within the temperature range of aircraft operation, from 200 to 403 K below the glass transition temperature of PC (T-g = 422 K). The a(uc) of CFRP/PC/CFRP were compared with a 2.0 mm thick 12-ply CFRP laminate. Results showed overall, the CFRP/PC/CFRP had higher a(uc) than the CFRP at each fracture probability (P-f) from 300 to 373 K except at 200 K with low Pf and 403 K with high Pf. Specifically, although the volume fraction of carbon fiber (12%) of CFRP/PC/CFRP was much smaller than that (60%) of the CFRP, the a(uc) at room temperature (300 K) of CFRP/PC/CFRP was approximately 64% higher than that of CFRP at mid-fracture probability (P-f) of 0.50. Fracture modes of CFRP/PC/CFRP were explained by delamination between PC core and the CFRP thin sheet surfaces, bending plastic deformation, and CFRP fracture. The highest Weibull coefficient (n) was obtained at 323 K. Based on the 3-parameter Weibull equation, the limiting impact value (a(s)) also exhibited the highest value at 323 K. In addition, the cost of CFRP/PC/CFRP was 40% lower than that of CFRP at the time of this study. Since the use of PC resin as the core enhanced the safety design at low cost, practical use of sandwich structural composites of CFRP/PC/CFRP is possible. [doi:10.2320/matertrans.M2011357]