New evaluation of interfacial and mechanical properties of thermally-treated Pine/CFRP composites using electrical resistance measurement

Interfacial and mechanical properties of two thermally-treated (at 160 and 200 degrees C) pine/carbon fiber reinforced plastic (CFRP) composites were evaluated using mechanical wettability and electrical resistance (ER) methods. The wetting affinity between pine and epoxy adhesive and the associated spreading of epoxy resin on pine a surface was measured by placing drops of epoxy directly on the surface. Izod, 3-point bending and lap shear tests combined with ER measurements were used to determine the mechanical and interfacial properties of pine and pine/CFRP composites. The interfacial properties pine treated at 160 degrees C, exhibited the highest mechanical properties than those of the untreated and 200 degrees C treated pines. Changes in ER for the 160 degrees C treated pine for the Izod and 3-point bending tests results was small, but significant changes in ER were observed for both neat pine and pine treated at 200 degrees C for these tests. This is likely due to mechanical deterioration as a result of thermal degradation for 200 degrees C treated pine. This improvement in interfacial and mechanical properties at 200 degrees C is attributed to the hardening and reinforcement effects at the interface possibly due to the reduction in moisture in the pine. If the impact shock was applied to the pine parts in pine/CFRP composites, the monitored ER was dependent upon the thermal treated pine conditions. There was the some correlation among thermal treated pines, ER, and their fracture patterns.