Toughness of Scots pine ‐ polymethyl methacrylate composite

Abstract

A series of 1,600 samples of the sapwood of Scots pine (Pinus sylvestris), part of them in natural state, but majority subjected to polymerization with various level of impregnation with methyl methacrylate, were tested for toughness on Charpy's impact machine. The goal of the experiment was to investigate how polymerization improves toughness and, additionally, how exposure to low temperatures and to the action of seawater influences this property of the material tested. It was found that within impregnation levels and temperatures tested variability of toughness due to these two factors is almost linear and in practical considerations may be predicted based on an empirical formula. It was also found that exposure to the action of seawater weakens the material. To verify anisotropy of toughness in the plane perpendicular to the grain all samples were consistently cut out such that one pair of opposite lateral faces were tangent to the growth rings. Half of the whole set of samples was fractured with an impact directed perpendicular to the growth rings and the other half with an impact directed in the tangential direction. The results show that although in general toughness is slightly higher in the direction perpendicular to the growth rings than in the tangent direction, the difference may be neglected in practical considerations. POLYM. COMPOS., 40:811–822, 2019. © 2018 Society of Plastics Engineers