Transverse Compression Behavior of Softwood and Alternately Laminated Lumber of Rubberwood Veneer and Falcata Veneer

Abstract

Softwood and alternately laminated lumber of rubber wood veneer and falcate veneer were compressed transversely. On the assumption that softwood and alternately laminated lumber are recognized as laminated composite structure of soft layer and hard layer, transverse compression strength of them are expected to be larger than that of lumber only of weaker layer (earlywood and falcate veneer). Cross section of transversely compressed softwood was observed using digital image correlation for strain analysis, and large shear strain has progressed on earlywood at edge of the softwood specimen. The cross section of the specimen after compression was examined under an incident-light microscope, so it was found that compression crush lines began on the boundary between earlywood and latewood at the edge of the specimen. It is probably because of shear stress generated at the boundary between soft layer and hard layer, that is, latewood of high-density would prevent earlywood of low-density from deforming under compression stress. However, when alternately laminated lumbers which are a similar structure to softwood were compressed transversely, shear strain was found not at the edge but at the inner part of the specimen. Moreover compression strength of alternately laminated lumber has been no larger than laminate lumber of falcate veneer. The area of large shear strain has formed inclined lines on the laminated lumber under compression stress, and the lines tended to coincident with checks formed by rotary peeling using a lathe. The lathe checks would mitigate the restriction of hard layer (rubber wood veneer), and so the alternately laminated lumber may not behave similar to softwood.