Evaluation of the failure modes of the fingerjointed timber species for utilization of waste timber.

Abstract

Off-cut wood pieces are often dumped by sawmills as they are considered to be wastes in the wood industry. A certain portion of timber has to be removed also due to inadequate length of sawn timber material. Finger jointing technique is used to eliminate wood defects which weaken the strength of sawn wood plank and unused short pieces can even be used for obtaining defect free longer lengths of timber. A study was undertaken to evaluate the tensile strength performance and major failure modes of the finger-jointed productions. A finger profile of 13 mm finger length, 4 mm pitch and 1 mm tip width were used in the study. The sections were joined using PVAc adhesive. BS 373: 1957 and BS EN 15497:2014 were used as standards for tests. The test for tensile properties were performed using Universal Testing Machine (UTM 100 PC) with loading plate moving speed of 01mm/min. Load vs. displacement variation was obtained and maximum load was identified to calculate ultimate tensile strength for evaluating the major failure modes. Density and major finger joint failure modes were also investigated. The major failure mode of the finger- jointed seven timber species subjected to a tensile test was mainly due to glue line failure (47.14%), followed by wood grain failure (24.28 %) and fiber failure(15.71%). The least failure mode was recorded as weak finger joint (12.85 %). The highest mean finger joint strength was obtained from Grandis (50.23 N/mm2) timber species and least mean finger joint strength was recorded in Kumbuk (16.88 N/mm2) timber species. There is no considerable relationship between Density and the failure occurrence of finger-jointed timber species. This results would be benefited for finger-jointed furniture manufacturing industry for sustainable use of wood waste.