The Effect of Long-Term Storage on the Compressive Strength Along the Grain of Pine Timber

Abstract

Long-term storage of apolymer, including natural polymer, could significantly affects all its mechanical characteristics. For the accuracy of the experiment, specimens of the same size, breed and humidity were used. The ultimate strength of pine wood was determined in laboratory conditions in 1981 and in 2019 years. The specimens in tests conducted 38 years ago had compressive strength varying from 39.32 to 53.75 MPa, the accuracy rate was 2.77%, which ensures sufficient reliability of the experiment data. In 2019, the average compressive strength of the specimens was from 47.04 MPa to 64.67, and the accuracy rate was 2.68%. The average value of compressive strength along the grain of the core part of wood according to the tests of 1981 was equal to M = 48.83 MPa. The average value of compressive strength along the grain of the heartwood after long-term storage was, according to the tests of 2019, M = 52.89 MPa. The difference between the average values of 48.83 MPa < 52.89 MPa was noted. The value of the compressive strength along the grain of sapwood after long-term storage was slightly higher: by 52.89–48.83 = 4.06 MPa or 7.9%. The reliability of the obtained data was checked by means of the Student’s criterion.