Influence of carbon fibre layers on the strength of thermally modified laminated veneer lumber

Perçin, Osman; Ülker, Onur

doi:10.1590/0104-1428.20220070

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Original Article • Polímeros 33 (1) • 2023 • https://doi.org/10.1590/0104-1428.20220070 copy

Influence of carbon fibre layers on the strength of thermally modified laminated veneer lumber

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Thermally modification of wood is an environment-friendly alternative method for improving several properties of wood without the use of chemicals. The compressive strength (CS) parallel to the grain of reinforced laminated veneer lumber (LVL) manufactured from heat treated beech (Fagus orientalis) veneers and carbon fibre was determined. Thermally modification was performed at 140°C, 160°C, 180°C, and 200 °C according to thermal treatment process. Carbon fibre were added as a reinforcement layer between wood veneers bonded with phenol-formaldehyde (PF), polyvinyl acetate (PVAc) polyurethane adhesives (PU) to improve properties of LVL. Results showed that reinforcing LVL panels with carbon fibre increased both density and CS. The PF adhesive showed better results for reinforced LVL panels with carbon fibre. The anatomical structure and density of the wood material significantly affect its mechanical properties, including compressive strength parallel to the grains. Wood density had a strong significant linear relationship with CS.

Keywords:
laminated veneer lumber; carbon fibre; thermal treatment process; beech

Group of Samples	Heat Treatment (°C)	Density (g mm^-3) (Mean value)	Min (g mm^-3)	Max (g mm^-3)	SD (Standard Deviation)	Changes (%)
Solid Wood beech (Fagus orientalis)	Control	0.691	0.655	0.731	0.025	-
	140	0.684	0.657	0.719	0.017	-1.02
	160	0.672	0.653	0.698	0.016	-2.83
	180	0.663	0.639	0.697	0.015	-4.22
	200	0.648	0.614	0.683	0.020	-6.64
PVAc-LVL	Unheated	0.717	0.685	0.751	0.020	3.63
	140	0.707	0.675	0.733	0.017	2.26
	160	0.693	0.668	0.711	0.015	0.29
	180	0.684	0.645	0.722	0.025	-1.02
	200	0.673	0.631	0.699	0.000	-2.67
PF-LVL	Unheated	0.727	0.708	0.748	0.014	4.95
	140	0.716	0.681	0.755	0.024	3.49
	160	0.706	0.673	0.745	0.021	2.12
	180	0.695	0.676	0.723	0.016	0.58
	200	0.685	0.668	0.707	0.013	-0.88
PU-LVL	Unheated	0.715	0.679	0.724	0.014	3.36
	140	0.711	0.685	0.739	0.019	2.81
	160	0.694	0.663	0.749	0.023	0.43
	180	0.686	0.652	0.721	0.021	-0.73
	200	0.675	0.649	0.695	0.016	-2.37
PVAc-RLVL	Unheated	0.753	0.732	0.775	0.015	8.23
	140	0.744	0.698	0.779	0.025	7.12
	160	0.731	0.676	0.763	0.026	5.47
	180	0.721	0.673	0.759	0.027	4.16
	200	0.713	0.665	0.743	0.028	3.09
PF-RLVL	Unheated	0.776	0.739	0.799	0.019	10.95
	140	0.763	0.747	0.789	0.012	9.44
	160	0.752	0.715	0.779	0.019	8.11
	180	0.742	0.699	0.773	0.025	6.87
	200	0.733	0.681	0.769	0.024	5.73
PU-RLVL	Unheated	0.754	0.705	0.776	0.020	8.36
	140	0.748	0.721	0.766	0.015	7.62
	160	0.729	0.695	0.769	0.024	5.21
	180	0.722	0.685	0.751	0.023	4.29
	200	0.712	0.688	0.745	0.019	2.95

Group of Samples	Heat Treatment (°C)	CS (N/mm²) (Mean value)	SD (Standard deviation)	HG (Homogeneity groups)	Changes (%)
Solid Wood (Beech)	Control	68.62	3.83	P	-
	140	69.11	4.31	OP	0.71
	160	71.27	3.37	M	3.72
	180	67.48	3.02	Q	-1.69
	200	64.21	3.10	S	-6.83
PVAc-LVL	Unheated	69.53	3.58	O	1.31
	140	72.47	3.86	L	5.31
	160	74.61	3.48	K	8.03
	180	72.71	4.11	L	5.63
	200	64.29	3.76	S	-6.80
PF-LVL	Unheated	72.29	4.05	L	5.08
	140	74.62	3.85	K	8.04
	160	77.58	3.22	I	11.55
	180	77.07	3.69	IJ	10.96
	200	72.98	4.04	L	5.97
PU-LVL	Unheated	70.49	4.41	MN	2.65
	140	72.91	3.46	L	5.88
	160	75.37	3.90	K	8.96
	180	69.72	4.09	NO	1.58
	200	65.49	4.31	R	-4.78
PVAc-RLVL	Unheated	76.37	3.56	J	10.15
	140	80.22	4.57	G	14.46
	160	83.11	4.21	E	17.43
	180	78.89	3.98	H	13.02
	200	69.33	4.35	OP	1.02
PF-RLVL	Unheated	82.19	4.29	F	16.51
	140	86.11	3.44	C	20.31
	160	90.61	3.59	A	24.27
	180	88.47	3.47	B	22.44
	200	83.34	3.33	DE	17.66
PU-RLVL	Unheated	76.45	3.41	J	10.24
	140	80.34	3.76	G	14.59
	160	83.96	3.46	D	18.27
	180	76.57	3.14	J	10.38
	200	74.65	3.37	K	8.08

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