FULL CHARACTERIZATION OF CALYCOPHYLLUM MULTIFLORUM WOOD SPECIE

ABSTRACT:

Wood is a material that for years has been used by man for a variety of purposes, particularly in rural and civil constructions and furniture industry. The possibility of shortages of some wood species, the characterization of other unfamiliar species is an alternative source for use in civil and rural construction. This study aimed to determine, with the aid of Brazilian standard NBR 7190, physical and mechanical properties of Castelo (Calycophyllum multiflorum) wood specie. Twelve determinations were obtained by property, totaling 204 experimental values. In the characterization of wood, regression models were used to estimate the values of timber strength and stiffness as a function of apparent density, being density the physical property more simple to be obtained. The results of mechanical properties showed consistent with the performance of other species used in construction, which highlights the potential use of the Castelo wood in structural design. Regression models, apparent density was considered significant in the estimation of only 4 among the 14 properties for wood strength and stiffness.

KEYWORDS:
Calycophyllum multiflorum; physical-mechanical properties; hardwood; regression model

INTRODUCTION

The use of wood in construction is a practice that has been carried out for many years by mankind, from the need to store food, to overcome obstacles to the construction of shelters (Molina et al., 2013, Almeida et al., 2015). The use of wood for a wide range of purposes depends on the knowledge of its properties (physical, chemical, mechanical and anatomical) for a more rational use of this material, which comes from natural sources, perfectly meets the requirements imposed by the current environmental appeal of products and services provided by man (Almeida et al., 2014).

Due to the demand and the few options of known wood species, selective harvesting has become predatory, reducing market receptivity to new species whose characteristics and properties are not yet fully understood (Souza, 1997).

Due to the great demand associated with few options, the prices of commonly used species increased, providing a new moment for the Brazilian timber sector, requiring the exploration of new wood species with the potential to replace those traditionally used in rural and civil construction (Christoforo et al., 2013). In addition, with increasing population awareness of the use of materials that cause the least damage to the environment, wood from planted forests is a resource of great potential (Almeida et al., 2013).

As an alternative to the diversification of wood use, Calycophyllum multiflorum, a Rubiácea species known as “palo-branco” in Argentina and “Castelo” in Brazil, presents a great option mainly for the state of Mato Grosso, where its production is more pronounced (Baldin & Marchiori, 2015). However, the physical and mechanical properties of this species have not yet been explored and disseminated.

The design of a wood structure, as well as other materials, requires the knowledge of the physical and mechanical properties of the species to be used in the project, allowing the best use of the material (Almeida et al., 2013).

The characterization of wood species occurs by determining their physical properties, strength and stiffness through standardized tests. In Brazil, ABNT NBR 7190 (1997) is the document that defines the parameters for the wood characterization as well as the assumptions and methods used for structural design. However, the drawback of many of these tests is the need to use large equipment and high cost, available in research centers.

A physical property of easy experimental determination consists of the apparent density, defined by the ratio between the mass and the volume of the sample at 12% moisture. Since the density is a basic physical property, its values allows determining an adequate estimate of some wood properties (Almeida et al., 2014; Silveira et al., 2013). The estimation of strength and stiffness properties by density via mathematical models (regression models) allows the engineer, known the density of the wood species chosen and determined experimentally, to estimate the values of strength and stiffness to be used in the pre-designing of the structure.

In order to contribute to the use of new wood species in rural and civil construction, as well as in other applications, this research aimed to characterize Calycophyllum multiflorum wood and evaluate the possibility of estimating strength and stiffness properties due to the knowledge of the apparent density.

MATERIAL AND METHODS

The Calycophyllum multiflorum wood (Figure 1) was properly stored and tested at the Wood and Timber Structures Laboratory (LaMEM) at the School of Engineering of São Carlos (EESC), University of São Paulo (USP), presenting moisture content around 12%.

FIGURE 1
Calycophyllum multiflorum wood specie.

The physical and mechanical properties, obtained in accordance with the provisions of Brazilian Standard ABNT NBR 7190 (1997) – Design of Timber Structures, provided in Annex B “Determination of wood properties for structural designs”, and the number of experimental determinations are presented in Table 1. In total, 3 physical and 14 mechanical properties were obtained, and 204 experimental results were determined.

TABLE 1
Physical and mechanical properties of Calycophyllum multiflorum wood specie.

Properties	Symbol	ND
Apparent density	ρ12	12
Total radial shrinkage	RRT	12
Total tangential shrinkage	RTT	12
Strength in compression parallel to grain	fc0	12
Strength in tension parallel to grain	ft0	12
Strength in tension perpendicular to grain	ft90	12
Strength in shear parallel to grain	fv0	12
Cleavage strength	fs0	12
Flexural strength	fm	12
Modulus of elasticity in compression parallel to grain	Ec0	12
Modulus of elasticity in tensile parallel to grain	Et0	12
Modulus of elasticity in static bending test	Em	12
Parallel hardness	fH0	12
Perpendicular hardness	fH90	12
Toughness	W	12
Strength in compression perpendicular to grain	fc90	12
Modulus of elasticity in compression perpendicular to grain	Ec90	12

• ND – number of determinations.

The estimation of strength and stiffness properties as a function of apparent density was evaluated with the use of regression models (Equations 1 to 4) based on analysis of variance (ANOVA). In equations 1 to 4, Y denotes the dependent variable (wood strength or stiffness), X consists of the independent variable (apparent density) and a and b are the parameters of the models fitted by Least Squares Methods.

(1) $$\begin{array}{cc}Y=a+b\cdot X& [\text{Lin}-\text{Linear}]\end{array}$$

(2) $$\begin{array}{cc}Y=a\cdot e^{b\cdot X}& [\text{Exp}-\text{Exponential}]\end{array}$$

(3) $$\begin{array}{cc}Y=a+b\cdot Ln(X)& [\text{Log}-\text{Logarithmic}]\end{array}$$

(4) $$\begin{array}{cc}Y=a\cdot X^b& [\text{Geo}-\text{Geometric}]\end{array}$$

By the ANOVA of the regression models, considered at the 5% level of significance (α), the null hypothesis formulated consisted in the non-representativeness of the tested models (H₀), and in the representativeness as an alternative hypothesis (H₁). P-value higher than the level of significance considered implies accepting H₀ (the model tested is not representative - variations of ρ₁₂ are unable to explain the variances of the estimated property), refuting it otherwise (the model tested is representative). In addition to the use of ANOVA, which allows or not to accept the representativeness of the models tested, the coefficient of determination (R²) values were obtained as a way of evaluating the capacity of variations in apparent density to explain the analyzed variable, making it possible to choose among the models considered to be significant, the best fit. It should be noted that the apparent density was used to estimate the 14 properties of strength and stiffness with the use of the 4 mathematical models listed in Eq. 1 to 4, totaling 56 adjustments.

RESULTS AND DISCUSSION

Tables 2 and 3 present the mean values ($\overline{x}$), coefficients of variation (CV) and the lowest (Min) and highest values (Max) for physical and mechanical properties, respectively.

TABLE 2
Results of physical properties.

Statistics	ρ12 (kg/m3)	RRT (%)	RTT (%)
$\overline{x}$	770	4.02	6.64
CV(%)	7	14	10
Min	690	3.17	5.72
Max	880	4.87	7.74

TABLE 3
Results of mechanical properties.

Stat.	fc0 (MPa)	ft0 (MPa)	ft90 (MPa)	fv0 (MPa)	fs0 (MPa)	fm (MPa)	Ec0 (MPa)	Et0 (MPa)
$\overline{x}$	55	104	7.00	21	1.4	103	11188	12920
CV(%)	5	15	19	18	21	6	11	15
Min	50	88	3.91	10	1.0	89	9249	10524
Max	59	125	9.73	25	2.10	112	13128	16395

Stat.	Em (MPa)	fH0 (MPa)	fH90 (MPa)	W (N·m)	fc90 (MPa)	Ec90 (MPa)
$\overline{x}$	11457	101	65	14.24	12	647
CV(%)	12	8	5	15	18	17
Min	9886	91	59	11.88	9	502
Max	14471	106	71	18.53	17	825

Based on the sample values (12 samples) of the strength in compression parallel to grain, the characteristic value (f_c0,k) found according to the Brazilian standard ABNT NBR 7190 (1997) was equal to 55 MPa, which classifies the Calycophyllum multiflorum wood belongs to the D40 strength class. The value obtained from f_c0 (55 MPa) for Calycophyllum multiflorum wood is very close to that obtained for Amescla-Aroeira (59.03 MPa) from the research developed by Logsdon et al. (2005), being Amescla-Aroeira a wood used in structures but that is in extinction, evidencing the possibility of the use of Calycophyllum multiflorum wood in structures of medium to large dimensions.

The strength in compression parallel to grain (55 MPa) of the Calycophyllum multiflorum wood is much higher than the compressive strength values of Paricá wood [24 MPa] (Almeida et al., 2014), Toona ciliata [27 MPa] (Braz et al. 2013) and Eucalyptus benthamii Maiden et Cambage [37.34 MPa] (Müller et al., 2014), both wood with potential for use in construction.

The mean value obtained from the apparent density [0.770 g/cm³] of Calycophyllum multiflorum classifies it as a heavy wood (Melo et al., 1992), being the same classification as Minquartia guianensis, Lecythis poiteaui, Mezilaurus itauba, Manilkara huberi and Brosimum rubescens (Silveira et al., 2013), however, is still lighter than the species mentioned above, whose densities range from 0.835 to 0.904 g/cm³. It is denser than medium apparent density woods, such as Liquidambar sp. (Freitas et al., 2015), Pinus and Teca (Almeida et al., 2014), Cedrela fissilis, Clonal hybrids and Hovenia dulcis (Motta et al., 2014), ranging from 0.478 to 0.577 g/cm³. Light wood, such as Toona ciliata (Braz et al., 2013), Paricá (Almeida et al., 2013) and Gallesia integrifólia (Motta et al., 2014) have a density varying between 0.318 g/cm³ and 0.370 g/cm³.

The Brazilian standard ABNT NBR 7190 (1997) stipulates maximum values for the coefficient of variation for the characterization to be qualified as adequate, being 18% for strength to normal stresses and 28% for tangential stresses, it should be noted that practically all properties have met the requirements of this normative document.

Table 4 shows the best fits (based on the coefficient of determination) obtained from the ANOVA of the regression models for the apparent density as an estimator of the strength and stiffness values, with the significant property adjustments by ANOVA being underlined (P-value < 0.05).

TABLE 4
Regression models for estimating the strength and stiffness values of Calycophyllum multiflorum wood by apparent density.

Properties	Model	P-value	a	b	R2
fc0	Geo	0.0078	62.4685	28.6092	52.09%
ft0	Lin	0.0971	-2.6904	138.4647	25.09%
ft90	Lin	0.9743	6.7152	0.3602	0.01%
fv0	Lin	0.2526	0.8667	26.6667	12.84%
fs0	Lin	0.4257	2.6159	-1.6169	6.45%
fm	Log	0.7132	105.9627	11.1012	1.41%
fH0	Exp	0.3094	69.7883	0.4756	10.28%
fH90	Lin	0.1807	46.0674	25.2107	17.15%
W	Lin	0.0745	-1.2947	20.2352	28.37%
fc90	Log	0.0000	21.3653	33.5308	85.23%
Ec0	Log	0.0088	14519.9203	12483.8686	51.25%
Et0	Lin	0.0040	-7489.3149	26591.7241	58.06%
Em	Exp	0.0002	2911.5235	1.7773	75.48%
Ec90	Lin	0.0030	-569.2238	1578.4674	60.19%

The density was considered significant only in the estimation of the strength in compression parallel to grain (f_c0) [R² = 52.59%] and in the strength in compression perpendicular to grain (f_c90) [R² = 85.23%]. By the values of the determination coefficients obtained from these two models, it is verified that apparent density only provides good precision as an estimator of the f_c90. The best fit for the estimation of f_c0 and f_c90 by ρ₁₂ were the geometric and logarithmic, respectively, illustrated in Figure 2.

FIGURE 2
Best fit obtained to estimate the strength values of wood by apparent density - geometric (a) and logarithmic (b) models.

The apparent density was considered significant by ANOVA in the estimation of all stiffness properties evaluated (P-value <0.05). The best fit was obtained for the modulus of elasticity in the static bending using the exponential model [R² = 75.48%] (Figure 3c), followed by the modulus of elasticity in compression perpendicular to grain [R² = 60.19%] (Figure 3d) with the linear model, by the modulus of elasticity in tensile parallel to grain [R² = 58.06%] (Figure 3b) with the use of the linear fit and finally by the modulus of elasticity in compression parallel to grain [R² = 51.25%] (Figure 3a) with the use of the logarithmic fit.

FIGURE 3
Best fit obtained to estimate the stiffness values of wood by apparent density.

From the adjustments considered significant in Table 4, only the strength in compression perpendicular to grain and the flexural modulus of elasticity are effectively considered as good adjustments, since they have coefficients of determination higher than 70%. It should be noted that Almeida et al. (2014) found good regression models (R²> 70%) in the estimation of hardness of the hardwoods group as a function of apparent density, and these results were justified by the use of species of different densities.

CONCLUSIONS

The results obtained from the present research allow concluding that:

• –

  From the values of the variation coefficient obtained, the characterization of Calycophyllum multiflorum wood specie can be considered as required by the Brazilian standard;

• –

  Following the parameters of the Brazilian standard, this wood is classified as belonging to D40 strength classes, because it presents a characteristic value of compressive strength equal to 55.00 MPa, indicating its potentiality of use in rural construction, among other applications, when comparing the results of their mechanical properties with those from other hardwoods already reported;

• –

  By the values of the coefficient of determination obtained from the adjustments, the apparent density showed to be a good estimator only for the strength in compression perpendicular to grain and for the modulus of elasticity in static bending test, evidencing that it is possible to estimate these two properties with the knowledge of the density of Calycophyllum multiflorum wood (experimentally measured) to be used in the design, allowing a more precise pre-dimensioning of the structure.

ACKNOWLEDGMENTS

We would like to thank the Coordination for the Improvement of Higher Education Personnel (CAPES) and the National Council for Scientific and Technological Development (CNPq) for all the support provided in the development of this research.

REFERENCES

• ABNT - Associação Brasileira de Normas Técnicas (1997) NBR 7190. Projeto de estruturas de madeira. Rio de Janeiro, ABNT, 107p.
• Almeida DH, Chahud E, Almeida TH, Christoforo AL, Branco LAMN, Lahr FAR (2015) Determination of Density, Shear and Compression Parallel to the Grain Strengths of Pariri (Pouteria sp.), Brazilian Native Wood Specie. International Journal of Materials Engineering 5(5):109-112.
• Almeida DH, Scaliante RM, Christoforo AL, Varanda LD, Lahr FAR, Dias AA, Junior CC (2014) Tenacidade da madeira como função da densidade aparente. Revista Árvore 38(1):203-207.
• Almeida DH, Scaliante RM, Macedo LB, Macêdo NA, Dias AA, Christoforo AL, Junior CA (2013) Caracterização completa da madeira da espécie amazônica Paricá (Schizolobium amazonicum HERB) em peças de dimensões estruturais. Revista Árvore 37(6):1175-1181.
• Baldin T, Marchiori JNC (2015) Descrição anatômica de Calycophyllum multiflorum griseb. (Rubiaceae), Balduina (49):16-23, 30-VIII.
• Braz RL, Oliveira JTS, Rodrigues BP, Arantes MDC (2013) Propriedades físicas e mecânicas da madeira de Toona ciliata em diferentes idades. Floresta 43(4):663-670.
• Christoforo AL, Blecha KA, Carvalho ALC, Rezende LFS, Lahr FAR (2013) Characterization of Tropical Woods Species for Use in Civil Constructions. Journal of Civil Engineering Research 3(3):98-103.
• Freitas TP, Feuchard LD, Oliveira JTS, Paes JB, Arantes MDC (2015) Caracterizações anatômicas e físico-mecânica da madeira de Liquidambar sp. Floresta 45(4):723-734.
• Logsdon NB, Finger Z, Estevão JG (2005) Descrição Dendrológica e caracterização físico-mecânica da madeira de Amescla-aroeira, Protium heptaphyllum (Aubl) March. (Burseraceae), Revista Madeira: Arquitetura e Engenharia, 6(17):13.
• Melo JE, Coradin VTR, Mendes JC (1992) Classes de densidade para madeiras da Amazônia brasileira. Silvicultura. Anais. Congresso Florestal Brasileiro 12(42):695-699.
• Molina JC, Calil Neto C, Christoforo AL, Segundinho PGA (2013) Avaliação da estabilidade de pontaletes de madeira a partir da aplicação de carregamentos centrados. Revista Madeira: Arquitetura e Engenharia 14:23-36.
• Motta JP, Oliveira JTS, Braz RL, Duarte APC, Alves RC (2014) Caracterização da madeira de quatro espécies florestais. Ciência Rural 44(12):2186-2192.
• Müller BV, Rocha MP, Cunha AB, Klitzke RJ, Nicoletti MF (2014) Avaliação das Principais Propriedades Físicas e Mecânicas da Madeira de Eucalyptus benthamii Maiden et Cambage. Floresta e Ambiente 21(4):535-542.
• Silveira LHC, Rezende AV, Vale AT (2013) Teor de umidade e densidade básica da madeira de nove espécies comerciais amazônicas. Acta Amazônica 43(2):179-184.
• Souza MH (1997) Incentivo ao uso de novas madeiras para a fabricação de móveis. Brasília, IBAMA. 70p.

Publication Dates

• Publication in this collection
  Jul-Aug 2017

History

• Received
  16 Aug 2016
• Accepted
  15 Mar 2017