On the variability of transverse elastic properties of P. pinaster at the cellular level

Transcription

1 COST Action FP0802 Thematic workshop: Mixed numerical and experimental methods applied to the mechanical characterization of bio based materials On the variability of transverse elastic properties of P. pinaster at the cellular level João Pereira, José Xavier, Pedro Couto, José Morais, José Lousada, Pedro Melo Pinto April 27 28, 2011 Vila Real, Portugal

2 OUTLINE INTRODUCTION ANNUAL RING LEVEL - X-Ray microdensitometry - Cellular geometrical characterisation CONCLUSIONS & OUTLOOK 2

3 INTRODUCTION Wood material why wood? - Important forest resources on Earth - Renewable/Recyclable - Important engineering material - Has good stiffness/weight ratio why Pinus pinaster? - Important Portuguese natural resource - Traditional structural material - Important raw-material for carpentry and furniture why RT plane? - Lack of mechanical characterisation - Need better understanding of structural/mechanical relationships 3

4 INTRODUCTION Scale of observation: Annual ring level - Earlywood(EW)/latewood(LW) heterogeneity - Cellular geometrical characterisation 4

5 ANNUAL RING LEVEL: X-Ray microdensitometry Material and methods Wood samples: 120(R)x5(L)x5(T) (mm) Microdensitometer (spatial resolution = 0.1 mm) X-Ray chamber X-Ray film (X-Ray film: optical density) 5

6 ANNUAL RING LEVEL: X-Ray microdensitometry Density profile Density (g.cm-3) Width (mm) % Ring average earlywood latewood ring earlywood latewood Latewood Heterogeneity index AR AR

7 Cellular model Regular hexagon model (adapted from Thuvander et al, 2000) Structure/elastic properties relationships: 7

8 Proposed work How the geometrical parameters of the cell model (t, h, d1, d2, l, q) vary within individual annual ring and radially along the stem of the tree? Consequently, how the transverse elastic properties of P. pinaster vary within individual annual ring and radially along the stem of the tree? 8

9 Material and methods Sample preparation (wood slices) Wood specimens: 15(R)x10(L)x8(T) (mm) Autoclave Sliding knife microtome Entellan 9

10 Material and methods Image acquisition Optical fluorescence microscopy (Olympus BX 50 at 200x magnification) AVT Dolphin F-201C digital camera (1280x960 pixel; conv. factor = 0.46 mm/pixel) 10

11 Material and methods Image processing tools Gimp ; Matlab Adjacent images overlapping: Annual ring reconstruction 11

12 Drawing CAD tools: AutoCAD R10 Earlywood drawing maps Cellular structure mesh Net maps (cell geometry) Boundary maps (lumen geometry) 12

13 Drawing CAD tools Earlywood measurements 13

14 Drawing CAD tools Latewood drawing maps Cellular structure mesh Net maps (cell geometry) Boundary maps (lumen geometry) 14

15 Drawing CAD tools Latewood measurements 15

16 Results AR10 AR41 16

17 Results AR10 AR41 17

18 Results AR10 AR41 18

19 Results AR10 AR41 19

20 Results AR10 AR41 20

21 Results AR10 AR41 21

22 Estimation of elastic properties: Earlywood 18.92% 48.61% 67.22% 16.86% 22

23 CONCLUSIONS & OUTLOOK CONCLUSIONS - Cellular geometrical parameters were identified for P. pinaster wood within annual ring and along the stem, using CAD tools; - The radial variation of transverse elastic properties was estimated from the cellular geometrical parameters based on hexagonal unit cell model. The trend of variation indicates an increase of elastic properties from the innermost to the outermost of the stem. 23

24 CONCLUSIONS & OUTLOOK Simple segmentation Edge detection Multiple edge detection Multiple segmentation OUTLOOK - Enhance automatic image processing and analyses for geometrical parameters characterisation; Boundary maps (lumen geometry) 24

25 CONCLUSIONS & OUTLOOK OUTLOOK - Assessing the radial variation of transverse elastic properties by mechanical testing at the annual ring scale. 25

26 CONCLUSIONS & OUTLOOK Thank you João L. Pereira Wood Engineering Dpt. at Viseu High School of Technology (PhD Student at UTAD) Special thanks to Professors: José Xavier; José Morais; José Lousada 26