[week 21] process reflection

Between the planning made in the learning plan and reality are some differences:

week	planning		reality

February 2008	zoeken opdracht en verzamelen theorie		discussing materializing the pavilion as assignment
March 2008	kritische analyse opdracht en theorie		Analyzing case
June 2008	P1: voorlopig leerplan		P1:learning plan
Oktober 2008	vaststellen methode+eis		Determination criteria
	ontwerpen en afwegen variant		Designing options
1-7 november 2008	vaststellen te onderzoeken bouwdeel		Determination building part
10-14 november 2008	terugkoppeling onderzoek naar ontwerp		Applying research in design
17-21 november 2008	ontwerp aanpassen aan knelpunten		Design adjustments to problems
24-28 november 2008	praktische uitwerking klimaat, veiligheid, pve		Integrating functional criteria
1-5 december 2008	detailleren te onderzoeken bouwdeel		Detailing building part
8-12 december 2008	berekenen te onderzoeken bouwdeel		Calculating building part
15-19 december 2008	voorbereiden voor experimentele proef			Visualising
5-9 januari 2009	P2: leerplan en voorlopig ontwerp/onderzoek			P2: shape options and conclusion
12-16 januari 2009	voorbereiden voor experimentele proef			Analyzing problem
19-23 januari 2009	bouwen experimentele proef			Three connection problems
26-30 januari 2009		uitvoeren experimentele proef		Overview design options
2-7 februari 2009		verwerken experimentele proef		Preparation mechanical testing
9-14 februari 2009		P3: plan voor generieke kennis en toepassing		Building rib variants
16-21 februari 2009	report plan for research		testing
23-28 februari 2009	making priliminary mock ups for discussion		Functional unit, Processing test results
2-7 maart 2009	presentatie P4: definitief ontwerp/onderzoek		Options with ribs
9-14 maart 2009	verwerken commentaar P4		Design of entire building
16-21 maart 2009	afmaken prototype/maquette		LCA comparison
23-28 maart 2009	voorbereiden presentatie		P3: plan for options
30 maart - 3 april '09	presentatie P5: conclusies, project en proces		methodology
6-11 april 2009			Generative tool
13-19 april 2009			materials
20-25 april 2009			material selection
27 april-1 May 2009			System design
4-9 May 2009			Report, Multi criteria
11-15 May 2009			Reflection and conclusions
18-22 May 2009			making priliminary mock ups
25-30 May 2009			presentatie P4: final research
1-6 June 2009			Strength and durability of Kenaf
8-12 June 2009			detail design
15-18 June 2009			Report, Multi criteria
22 -27 June 2009			Reflection and conclusions
29 June 2009			P5: making mock up

As can be seen in the table above, some steps have started later or took longer than foreseen. This is mainly because the design process is not linear but a cycle. There have been made several options that have been tested and processed.

The colors indicate the same kind of task. Most colors occur in both planning and reality. The bright red fields indicate decision moments that have not been planned.

[week 20] multi criteria comparison

The same functional unit requirements makes it possible to compare the system designs. System design 4 is not complying to the requirement of a thin rod package because of the bracings.

There is some uncertainty in use time, dimensions and environmental index. Especially the kenaf core construction still has some uncertainties and topics for further research.

The C2C bonus is the added value of the material next to the functional unit. Biosphere materials have the possibility of energy recovering after use.

The table below compares known variables for an end grade. Higher numbers are better. Numbers are therefore normalized with best practice =1.

name	function	Environmental index	C2C bonus	total +factor
1. technical	o	0,19 +- 10%	O	0,19
2. steel- wood	o	0,13 +- 10%	O	0,13
3. kenaf core tube	o	0,56 +- 10%	+	0,84
4. wood joints	-	1,0 +- 10%	+	1
5. solid wood	o	0,1 +- 10%	+	0,15

Because of not fitting the functional unit the wood joints are not chosen as final design.

Kenaf core tubes are the best option in total.

[week 17] presentation

Everyone interested is invited to my presentation:

[week 19] Strength and durability of Kenaf Stressed Skin Panel extrusion

design

Agricultural fibres can be pressed or extruded to plate material. The design that is elaborated here exists of kenaf particles extruded to a tube.

Kenaf (Hibiscus cannabinus) is a fast growing fiber crop related to cotton, okra, and hibiscus. The plants, which reach heights of 2,4 to 6 meters, are harvested for their stalks from which the fiber is extracted. The fiber is used in the manufacture of industrial textiles, ropes, and twines. Kenaf is among the most widely utilized of the bast fibers. (CES EDUPACk 2009)

Harvesting of Kenaf, source: http://bridgemail.bigbridge.com.au

Panasonic has set up a plant in Malaysia to manufacture kenaf core fibre boards and export them to Japan. Kenaf core fibres are comparable to hard wood. (http://en.wikipedia.org/wiki/Hibiscus_cannabinus)

source: http://www.stramit-int.com/index.html

variables

Input

Fibre type (kenaf core)

holocellulose content (71.24%)

lignin content (23.22%)

ash content (5.93%)

Kenaf core is a product from the flax plant. The properties of resin free fibreboard are superior to wheat straw, reed, palm or meadow (Jianying Xu 2006).

Fibre length (5,5 +- 2,49mm) 1,6//8 cm

Fibre length balances between modulus of elasticity and modulus of rupture.

Fibre diameter (284 +- 136 µm)fiber width (0.82–1.73 mm) cell wall thickness (3.36–5.25 lm) lumen diameter (5.82–10.39 lm)

Resin type (none)

Most fibre boards contain UF or MDI glues. Sometimes the natural lignin in the fibres can provide the necessary bonding.

Resin content (0 %)

Steam-injection during pressure -> yes

Steam injection gives better properties to the board (widyorini2005)

Pressure (0,6 MPa) 0,6/0,8

This results in a density (500 kg/m³). 300

Time of cooking (10min) 20/30

Cooking of fibres before bonding gives higher internal bonding and less thickness swelling.

Test conditions

Relative humidity (10-90%)

Outcomes

Modulus of Elasticity MOE (2,3 ± 0,1 MPa)

Modulus of Rupture MOR (19.4 ± 2,0 MPa)

Internal Bond IB (0,24 ± 0,04 MPa)

Thickness Swelling TS (18 ± 1 %)

design strength performance

height 350 mm

width 1200 mm

flange thickness 28 mm

web thickness 28 mm

Elastic deformation

MOE of 2,3 MPa results in a vertical deformation of the roof of 5/384*1,7*9000^4/ (2400*2*28*1200*175^2)= 29 mm. This is within the tolerance of 45 mm.

Long term deformation

Long term deformation caused by creep is not investigated yet. MDF shows a a comparable creep behaviour that could be studied. Conclusions from this study (Fernandez1998) are that the stress should remain below 20% of MOR to avoid rupture. Also a high relative humidity should be avoided.

Stressed Skin Panel tests with wood webs and OSB flanges showed that tests on deformation and Modulus of Elasticity showed similar outcomes (Kliger 1995).

bending strength

With a MOR of 17,4 MPa and a bending resistance of 2,1 *10^9 mm⁴ is a bending moment of 204 kNm possible. The designed load of 21 kNm is below this.

compression strength

The roof leans on the walls. The weight per half roof element is 70*4,5*1,2=380 kg. The surface of a wall column is 2 sides*260 depth*28 thickness=. This means that the compression force is 380*9,81/14560=0,26 N/mm². This is below the maximum compression force of 17,4 N/mm².

design moisture performance

Moisture and temperature conditions are calculated for worse case scenario.

inside temperature 20 ^oC

inside relative humidity 60%

outside temperature -10 ^oC

outside relative humidity 50%

To control relative humidity during high outside relative humidity, a vapour barrier around the construction could be helpful. Food industry uses bee wax coatings to improve the freshness duration.

The same wax layer on the inside and outside will trap the moisture with condensation as result.

A solution is to apply a thicker wax layer on the inside to lower the vapour pressure in the construction and insulation.

Rtot=0,04+0,06+0,06+5,00+0,06+0,10+0,13=5,45 m²K/W

Q=30/5,45=5,4 W/ m²

Tis= 20-0,13*5,5=19,3 ^oC -> Pio.max=2240 Ps

Tloam= 20-(0,13+0,1)*5,5=18,7 ^oC -> Ploam.max=2175 Ps

Twax= 20-(0,13+0,1+0)*5,5=18,7 ^oC -> Pwax.max=2175 Ps

Tflange= 20-(0,13+0,1+0,06)*5,5=18,4 ^oC -> Pweb.max=2117 Ps

Tstraw= 20-(0,13+0,1+0,06+5)*5,5= -9,1 ^oC -> Pweb.max=281 Ps

Tupperflange= -10+(0,04+0,06+0)*5,5= -9,5 ^oC -> Pweb.max=271 Ps

Tes= -10+0,04*5,5= -9,8 ^oC -> Pweb.max=264 Ps

Figure, Glazer diagram of vapour pressure in construction.

references

Jianying Xu. Development of binderless fiberboard from kenaf core, Journal of Wood Science, springer: Japan, 2006.

Kliger, IR, Pellicane, PJ. Prediction of Creep Properties of Chipboard Used in Stressed-Skin Panels Research scientist, Journal of Testing and Evaluation
Volume 23, Issue 6 , Chalmers University of Technology, 1995.

Ragil Widyorini, Jianying Xu, Takashi Watanabe and Shuichi Kawai. Chemical changes in steam-pressed kenaf core binderless particleboard, Journal of Wood Science. Springer: Japan 2005.

[week 18] extruded kenaf design

An animation of the stressed skin panel design: