Design and processing of composite products from renewable resources can they compete with non-renewable composites?

Transcription

1 Design and processing of composite products from renewable resources can they compete with non-renewable composites? B. Nyström 12/6/07 Swerea SICOMP AB,Box 271, Piteå, Sweden 1/3/08

2 The Swerea Group Swerea IVF Production efficiency, industrial product design and ecodesign. Process- and material development for textils, polymers, metalls and ceramics. Swerea KIMAB develops and improves solutions for materials Research within corrosion and materials research. Swerea MEFOS creates, refines and conveys research results in process metallurgy, heating, metalworking, the environment and energy technology. Swerea SICOMP focused on composite materials Materials Science, Process Science & Manufacturing and Structural Design Swerea SWECAST focused on casted materials, processes, products and environmental- and energy efficiency Key numbersl Non-profit organization 530 employees 630 Mkr turnover 500 member companies industrial customers Presentation 11/18/2013 av Swerea Presentation koncernen av Swerea SICOMP 2

3 What we do Recycling Characterization of processability and materials selection Swerea SICOMP started composite research 1989 Biobased composites 1997 Impact and Crash Damage tolerance and fatigue Product design, Manufacture and testing Selection of manufacturing Methods & Process modelling 3

4 Why we work with biobased composites World population reached 7 billions 2011 Average economical growth rate 3% per year doubling time every 23 years Climate change caused by the use of fossil resources End of cheap oil 2008 (IEA World Energy Outlook report 2008) Unconventional oil has even more detrimental environmental effects and lower energy return We must find alternative energy sources We also need new material options especially for lightweight designs for the transport sector Biobased composites is one such material option We are here This slope is known Unknown slope of this side of the curve 11/18/2013 4

5 Application areas for Biobased Composites Transportation Construction Furniture Sports 11/18/2013 Presentation av Swerea SICOMP 5

6 Comparison natural fibre vs glass fibre Processing is often very similar to processing of glass fibres Density is lower Good specific strength and high stiffness They are spun and twisted Can not be packed to as high fibre volume fractions as glass fibres Composite strength and stiffness depend on fibre volume fraction Can be compensated by thickness but in many applications, to be a competitive material alternative, weight of the product should not increase 6

7 Comparison biobased resin - fossil oil based resins Chemicals to make resin can be extracted from forest, agricultural waste etc. as well as from oil A biobased epoxy should still be an epoxy - properties should be very similar (goes for any biobased resin and its non-renewable counterpart) Tests of several new biobased resins show that they are processable and have similar properties to nonrenewable resins Room for improvement still 7

8 Design considerations Trailer door solve an existing problem using biobased composites Comparison of a biobased composite with an optimised glass fibre composite sandwich Comparison of a biobased composite to steel 8

9 Properties of Bio-Based Composite used in the following examples Flax and renewable and biobased epoxy resin Stiffness is less than half for flax composites Strength is less than 1/3 for flax Density is 2/3 for flax composites Fibre content accounts for 74% of the difference in stiffness and 62% in strength

10 Design calculations GF/epoxy Flax/Epobiox Factor tension (area free) bending beam, shape specified, area free (a) bending beam, width specified, height free (b) bending beam, height specified, width free (c) E/ρ σ/ρ E 1/2 /ρ σ 2/3 /ρ E 1/3 /ρ σ 1/2 /ρ E/ρ σ/ρ a b c

11 Design considerations The optimal structural application for these biobased composites is where bending is the primary type of loading and where height of the design is not restricted

12 Example: Trailer door solve an existing problem using biobased composites? Initial design: Glass fibre laminate/veneer/styrofoam/veneer/glass fiber laminate Thickness max 40 mm, weight of the structure is 17 kg/m 2 Deflection is too large when loaded, 50 mm in the centre-should be max 20 mm Can biobased flax laminates be used to fix this? Requirements: Max thickness, 40 mm, should be maintained Max 20 mm deflection in the center of the door when it is filled Should not increase in weight

13 Method Assumption: the load case can be estimated by 3-point bending test Test of the old design to find its material properties by back calculation Measured mechanical properties of flax laminates are used for calculation of the deflection for a sandwich with biobased skins

14 Mechanical models for deflection For a symmetric sandwich beam (both skins have the same thickness and material properties), the deflection (δ) can be expressed with the following equation: δ = δ b + δ s = (F L 3 /D) (1/24) + (F L/S) (1/4) where: D=E f t f d d/2 + E f t f3 /6 F is the force per mm L is the length between supports E f is the modulus of the composite G c is shear modulus of the core t f is thickness of the composite t c is core thickness d is t f + t c S = G c d 2 /t c

15 Deflection (mm) Weight (kg/m 2 ) Deflection and weight vs skin thickness sandwich with flax laminates Laminate thickness 12 (mm) With 15 mm flax skins deflection <20 mm is reached Clearly heavier structure than todays design

16 Deflection [mm] Weight (kg/m2) Deflection and weight vs total thickness with flax skins 6,5 mm thick , , , , , , , ,3815 Total thickness (mm) By increasing core thickness the weight is almost unaffected while the deflection rapidly decreases Total thickness >46 mm meets deflection criteria with each flax skin 6,5 mm

17 Conclusions from this example Modulus of initially used skins is not high enough to meet design criteria - 20 mm deflection, with maintained total thickness Modulus of flax skin is almost twice as high Design criteria can be met with thick flax skins but this will make structure much heavier, 15mm skins and 10mm core Design criteria can easily be met by increasing core thickness with very little change of weight Current skins, core 47 and total thickness 60 mm Flax skins, core 35 total thickness 48 mm

18 Compared to optimised design In the first example design was not optimised initially What if a glass fibre sandwich panel is optimised already? Can biobased skins replace glass fibre if redesign is allowed? Competitive in both mechanical properties and weight? 18

19 Design calculations in sandwich structure : bending beam, specified width (50 mm), free height (=thickness) 0.9 mm 1.1 mm Glass/Epoxy 0.37 kg 50 mm +10% weight Flax/Epobiox 0,41 kg 70 mm Sandwich in 3P-bending, load 1000 N, length 1m, rectangular cross-section, deflection = max 2% of L Difficult to compete with glassfibre in weight

20 Compared to steel design Initial design: Steel New design: Biobased composites 20

21 Composite Design Integrated sides, back and base support Cassettes are load bearing. Side supports to locate the cassettes. Thickness of the laminates is larger than steel thickness Designed for epobiox and flax. Manufacturing- vacuum infusion: low tool cost, low series

22 Raw materials - Steel verses Flax Weight saving for the whole constraction is 18% with biobased composite

23 Conclusion Can fully bio-based composites compete with glass fibre composites a) in terms of mechanical performance? Yes, if the load case is bending and the weight doesn t matter b) in terms of sustainability and environmental impact? Yes, they are made from renewable raw material, opposite to finite, therefore more sustainable c) In terms of light weight constructions? Not really, fibre volume fraction limits utilisation of their properties For high performance light weight applications renewable continuous fibres are needed, for example: Carbon fibres from lignin Regenerated cellulose for structural applications Development of biobased materials; to be continued

24 Acknowledgements The research was funded by the Woody project, and the Anacompo project

25 Thank you for your attention! Questions? 12/6/07 1/3/08