1. Rome 15 – 17 April 2009 Scarponi Claudio * Pizzinelli Corrado Sebastiano * Sonia Sánchez-Sáez ** Enrique Barbero ** * Sapienza Università di Roma Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates Second International Conference on Innovative Natural Fibre Composites for Industrial Application ** Universidad Carlos III de Madrid

2. Introduction: Natural Fibers 2 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates Vantages: Good specific mechanical properties Low cost, low weight, low tool wear “Bio-friendly”, non toxic… Thermal and electrical insulation Disadvantages: Properties depend from many factors Defects and irregularities Water absorption (swelling and problems…) Fiber/matrix adhesion… Natural fibres might be a realistic alternative to glass fibres reinforced composites

3. Applications and possible market 3 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates Radome Interiors (seats, caps, tables…) Baggage container Non primary structural applications in general

4. Aims of this work Investigate the behavior of composites laminates reinforced by hemp fabric, processed by RTM Improve the RTM process determine the effect of damages caused by low velocity impact loads Compare the results with literature 4 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

5. Reinforcement 5 “ plain weave” hemp fabric (National Canapificio Linificio-Spa of Verona) Linear mass density (average) [Tex]71,7 Pretentioning strength [cN/Tex]0,5 Density (average) [gr/cm 3 ]1.7 Maximum strength (literature) [MPa] 590±150 Young Modulus (literature) [GPa] 18 ±4 Elongation at break in traction (literature) [%] 4±0,3 Specific areal weight [gr/m 2 ]244 Price [euro/ meter2]12 From previous studies alkalinization with sodium hydroxide NaOH 1% wt did not produce convenient performance increase Fabric has not been chemically treated

6. Matrix 6 Epoxy Resin SR1710 Curing Catalyst SD8824 SR1710/SD8824 Mix 100ml/28ml Viscosity [mPa*s] 20 ºC 25 ºC 1300 800 8686 205 120 Density [g/cm³] 20 ºC 1,1520,9421.106 * (*calculated data) It has been chosen an epoxy resin, because of its excellent mechanical properties and in particular for the resistance to interlaminar shear Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

7. RTM & PROCESS 7 The panels fabrication has been performed at the Centro Sviluppo Materiali laboratories, with a Plastech T.T. machine. COMMAND CONSOLE OMOGENIZATOR MOLD command console omogenizator (the degassing is performed here only for the first panel) mold Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

8. 8 Mold & Countermold 400x400 mm Electrically heated The resin, after being aspired from the omogenizator, is degassed On the mold there are some little holes through which is aspired the resin in excess Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

9. 9 Injection & polymerization 0°/90° fabric disposition Vacuum Degassing & Resin injection at 0.5 bar After having wetted half tissue, pressure is increased and kept to 3 bar Polymerization sequence 1.6h at room temperature, to reduce risk of reactions 2.24h at 40 º C Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

10. Hemp-Glass comparison 10 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates 2 hemp threads Glassfiber fabric zoom

11. Panel 1 11 PANEL 1. (12 plies) Resin Inlet bad wetting non uniform resin distribution voids Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

12. Resin Trap and Improved degassing 12 Degassing; it is visible the typical “foam” The “resin trap” prevents the excess resin flow to go back into the pump Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates Also the maximum pressure has been decreased

13. Panel 2 & comparison 13 Resin Inlet PANEL 2. (14 plies) Resin Inlet PANEL 1. (12 plies) Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

14. 14 Properties and comparison PANEL PROPERTIES Panel 1 Base RTM % Panel 2 Enhanced RTM % Total Weight(g)880-1084,5- Fibers weight(g)367,742%52048% Resin weight(g)512.358%564,552% Area(cm²)40*33=1320-40x40 = 1600- Thickness (mm)5,1- - Volume (cm³)673,20-816- Density (panel)(g/cm³)1.307-1.329- V resin(cm³)463.1868.8%510.3762.5% V fibers(cm³)210.0231.2%305.7337.5% N. of fabric plies12_14_ Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates Resin Inlet point

15. Tensile and flexural tests (4PBT) 15 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates Tensile: 5 specimens tested on a Zwick machine at room temperature, with a load cell of 250 kN, following normative ASTM D3039 (D638 for test on resin) 4PBT: 6 specimens tested at room temperature, with a load cell of 200kN, following normative ASTM D790-86.

16. Tensile test 16 Table 5: MATERIAL Max strength (MPa) Young Module E (GPa) Rupture load (N) Strain (rupture) % Hemp/Epoxy93,77±3,226,10±0,179542,501,9±0,2 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

17. Flexural test 17 Since the trend is not linear and the slope of the curve decreases, rupture is probably due to shear stresses. Table 6 Flexural Resistance (MPa) Flexural Modulus (GPa) Max Load (N) Average145±9,411,87±1,65416,33±22,6 variation coefficient6,48 (%)13,9 (%)5,43 (%) Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

18. Impact test 18 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates Square specimens 100x 100 mm have been utilized for the impact test (3 for each energy level) bounded with a clamping (ASTM D5628-96, ASTM D5428-98th). The hemispherical head impacter has a mass of 3.966 Kg and a diameter of 12.7 mm Energy level (J) 51015 Speed (m/s) 1.592.252.75

19. Impact 19 Force-time curves. With the help of the table is possible to distinguish: Incipient damage time Displacement at this time Impact Energy [J] Incipient damage time (average) [ms] Var. Coeff. (%) Displ. (average) [mm] Var. Coeff. (%) 52.024.92.413.6 101.151.42.311.3 150.971.12.470.95

20. Impact 2 20 Force-deflection average curves. With the help of the table is possible to distinguish: Max displacement Instant of max displacement Impact Energy [J] Max Displ. [mm] Var. Coeff. (%) Max displ. Time [ms] Max Force [N] Var. Coeff. (%) 5 2.792.83.1026891.9 10 4.582.73.6429890.8 15 6.442.84.3729964.1

21. Energies involved 21 E absorbed, is the asymptotic Energy value and represents the energy dissipated in fracture mechanism. It can be divided in two major type of contributions: energy expended to generate the damage (E damage ) and energy absorbed by the system by various means such as vibrations, heat, anelastic behaviors, etc. (E disp ):

22. Impact 3 22 Energy-time curve red E impact, Green E absorbed black E elastic Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

23. 23 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

24. 24 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

25. 25 ( Santulli - STUDY OF IMPACT HYSTERESIS CURVES ON E-GLASS REINFORCED POLYPROPYLENE LAMINATES) HYSTERESIS Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates

26. 26 Impact Energy (J) Energy absorbed (J) Var. coeff. (%) En. absorbed/ impact En. 52.760.290.552 107.260.630.726 1511.40.010.76 Impact Energy [J] A1 [J] A2 [J] A3 [J] damping ratio linear stiffness [KN/mm] Load drop [N] 5 Average 2.5470.2110.7550.3511.17575 VC (%) 2.125.319.320.64.76.6 10 Average 3.4093.8612.2240.8371.229153 VC (%) 2.61.71.11.43.26.6 15 Average 3.7487.6853.0200.9361.240192 VC (%) 1.51.15.11.91.25.5

27. 27 Specimen code Lay-up Hand lay-up Thickness (mm) Fiber Volume (%) Density (g/cm3) H1414 Hemp5.1381.33 J1010 Jute8,0521.05 V1010 E-Glass 3004,00351.55 JV[3V/2J/1V/2J/6V]5,0551.33 JA-E 300[4V/2J/1V/2J/4V]5,0551.32 JB-E 600[2V/2J/1V/2J/2V]5,0531.36 JX-E 600[1V/2J/1V/2J/3V]5,0531.35 same geometries, impact energy and boundary conditions Comparison with jute/vynilester hybrids:

28. Specimen code Thick- ness (mm) Fiber Volume (%) Max contact force 5J impact (KN) Max contact force 10J impact (KN) Max contact force 15J impact (KN) Energy absorbed 5J impact (J) Energy absorbed 10J impact (J) Energy absorbed 15J impact (J) H145.1382.692.992.923.007.2611.43 J10 8,0522.704.103.60** V10 4,00353.504.705.604.8808.48011.9 JV 5,0554.006.006.704.5507.88012.45 JA-E 300 5,0554.505.006.204.9508.20012.1 JB-E 600 5,0534.205.606.44.3758.88012.45 JX-E 600 5,0534.104.906.14.3807.89011.7 V: glass fiber; J: jute fibers H: Hemp fibers **perforation without trepassing 28 Same MASS, geometries, impact energy and boundary conditions

29. Impact side 29 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates 5J 10J 15J

30. Back side 30 Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates 5J 10J 15J

31. 31 BACKLIGHT: 5J impacted specimens (10 x 10 cm) Digitally sharpened and “inverted” Original BACKLIGHT: 10J impacted specimens (10 x 10 cm) Digitally sharpened and “inverted” Original

32. 32 Original Digitally sharpened and “inverted” BACKLIGHT: 15J impacted specimens (10 x 10 cm)

33. 33 Impact Energy (J) 51015 Delaminated area (mm 2 ) 3328631380 Standard Deviation (mm 2 ) 108151161 Variation Coefficient (%) 32,4517,4911,69

34. Conclusions and possible future developments An RTM system, has been successfully used with hemp fibers. It has been proven experimentally that process parameters greatly influence the final product The process has been improved with a negligible cost impact. Even if it was not the aim of this paper, further enhancements are possible in order to achieve more improvements such as geometry and number of resin immission holes, pressure-time curves, curing process. Hemp/epoxy composites exhibit good impact properties It is confirmed the hypothesis that it can be possible to start using for secondary structures hemp as a reinforcement alternative to glass. Further studies are needed also to characterize the internal behavior of the material and residual properties. 34

35. Acknowledments Ing. Fulvio Ferraro of the CSM for the RTM process; (CSM: Centro Sviluppo Materiali s.p.a., via di Castel Romano n. 100, cap 00128 Roma.) Ing Teresa Vetere for the resistance tests Prof. Carlo Santulli 35

36. Thank you for your attention! 36 Scarponi Claudio Pizzinelli Corrado Sebastiano * Sonia Sánchez-Sáez Enrique Barbero *Reference author; E-mail: sebarm86@hotmail.com “Sapienza Università di Roma” Impact load behaviour of RTM (Resin Transfer Moulding) hemp fibre composite laminates Dipartimento di Ingegneria Aerospaziale e Astronautica