Rome 15 – 17 April 2009 Scarponi Claudio * Pizzinelli Corrado Sebastiano * Sonia Sánchez-Sáez **...

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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 onInnovative Natural Fibre Composites for Industrial Application

** Universidad Carlos III de Madrid

Introduction: Natural Fibers

2Impact 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

Applications and possible market

3Impact load behaviour of RTM(Resin Transfer Moulding) hemp fibre composite laminates

• Radome• Interiors (seats, caps, tables…)• Baggage container• Non primary structural applications

in general

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

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

Reinforcement

“plain weave” hemp fabric (National Canapificio Linificio-Spa of Verona)

Linear mass density (average) [Tex] 71,7

Pretentioning strength [cN/Tex] 0,5Density (average) [gr/cm3] 1.7Maximum strength (literature) [MPa] 590±150Young Modulus (literature) [GPa] 18 ±4Elongation at break in traction (literature) [%] 4±0,3Specific areal weight [gr/m2] 244Price [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

Matrix

Epoxy Resin

SR1710

Curing Catalyst

SD8824

SR1710/SD8824

Mix 100ml/28mlViscosity [mPa*s] 20 ºC25 ºC

1300800

205120

Density [g/cm³] 20 ºC

1,152 0,942 1.106 *

(*calculated data)

It has been chosen an epoxy resin, because of its excellent mechanical properties and in particular for the resistance to

interlaminar shear

RTM & PROCESS

The panels fabrication has been performed at the Centro Sviluppo Materiali laboratories, with a Plastech T.T. machine.

COMMAND CONSOLE

OMOGENIZATOR

• command console• omogenizator (the

degassing is performed here only for the first panel)

• mold

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

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 reactions2. 24h at 40 º C

Hemp-Glass comparison

2 hemp threads

Glassfiber fabric

Panel 1

PANEL 1. (12 plies)Resin Inlet

• bad wetting• non uniform

resin distribution

• voids

Resin Trap and Improved degassing

Degassing; it is visible the typical “foam”The “resin trap” prevents the excess resin flow to go back into the pump

Also the maximum pressure has been decreased

Panel 2 & comparison

Resin Inlet

PANEL 2. (14 plies)

Resin Inlet

PANEL 1. (12 plies)

Properties and comparison

PANEL PROPERTIES

Panel 1

Base RTM%

Panel 2

Enhanced RTM

Total Weight (g) 880 - 1084,5 -

Fibers weight (g) 367,7 42% 520 48%

Resin weight (g) 512.3 58% 564,5 52%

Area (cm²) 40*33=1320 - 40x40 = 1600 -

Thickness (mm) 5,1 - 5,1 -

Volume (cm³) 673,20 - 816 -

Density (panel) (g/cm³) 1.307 - 1.329 -

V resin (cm³) 463.18 68.8% 510.37 62.5%

V fibers (cm³) 210.02 31.2% 305.73 37.5%

N. of fabric plies 12 _ 14 _

Resin Inlet point

Tensile and flexural tests (4PBT)

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.

Tensile test

0,00 0,50 1,00 1,50 2,00

strain %

Tensile test: stress-strain curve

Table 5:

MATERIAL

Max strength

Young Module

E (GPa)

Rupture load

Strain

(rupture) %

Hemp/Epoxy 93,77±3,22 6,10±0,17 9542,50 1,9±0,2Impact load behaviour of RTM

(Resin Transfer Moulding) hemp fibre composite laminates

Flexural test

-25-20-15-10-50

Displacement (mm)

Since the trend is not linear and the slope of the curve decreases, rupture is probably due to shear stresses.

Table 6Flexural Resistance(MPa)

Flexural Modulus(GPa)

Max Load(N)

Average 145±9,4 11,87±1,65 416,33±22,6variation coefficient 6,48 (%) 13,9 (%) 5,43 (%)

Impact test

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)

5 10 15

Speed (m/s)

1.59 2.25 2.75

Impact

Force-time curves. With the help of the table is possible to distinguish:

•Incipient damage time•Displacement at this time

ImpactEnergy

Incipient damage

time(average)

Var. Coeff.

Displ.(average)

Var.Coeff.(%)

5 2.02 4.9 2.41 3.6

10 1.15 1.4 2.31 1.3

15 0.97 1.1 2.47 0.95

Impact 2

Force-deflection average curves. With the help of the table is possible to distinguish:

•Max displacement•Instant of max displacement

ImpactEnergy

MaxDispl.[mm]

Var.Coeff.(%)

Max displ. Time [ms]

Max Force

Var.Coeff.(%)

5 2.79 2.8 3.10 2689 1.910 4.58 2.7 3.64 2989 0.815 6.44 2.8 4.37 2996 4.1

Energies involved

absorbedelasticimpact EEE

dispdamageabsorbed EEE

dispdfdmnindentatioelasticimpact EEEEEE

Eabsorbed, 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 (Edamage ) and energy absorbed by the system by various means such as vibrations, heat, anelastic behaviors, etc. (Edisp):

Impact 3

Energy-time curve

red Eimpact,

Green E absorbed

black E elastic

0 2 4 6 8 10 12

Time (ms)

Energy History

(Santulli - STUDY OF IMPACT HYSTERESIS CURVES ON E-GLASS REINFORCED POLYPROPYLENE LAMINATES)

HYSTERESIS

ImpactEnergy

Energyabsorbed

Var. coeff. (%)

En. absorbed/impact En.

5 2.76 0.29 0.55210 7.26 0.63 0.72615 11.4 0.01 0.76

ImpactEnergy[J]

A1 [J]

damping ratio

linear stiffness[KN/mm]

Load drop[N]

5Average 2.547 0.211 0.755 0.351 1.175 75VC (%) 2.1 25.3 19.3 20.6 4.7 6.6

10Average 3.409 3.861 2.224 0.837 1.229 153VC (%) 2.6 1.7 1.1 1.4 3.2 6.6

15Average 3.748 7.685 3.020 0.936 1.240 192VC (%) 1.5 1.1 5.1 1.9 1.2 5.5

Specimen code Lay-upHand lay-up

Thickness(mm)

Fiber Volume (%)

Density(g/cm3)

H14 14 Hemp 5.1 38 1.33

J10 10 Jute 8,0 52 1.05

V10 10 E-Glass 300 4,00 35 1.55

JV [3V/2J/1V/2J/6V] 5,0 55 1.33

JA-E 300 [4V/2J/1V/2J/4V] 5,0 55 1.32

JB-E 600 [2V/2J/1V/2J/2V] 5,0 53 1.36

JX-E 600 [1V/2J/1V/2J/3V] 5,0 53 1.35

same geometries, impact energy and boundary conditions

Comparison with jute/vynilester hybrids:

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)

H14 5.1 38 2.69 2.99 2.92 3.00 7.26 11.43J10 8,0 52 2.70 4.10 3.60**V10 4,00 35 3.50 4.70 5.60 4.880 8.480 11.9JV 5,0 55 4.00 6.00 6.70 4.550 7.880 12.45JA-E 300 5,0 55 4.50 5.00 6.20 4.950 8.200 12.1

JB-E 600 5,0 53 4.20 5.60 6.4 4.375 8.880 12.45JX-E 600 5,0 53 4.10 4.90 6.1 4.380 7.890 11.7

V: glass fiber; J: jute fibers H: Hemp fibers **perforation without trepassing

Same MASS, geometries, impact energy and boundary conditions

Impact side

Back side

ates 5J

BACKLIGHT: 5J impacted specimens (10 x 10 cm)

Digitally sharpened and “inverted”

Original

Impact Energy (J) 5 10 15Delaminated area (mm2) 332 863 1380Standard Deviation (mm2) 108 151 161Variation Coefficient (%) 32,45 17,49 11,69

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.

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

Thank you for your attention!

Scarponi ClaudioPizzinelli Corrado Sebastiano *

Sonia Sánchez-SáezEnrique 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

Rome 15 – 17 April 2009 Scarponi Claudio * Pizzinelli Corrado Sebastiano * Sonia Sánchez-Sáez **...

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