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TRANSCRIPT
Hybrid Long Fiber Thermoplastic Composites:
A Perfect Blend of Performance and Cost
Eric Wollan Technology Director
Abstract
►Mass reduction is a technique widely used among automotive OEMs to meet increased fuel economy regulations. Lightweight carbon fiber reinforced composites are well known for their superior performance, but their higher cost presents a barrier to wide spread adoption. Hybrid long fiber thermoplastic composites which blend carbon fiber with other fibers, such as glass, provide a stepped approach to decreasing mass and cost while providing opportunities to optimize performance with different fiber mix ratios. Their synergistic balance of strength, toughness, and cost are examined as a method to expand the use of long fiber composites in automotive applications.
Overview
►Current state of long fiber composites – Long glass fiber – Long carbon fiber
►Methodology for hybrid trials
►Hybrid long glass + carbon fiber data – Polypropylene – Polyamide 6/6 – Rigid polyurethane
►Analysis, observations, & applications
Long Glass Fiber
►LGF/PP synonymous with semi-structural automotive components – Has become a commodity material
►Can be pultruded into any polymer to obtain metal replacement performance – Best performance boost achieved with semi-
crystalline polymers
►Glass is strong yet flexible fiber – High aspect ratio of long glass fiber facilitates
energy transfer, increasing durability rather than stiffer material becoming brittle
– Durability retained at both low and elevated temperatures
Long Carbon Fiber
►Carbon fiber synonymous with high performance – Widely adopted within aerospace market
►Top choice for mass reduction/lightweighting – 30% lighter than glass fiber composites – 50% lighter than aluminum
►Cost to entry barrier – Steep price for those used to working with
glass fiber materials
► “High tech” perception – Gives non-industrial products a marketing
advantage with consumers
Hybrid Long Glass + Carbon Fiber
12 mm hybrid long glass+carbon fiber composite pellets
Hybrid Long Glass + Carbon Fiber
►Continuous glass+carbon fiber roving combined in pultrusion process to form single pellet hybrids – More uniform distribution of fiber types than post blending
materials during injection molding
► Initial trials indicated long glass+carbon fiber hybrids could produce results that bridged the performance gap between using either fiber type individually – Glass fiber contributed toughness – Carbon fiber contributed stiffness and strength
►Hybrids could lower the cost barrier to adopting carbon fiber’s higher performance benefits
Methodology
►Further trials in additional polymers – Polypropylene – Polyamide 6/6 – Rigid polyurethane
►Can substituting weight % of carbon fiber in a glass fiber LFT formulation expand its performance envelope?
►Can adding volume fraction of glass fiber to a carbon fiber LFT composite provide similar performance at lower cost?
Hybrid Polypropylene Data
► Percentage increase graphed, lowest value for each property equivalent to 100%
Hybrid Polypropylene Data
LGF50 PP
NAT Δ
LCF20/ LGF30
PP BLK
Δ LCF20
PP NAT
LCF40 PP
NAT
Cost Multiplier 1.0 4.3 4.3 7.2
Density 1.33 96% 1.27 127% 1.00 1.14
Tensile Strength 145 MPa 88% 127 MPa 94% 135 MPa 148 MPa
Tensile Modulus 11.2 GPa 155% 17.3 GPa 166% 10.4 GPa 21.1 GPa
Flexural Strength 223 MPa 89% 198 MPa 128% 155 MPa 227 MPa
Flexural Modulus 9.6 GPa 133% 12.8 GPa 162% 7.9 GPa 15.3 GPa
Un-Notched Impact 961 J/m 67% 641 J/m 126% 507 J/m 705 J/m
► Δ glass fiber to hybrid fiber, same total fiber content ► Δ hybrid fiber to carbon fiber, same total carbon fiber content
Hybrid Polypropylene Analysis
►Substituting carbon for glass fiber – Modulus increases – No significant benefit to other properties in PP – Increased cost 4X
►Adding glass to carbon fiber – Stiffness and toughness boosted – Negligible impact on cost – Weight savings impacted
Hybrid Polyamide 6/6 Data
► Percentage increase graphed, lowest value for each property equivalent to 100%
Hybrid Polyamide 6/6 Data
LGF50 PA66 BLK
Δ
LCF20/ LGF30 PA66 BLK
Δ LCF20 PA66 NAT
LCF50 PA66 NAT
Cost Multiplier 1.0 3.7 3.5 6.2
Density 1.57 96% 1.51 123% 1.22 1.37
Tensile Strength 212 MPa 127% 270 MPa 102% 266 MPa 309 MPa
Tensile Modulus 16.2 GPa 191% 31.0 GPa 165% 18.8 GPa 40.1 GPa
Flexural Strength 302 MPa 145% 439 MPa 119% 368 MPa 491 MPa
Flexural Modulus 13.6 GPa 160% 21.8 GPa 147% 14.8 GPa 27.6 GPa
Un-Notched Impact 1,009 J/m 104% 1,052 J/m 137% 769 J/m 881 J/m
► Δ glass fiber to hybrid fiber, same total fiber content ► Δ hybrid fiber to carbon fiber, same total carbon fiber content
Hybrid Polyamide 6/6 Analysis
►Substituting carbon for glass fiber – Increased modulus and strength – Slight decrease in density – Cost multiplier increased by almost 4X
►Adding glass to carbon fiber – Increased modulus and strength – Impact strength raised – Cost multiplier is negligible
Hybrid Rigid Polyurethane Data
► Percentage increase graphed, lowest value for each property equivalent to 100%
Hybrid Rigid Polyurethane Data
► Δ glass fiber to hybrid fiber, same total fiber content ► Δ hybrid fiber to carbon fiber, same total carbon fiber content
LGF40 TPU BLK
Δ
LCF20/ LGF20
TPU BLK
Δ LCF20
TPU NAT
LCF40 TPU NAT
Cost Multiplier 1.0 2.8 2.7 3.8
Density 1.51 95% 1.44 113% 1.28 1.38
Tensile Strength 192 MPa 129% 248 MPa 133% 187 MPa 294 MPa
Tensile Modulus 11.8 GPa 164% 19.3 GPa 139% 13.9 GPa 27.9 GPa
Flexural Strength 271 MPa 132% 358 MPa 143% 251 MPa 438 MPa
Flexural Modulus 9.9 GPa 161% 15.9 GPa 150% 10.6 GPa 22.7 GPa
Un-Notched Impact 1,140 J/m 86% 983 J/m 142% 696 J/m 1,019 J/m
Hybrid Rigid Polyurethane Analysis
►Substituting carbon for glass fiber – Strength and modulus increased – Toughness slightly reduced – Almost 3X increase in cost
►Adding glass to carbon fiber – Modulus and strength boosted – Durability improved – Cost to performance increase is negligible
Observations
►Long glass + carbon fiber hybrids yielded better property increase in polyamide and polyurethane than in polypropylene – Might be result of better polymer-to-fiber bonding
►Other polypropylene LFT hybrid formulations containing less carbon fiber provide better ratio of cost to performance increase
►Continue trials with higher performance grades of glass fiber and other fiber types (basalt) to determine benefit
Observations
►Other hybrid LFT glass + carbon PP formulations LCF5/ LGF15
PP NAT
LCF10/ LGF20
PP NAT
LCF10/ LGF30
PP NAT
LCF15/ LGF25
PP NAT
LCF20 PP
NAT
Fiber Content 20% 30% 40% 40% 20%
Cost Multiplier 2.4 2.8 3.1 4.3 4.3
Density 1.03 1.10 1.19 1.17 1.00
Tensile Strength 112 MPa 136 MPa 145 MPa 128 MPa 135 MPa
Tensile Modulus 6.7 GPa 9.7 GPa 14.5 GPa 14.1 GPa 10.4 GPa
Flexural Strength 152 MPa 184 MPa 219 MPa 197 MPa 155 MPa
Flexural Modulus 4.8 GPa 7.0 GPa 10.0 GPa 10.4 GPa 7.9 GPa
Un-Notched Impact 513 J/m 555 J/m 651 J/m 732 J/m 507 J/m
Applications
►Performance increase of LFT hybrids will facilitate more metal-to-plastic conversions to reduce weight without moving to higher-cost all-carbon fiber composites to obtain necessary performance
►Substitute LFT hybrids for short glass engineering polymers – Cost offset by reduced material use (thinner wall
sections) and associated weight savings
►Under-hood components
►Powertrain applications
Development Philosophy
►Don’t simply substitute one material for another ► Integration of design, material, and process required to
maximize benefit of material change
Successful Integration
Injection Molding Process
Part & Tool Design
Long Fiber Material
SPE ACCE Notes
►Presentation time slot 30 minutes including introduction and post discussion
►Add more data if rehearsals indicate more time available? ►Thursday, September 10th @ 10:30 a.m.