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Automotive composites: Thermosets for the fast zone Epoxies continue to be developed for faster cure to meet automotive production rates. By Sara Black / Technical Editor » There are some realities of life that you can’t change. Taxes, for one. Another is that an automotive supplier must have the ability to produce a composite part in a minute, or at least in minutes — not the hours or days that has been the norm for composites in most other industries. The part-per-minutes goal is a hurdle a few composites fabricators have cleared, and many more are involved in development efforts, with OEM or Tier partners. Although the value of thermoplastics for fast automotive production is well established, new versions of thermoset epoxies are proving to process nearly as quickly. But, that said, partper-minute cure demands are taking epoxies into unknown territory, and not all parameters are well understood yet, says automotive industry consultant Gary Lownsdale of Trans Tech International (Loudon, TN, US), formerly the chief technology officer at Plasan Carbon Composites (Wixom, MI, US). Pushing the limits Fast-cure resins go hand in hand with speedy processing. Currently, the fastest processing methods for thermoset composites include resin transfer molding (RTM), high-pressure RTM (HP-RTM), wet compression molding — in which Epoxies to keep up with fast HP-RTM This high-pressure RTM equipment in use at specialist vehicle manufacturer Penso Consulting Ltd. in the UK is molding parts with Cytec’s fast-cure epoxy, XMTM710. Source | Cytec Industries Industrial Materials 46 SEPTEMBER 2015 CompositesWorld
“Snap-Cure” Epoxies NEWS dry reinforcements are wet out with a resin and quickly transferred to a hot compression press — and prepreg compression molding, with and without a vacuum assist (see “Learn More,” p. 51). Plasan Carbon Composites uses a fast compression molding technology called RapidClave that incorporates fast mold heating with hot oil. Overmolding of thermoset parts by injection molding methods can be included as well, for hybrid part approaches. Automotive composite suppliers are for the most part focusing on epoxy, because of its superior adhesive strength and modulus, minimal creep, high toughness and good fatigue performance. (Snap-cure polyurethanes are another option, and can provide strength similar to epoxy, but are not covered here.) Resin chemists have gone far beyond conventional autoclavable aerospace epoxies, which were formulated for stable storage and long out times. To achieve the very low void content aerospace parts must have, those systems require temperature ramps, with dwells, to reduce viscosity and induce flow under slowly increasing pressure in order to remove volatiles and mitigate thermal stress. In sharp contrast, the cure technology of fast-cure epoxies has been greatly accelerated by changing the “protonation” or catalytic amine reaction at the terminal carbon atom sites with proprietary additives, which results in a “thermolatent” system — that is, one that exhibits very low viscosity for a specified length of time, delaying the onset of cure and allowing easy flow to fully wet out the fiber reinforcement, coupled with fast reaction with the hardener as process temperature reaches a specific target. Table 1 summarizes key information for the fast-cure epoxy resin products reviewed for this article. Lownsdale asserts that while a 30-second cure sounds great, there is much to be considered before actually making parts: “All of the process parameters need to be taken into account, as to how you achieve your part T g , to ensure the resin is compatible with your process.” In addition to the degree of crosslinking, he also points out that little is known about “dynamic viscosity,” that is, how does the resin viscosity change under all of the temperature and pressure conditions of the process: “This is a critical issue, and there’s a lot of confusion in the industry, with very little information available because standardized testing is lagging behind the new processes.” He cautions composite processors to investigate these unknowns with their resin suppliers, to ensure that produced parts match OEM requirements and expectations. So how does one choose a snap-cure resin and determine whether or not it’s a good fit with a process? It comes down to working with a supplier, trusting them to guide you through a selection process and asking the right questions, says Lownsdale. CW checked in with the makers of snap-cure epoxy, for liquid molding and prepreg processing, for their perspectives on the snap-cure trend, their fast-cure products, processing considerations and where the autocomposites sector is going. Peter Cate, global strategic marketing manager for composite structures at Dow Automotive Systems (Horgen, Switzerland) says that snap-cure is triggered by the material’s exposure to tool temperature, but adds, “Snap cure alone is relatively easy to achieve but is useful only if the resin has fully infused the Fast cure for the i3 Huntsman associates examine an automotive part made with trademarked Araldite LY 3585/Aradur 3475 fast-curing epoxy system in the Huntsman composites laboratory. The epoxy product is used to produce the BMW i3 production car, in a high-pressure resin transfer molding (RTM) process, and the company says that second-generation versions are now available. Source | Huntsman Advanced Materials Trials for prospective commercial product Dow Automotive’s in-house Composite Development Center in Switzerland is equipped with a high-pressure RTM machine used for development programs for its VORAFORCE fast-curing epoxy. Source | Dow Automotive CompositesWorld.com 47
Page 1 and 2: Part-per-Minute Epoxies: THERMOSETS
Page 3 and 4: TABLE OF CONTENTS SEPTEMBER 2015 /
Page 5 and 6: The cutting edge technology found i
Page 8 and 9: PERSPECTIVES & PROVOCATIONS Outer s
Page 10 and 11: BUSINESS INDEX CW Business Index at
Page 12 and 13: TRENDS The fabled Oshkosh Fly-in, f
Page 14 and 15: TRENDS AEROSPACE Automating inserts
Page 16 and 17: TRENDS Vacuum Test Unit Compact, li
Page 18 and 19: TRENDS MONTH IN REVIEW Notes on new
Page 20 and 21: TRENDS AUTOMOTIVE Quilted Stratum P
Page 22 and 23: TRENDS AEROSPACE Huge acquisitions
Page 24 and 25: TRENDS ENERGY US wind energy: Found
Page 26 and 27: TRENDS AEROSPACE NASA to enlist rob
Page 28 and 29: TRENDS Laser chemical vapor deposit
Page 30 and 31: WORK IN PROGRESS Fused-particle too
Page 32 and 33: WORK IN PROGRESS Sealing the frame,
Page 34 and 35: WORK IN PROGRESS they could do furt
Page 36 and 37: WORK IN PROGRESS VOC reduction stra
Page 38 and 39: WORK IN PROGRESS for lowering overa
Page 40 and 41: WORK IN PROGRESS but slightly worse
Page 42 and 43: Fan Blade High-Pressure Compressor
Page 44 and 45: MARKET OUTLOOK FIG. 3 Thrust revers
Page 46 and 47: MARKET OUTLOOK feature, made at Air
Page 50 and 51: FEATURE / AUTOMOTIVE COMPOSITES Fas
Page 52 and 53: FEATURE / AUTOMOTIVE COMPOSITES (IA
Page 54 and 55: Mubea Carbo Tech: High-quality auto
Page 56 and 57: PLANT TOUR FIG. 1 Monocoque tubs vi
Page 58 and 59: PLANT TOUR FIG. 5 Parts, parts ...
Page 60 and 61: PLANT TOUR FIG. 6 CF + steel Mubea
Page 62 and 63: PLANT TOUR Read this article online
Page 64 and 65: INSIDE MANUFACTURING Composites upg
Page 66 and 67: INSIDE MANUFACTURING 1 Tubular poly
Page 68 and 69: INSIDE MANUFACTURING environmental
Page 70 and 71: CALENDAR Composites Events Sept. 8-
Page 72 and 73: APPLICATIONS COMPOSITE BRACKETS FOR
Page 74 and 75: NEW PRODUCTS Product Showcase » MA
Page 76 and 77: NEW PRODUCTS » TESTING & MEASURING
Page 78 and 79: MARKETPLACE MANUFACTURING SUPPLIERS
Page 80 and 81: FOCUS ON DESIGN Automotive front ax
Page 82 and 83: FOCUS ON DESIGN Simplified design I

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