CompositesWorld
Issue link: https://cw.epubxp.com/i/681810
JUNE 2016 32 CompositesWorld MARKET OUTLOOK market manager, says, "BETAFORCE, depending on the specifc grade, has a modulus varying from 20 MPa to 300 MPa and an elongation as high as 400% for superior energy absorption under dynamic and fatigue loading." Van Herreweghe says that previous grades of BETAFORCE required a primer coat or application of an activator, but the latest grade does not. Although any mold release that remains on the composite parts must be removed prior to bonding, he empha- sizes that BETAFORCE bonds well to composites. After adhesive is dispensed via automated meter/mix machine, cure occurs with application of heat, typically infrared or other rapid method, to more than 80°C for 1-3 minutes to achieve handling strength. Dow Automotive is currently working on expanding the adhe- sive's open time, in combination with faster cure via heat accelera- tion. "We're researching more sophisticated application technolo- gies," he adds, "such as bead injection into cavities for bonding composites to metal frames, and new encapsulated formulations for spot curing under heat acceleration." Another BMW adhesives supplier, L&L; Products (Romeo, MI, US), which entered the automotive/commercial vehicles market with noise, vibration and harshness (NVH) products, already has a composite-to-metal adhesive in serial production. A custom formulated, heat-activated, toughened epoxy flm adhesive is used to bond a carbon/epoxy composite structural stifener to the inside of the BMW 7-Series steel B-pillar. "Te adhesive cure can be as high as 190°C for a sub-1-minute cure time," explains Didier Trau, project manager of advanced development at L&L;'s Molsheim, France, facility. "However, for the BMW process, cure is tailored to match the cure profle of the carbon prepreg, and still achieves a 2-minute cure." Te flm is cut to shape, preformed with the carbon prepreg and cures in the compression molding process that shapes the stifener (see photo, p. 31). Trau notes that no surface preparation is required for either the metal or the prepreg material, saving considerable time. Te flm's elongation accommodates diferences in thermal expan- sion between the composite and the steel. A key point, adds Trau, is that the flm includes an embedded glass veil that ensures consistent separation between the carbon prepreg and the steel substrate, to avoid galvanic efects: "If we used microspheres for bondline control, there is the chance that stray fbers of carbon might still contact the metal. Te veil ensures a complete separa- tion, yet guarantees the minimum bondline thickness." SciGrip Smarter Adhesive Solutions (an IPS company, Durham, NC, US, and Tyne and Wear, UK) supplies acrylic structural adhe- sives to a number of transportation customers, among them GRP HighTech (Bangkok, Tailand), which uses SciGrip's SG5000 1:1 high-performance methyl methacrylate (MMA) for bonding fber- reinforced acrylonitrile butadiene styrene (ABS) rear spoilers and front skirt parts to a metal substructure for major auto OEM customers, including Toyota (Tokyo, Japan). SG5000 report- edly has excellent adhesion to the ABS parts and the stainless steel supports to which they're bonded because acrylics form strong covalent bonds that provide high tensile strength yet also exhibit high elongation (up to 150%) to adjust to variations in CTE. More importantly, its fast room-temperature cure with little or no surface preparation — MMAs are generally suitable Automation increases application speed New World Doors (Ballymena, Northern Ireland) has reduced its cycle time by 73% for its inner door sash bonding step, and signifcantly increased adhesive application speed through the use of an automated dispensing machine. Scott Bader (Wollaston, Northamptonshire, UK) supplies the adhesive: Crystic Crestabond M1-05 10:1 methyl methacrylate (MMA). Source | Scott Bader Adhering to excellence in yacht racing Ian Burns, performance team manager for ORACLE TEAM USA (San Francisco, CA, US), says his yacht-building team uses PRO-SET epoxy adhesives (Gougeon Bros., Bay City, MI, US) to build high-quality small parts, which are eventually joined to elements of the team's racing vessels. The pre-thickened, two-part structural pastes, based on resins and hardeners that do not require elevated-temperature post-cure, reportedly achieve good adhesion and mechanical properties on a great variety of substrates. Source | ORACLE TEAM USA