Overview: The Seeman Composites Resin Infusion Molding Process (SCRIMP) is a vacuum-assisted resin transfer molding process that produces parts excellent for marine, aerospace, transportation, and infrastructure applications. The process is a proven method of producing high-quality composite parts made from a wide range of fiber and resin combinations. All commercial fibers, core materials, and any resin in the range of 50 centipoise to 1000 centipoise will “SCRIMP” with outstanding results. The process can be run at room or elevated temperatures. SCRIMP can produce large (2,000 sq. ft.) parts, using both single skin and cored construction, and highly complex three-dimensional trussed parts weighing up to 3,000 lbs. The resulting composite material properties directly compare to properties that had only been achievable in highly controlled expensive autoclave processes.
The SCRIMP process is inherently repeatable. Once equilibrium resin content is achieved (55% to 60% fiber volume, depending on fabric architecture), the process stops. Aerospace grade quality is ensured by first eliminating all air voids before the resin is infused, enabling the fabric pre-form to act as an effective breather layer. As the resin is infused, it travels in controlled waves that work to completely wet out the reinforcing fibers and eliminate any voids that could be created by the volatile organic compounds (VOCs) emitted by the resin during the cure cycle. The process has been used to infuse laminates up to 6 inches thick with the same high-quality results as a simple 1/8 inch laminate. The Navy has extensively tested SCRIMP laminates and has concluded that the void content can not be detected with standard ASTM methods. With or without a gel coat, composites produced using SCRIMP exhibit pinhole-free surfaces.
The Navy has developed prototypes of varying structures, such as ship’s masts, Navy Seal submarines, and sensor systems. The SCRIMP process also is being used to make sailboats, railcar bodies, intermodal shipping containers, bridge decks, windmill blades, and pilings, among other applications.
One example of the application of the SCRIMP process is the Hardshaft manufacturing process. The process is used to manufacture marine construction products, such as fiberglass tubular pilings and marine fender panels. The process has extreme versatility and can produce pilings of any size up to 300 feet long and six feet in diameter. Benefits specific to the Hardshaft application are:
Does not rot or corrode as some conventional materials do.
Does not leach chemicals into water bodies.
Custom engineered for each job; manufactured in any length, diameter, or thickness.
Impervious to marine borers.
Installed using conventional equipment.
Compliance Benefit: Due to significant reductions in emissions of VOCs and other air pollutants, the SCRIMP closed system may decrease the need for an air permit under 40 CFR 70 and 40 CFR 71. In addition, smaller amounts of hazardous materials (i.e., solvent) are required for the SCRIMP system. As a result, the possibility that the facility would meet any of the reporting thresholds of SARA Title III (40 CFR 300, 355, 370, and 372) is decreased.
The compliance benefits listed here are only meant to be used as general guidelines and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g., the amount of workload involved.
Materials Compatibility: No materials compatibility issues were identified.
Safety and Health: The SCRIMP process increases worker safety by reducing VOC emissions. Consult your local industrial health specialist, your local health and safety personnel, and the appropriate MSDS prior to implementing this technology.
Benefits: Closed system traps VOC emissions.
Minimal need for solvents reduces VOC emissions by as much as 90% over open molding processes.
Styrene levels are decreased, eliminating the need for the exchange of heated air.
Reduces the need for masks, gloves, and protective clothing.
Improved product quality.
Reduced labor and materials needs.
Disadvantages: The SCRIMP process is patented and expensive to license.
Licensees must pay a royalty on all products manufactured using the SCRIMP process.
Economic Analysis: The SCRIMP process is a patented system licensed for $25,000. Hand layup, the conventional method of marine construction, is a labor-intensive process resulting in a product with relatively high porosity and low fiber content that reduces strength and stiffness. The unit cost per pound of labor and materials for a generalized structural configuration, based on an assumption of $40/hour shipyard labor, is less than $10/lb. The SCRIMP process may decline in price in the future, as it is currently being used for producing prototypes in many applications. The SCRIMP process, currently at a comparable cost, produces a higher quality product while emitting fewer VOCs, which can endanger workers. Currently, the cost of using the SCRIMP process is less than $10/lb.
Based on the construction of four, one-half scale midship sections of a medium-sized 280-ft., 1200-ton naval combatant, the SCRIMP process produced a hull section weighing slightly under 23,000 pounds, including 13,000 pounds of glass and 7,000 pounds of resin. The production time for fabricating the hull section was 3,154 labor hours.
Another example of an application that has been used more widely is pilings. The following assumptions were used to compare the cost of Hardcore pilings using the SCRIMP process to conventional CCA pilings:
Assumptions:
Cost of a Copper/Chromium/Arsenate (CCA) piling is $4/ft.
Cost of a Hardcore Fiberglass Tubular Piling is $15/ft.
Lifespan of a CCA piling is 10 years.
Lifespan of a Hardcore piling is 30 years.
Cost to install a piling is $50/hr.
Time required to install a 40 foot piling is 8 hours.
CCA Pilings Hardcore Pilings
Capital Costs for a 40 ft. piling: $160 $600
Installation Costs over 30 years: $1200 $400
Total Costs: $1360 $1,000
Although the Hardcore pilings cost more initially than conventional pilings, the costs involved in replacing the shorter-lifespan, conventional pilings increase the overall costs of conventional pilings significantly. In the longterm, Hardcore pilings are more cost effective.
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NSN/MSDS: None identified.
Approving Authority: Appropriate authority for making process changes should always be sought and obtained prior to procuring or implementing any of the technology identified herein.
Points of Contact: For more information
Vendors: This is not meant to be a complete list, as there may be other suppliers of this type of equipment.
TPI Composites, Inc.
P.O. Box 328
Warren, RI 02885
Phone: (401) 245-1200
FAX: (401) 247-2669
Sources: Research Release "Low Cost, High Quality composite Ship Structures Technology Demonstrated," Headquarters, David Taylor Model Basin, Naval Surface Warfare Center, Carderock Division, Bethesda, MD, May 1993.
Nguyen, Loc D., Thomas Juska, and J. Steven Mayes, "Evaluation of Low Cost Manufacturing Technologies for Large Scale Composite Ship Structures," Naval Surface Warfare Center, Carderock Division, West Bethesda, MD, Presented to 38th Structures, Structural Dynamics, and Materials Conference and Exhibit, AIAA/ASME/AHS Adaptive Structures Forum, Kissimmee, FL, April 7-10, 1997.