Individual Parts Bring a Greater Whole

A primer on MCMs
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Sponsored by Metal Construction Association
By Amanda C Voss, MPP

Learning Objectives:

  1. Explain what a metal composite material (MCM) is and how it is produced.
  2. Review the available options for MCM skins, including finishes, materials, and specifications, and how these aesthetic options can elevate occupant experience.
  3. Discuss how MCM skins promote sustainability and practicability of the structure through its life cycle, shielding it from everyday wear and leading to enhanced building durability and health.
  4. Describe the attributes of MCM core material and how these benefit occupants and create a safer structure during fires.
  5. Debate the benefits MCM provides, including those related to environmental concerns, efficiency, and economy. Demonstrate how MCM, as a designed material bolsters structural lifespan, green goals, and the well-being of users.

Credits:

1 AIA LU/HSW
1 AIBD P-CE
0.1 IACET CEU*
AAA 1 Structured Learning Hour
AANB 1 Hour of Core Learning
AAPEI 1 Structured Learning Hour
SAA 1 Hour of Core Learning
MAA 1 Structured Learning Hour
NSAA 1 Hour of Core Learning
OAA 1 Learning Hour
NLAA 1 Hour of Core Learning
NWTAA 1 Structured Learning Hour
 
This course can be self-reported to the AIBC, as per their CE Guidelines.
This course is approved as a Structured Course
Approved for structured learning
This course is approved as a core course
Approved for Core Learning
Course eligible for OAA Learning Hours
This course is approved as a Core Course
Course may qualify for Learning Hours with NWTAA
This course can be self-reported for Learning Units to the Architectural Institute of British Columbia

Clustered around a plan table, a group of architects in Vancouver, British Columbia, face a daunting task. The team needs a wall assembly that can actually realize the bends, rolls, and shapes they have created with their 3-D design software. This wall assembly must support the building’s environment and primary use. It has to enable the design to exceed LEED New Construction Platinum standards. It must withstand the rain and humidity that are a reality in Vancouver. Finally, it will support and integrate with a living, fully vegetated rooftop.

Photo courtesy of Metal Construction Association

FECHAC REGIONAL OFFICES, CIUDAD JUAREZ, MEXICO
Metal composite material (MCM) meets the challenges faced by today’s architects and design professionals.

Challenge accepted. In the end, one material is the team’s natural choice for the wall assembly on this project: metal composite material.

Metal Composite Material

Metal composite material, or MCM, is formed by joining two metal skins to a solid plastic or fire-retardant core, which is then bonded under a precise temperature, pressure, and tension. This unique process makes MCM lighter, more versatile, and more flexible than a solid metal of similar thickness.

MCM has transformed modern architecture. Building owners and architects wanting to make a design statement can look to the current generation of MCM for a wide range of interior and exterior options. The smooth, sleek material can be bent, curved, and joined in various shapes and configurations, and the panels keep their luster for years with minimal maintenance. MCM turns buildings into timeless works of art.

Where It Came From: Product History

The first aluminum composite material (ACM) was created as a result of a newly patented process of bonding aluminum to polyethylene for the communication industry. Alusuisse Aluminum then created the first ACM for use in the construction industry in 1969. It was not until 1979 that the first ACM was produced in North America. In the early 1980s, there were only a few companies worldwide producing ACM and shipping materials to North America for architectural projects.

During the 1990s, three companies were manufacturing ACM in North America, competing with foreign imports. Processes were developed to use alternate skin materials, such as copper, zinc, steel, stainless steel, and even titanium. With this skin material change, the product category was broadened to MCM.

Today, the number of manufacturers continues to grow worldwide, and the amount of variation in product offering and level of available product quality continues to expand along with it. Aluminum skins, alternate metal skins, solid plastic core, metal honeycomb core, metal corrugated core, honeycomb plastic core—the list of products that identify as composite materials components is almost endless. The one constant that remains is that MCM cannot contain foam plastic material.

Photo courtesy of Arconic Architectural Products

CHARLESTON COLISEUM AND CONVENTION CENTER, CHARLESTON, WEST VIRGINIA
The unique production process used to create MCM makes it lighter, versatile, and more flexible than a solid metal of similar thickness.

How It Is Made: Production of MCMs

One of the most significant variables seen within MCMs is the production process.

That said, the production process is fairly straightforward. Typically, an extruded core material is produced, followed by the application of a selected material that will bond the elements together. Finally, a metal skin material is added to provide both structural stability and a medium that can be finished in a number of colors and finish types. The individual elements are organized and passed through a bonding process. This process provides significant heat, pressure, and tension in order to bond the individual elements together, creating the MCM. It takes the combination of all three elements—heat, pressure, and tension—to create a complete composite panel. One of the most critical elements in the production of MCM is the bond strength between the core and the metal skin material. This bond is developed using a very precise chemistry, which bonds the metal and the traditionally bond-resistant core material, usually a polyethylene-based compound. To ensure the bond strength is within acceptable levels, manufacturers are required to test the bond strength, as manufactured, after 8 hours in boiling water, and after 21 days soaking in water at room temperature. These standard tests have worked well in the past and are required as part of the product-evaluation process to assure the panel will remain intact over time. Based on many thousands of square meters of experience, it was determined that a bond strength, both as manufactured and after controlled exposure, of 22.5 inch-pounds/inch (measuring bond peeling strength) was adequate to ensure that a panel remains a composite during normal exterior applications. This performance value has been built into the requirements used by all major manufacturers and certification agencies to evaluate the acceptability of the finished MCM.

After bonding, the panel must be cooled in a controlled process to maintain both the bond integrity and surface flatness. Because the metal skin is expanded at the higher bonding temperature, the skin contracts as it cools, making the entire assembly want to move, twist, and bow until the finished panel reaches ambient temperature. Without the controlled use of heat, pressure and tension, the panel will not achieve the signature uniformity of the MCM product. Overall flatness is also a major concern for an exterior cladding to maintain the desired absolutely flat appearance. Furthermore, the bond strength and panel flatness are the attributes that will make the panel perform against the elements and be visually acceptable, even after years of exposure.

Changes in the production process and material choices by newer companies joining the MCM manufacturer contingent are a significant consideration when defining the quality of the MCM in recent years. Various manufactures have created composite panels using a batch process; however, consistent visual appearance and bond strength between elements has not generally met the quality and consistency experienced in the continuous lamination process. Continuous panel production in a controlled factory environment has proven to be the most common best practice to ensure a high-quality, consistent panel product.

Codes

Chapter 2 of the International Building Code (IBC) defines an MCM as “a factory-manufactured panel consisting of metal skins bonded to both faces of a solid plastic core.”

The IBC contains a specific section dedicated to the use of MCM in construction: Section 1406. Section 1406 contains considerable detail about physical and fire performance, including the required testing to allow the use of MCM on practically all types of construction.

The building code has always looked at foam plastic and foam-plastic-containing materials as a different kind of product than MCM due to concerns of fire. These products and assemblies containing foam plastic are regulated in Chapter 26 of the code.

 

[ Page 1 of 5 ]       
Originally published in Architectural Record

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