Flat Crush Test (FCT)

The flat crush test (FCT) is a recognised method for measuring the resistance of corrugated fibreboard to a compressive load applied perpendicularly to its surface. This test assesses the strength of the board’s fluting, which is critical for protecting goods during handling, storage, and transportation.

By determining the board’s ability to withstand compression, the FCT ensures packaging maintains its structural integrity under real-world conditions. This is particularly important in e-commerce, food distribution, and retail sectors, where packaging must resist stacking loads, mechanical stresses, and environmental impacts.

The compressive resistance of corrugated cardboard depends on factors such as flute profile, board structure, and paper quality. These directly affect performance under flat crush loading.

The role of flute material

Fluting is the arched paper layer between the linerboards in corrugated fibreboard. Different flute types have distinct performance characteristics:

• A-flute: High stacking strength and cushioning properties, with lower crush resistance than finer flutes.
• B-flute: Greater puncture resistance and crush strength, often used in retail packaging.
• C-flute: Balanced stacking and crush resistance, widely used in shipping cartons.
• E- and F-flutes: Fine flutes for lightweight packaging and printing applications, with high crush resistance in a compact form.

Selecting the correct flute type helps ensure the board meets the performance requirements of the intended application.

FCT results must be consistent and comparable, which is why the test is carried out to recognised standards:

• FEFCO: European test methods for corrugated board, including FCT.
• ISO 3035: Method for determining the flat crush resistance of corrugated fibreboard.
• TAPPI T 808: Widely used in North America for measuring FCT.

These standards define specimen preparation, load application speed, and conditioning requirements to produce repeatable results.

The flat crush test measures the compressive strength of the fluted structure in finished board, taking into account liners and adhesives. The Concora medium test (CMT) measures the crush resistance of the fluting medium before it is formed into board.

• FCT is suited for assessing finished board performance.
• CMT is used for evaluating raw flute material.

The choice of test depends on whether the aim is to control raw material quality or validate the final product.

A standard flat crush test includes the following stages:

• Sample preparation - Specimens are cut to size, with clean edges and representative flute orientation, and conditioned for stable moisture content.
• Equipment setup - The sample is placed between two parallel compression plates to ensure uniform loading.
• Test execution - A compressive load is applied at a constant speed as specified in the relevant standard.
• Data measurement - The peak load at which the flutes collapse is recorded as the flat crush resistance.
• Result interpretation - Values are compared against specification limits or historical data to confirm compliance.

Typical single-wall corrugated boards may show flat crush values in the range of 2.5 to 4.5 kN/m, although this depends on flute type, board grade, and environmental conditions.

FCT is an essential quality control and design optimisation tool for:

• E-commerce: Ensuring cartons retain strength when stacked during transport.
• Food packaging: Preventing deformation during chilled or ambient storage.
• Retail: Maintaining product presentation and safety on shelves.

Key benefits:

• Reduces the risk of packaging failure.
• Enables cost-effective material selection.
• Improves product safety during transport and storage.

Mecmesin provides precision-engineered flat crush testing solutions designed for accuracy, repeatability, and compliance with ISO, TAPPI, and FEFCO standards.

Standards-ready fixtures

Our test stands, including the OmniTest and MultiTest-dV ranges, can be configured with fixtures such as PDV11089 pelleting plates for uniform load distribution and PSV21062 precision guide fixtures for accurate specimen alignment.

Customisable systems

Using VectorPro software, operators can control test parameters, capture peak load values, and generate detailed reports for quality control or customer compliance records. Systems are adaptable for different board grades and flute profiles, ensuring testing matches specific production needs.

If you need to implement flat crush testing for corrugated fibreboard in line with international standards, Mecmesin can provide the right equipment, fixtures, and expertise. Our technical team can help you select the best configuration for your materials, ensuring accurate, repeatable results that improve packaging performance and reliability.