Published 01/14/2026

From PMCs to sandwich composites: Tracing the path of test method standardization

Over the decades, progression of PMC and sandwich composite test method development and standardization has been shaped by the requirements of the composites industry.

Design and Testing

Dan Adams

President, Wyoming Test Fixtures Inc.

One of the recurring themes in this column over the past few years has been the development of new test methods for sandwich composites. This is primarily a result of the opportunities I’ve had to participate in the development and ASTM standardization of these test methods, and this CW column has been an excellent forum for providing updates to the broader composites community.

In recent years, there’s been a steady stream of newly standardized test methods for sandwich composites, while the pace of newly standardized test methods for conventional polymer matrix composites (PMCs) has slowed considerably. In large part, this difference in standardization reflects where these two types of composites currently stand along the natural progression of test method development. As applications for these composite materials mature, the need for additional material properties becomes apparent, and the corresponding test methods are developed and standardized to meet these needs.Whereas PMCs have largely completed this progression, sandwich composites are still in the midst of it.

The following discussion focuses on the ongoing progression of test method standardization for sandwich composites. It highlights their similarities and differences in progression in contrast to conventional PMCs, and how test method development for each have diverged over the decades

The availability of E-glass in the 1950s and carbon fiber in the 1960s led to the development of PMCs. Formal ASTM standardization of test methods began in the 1960s. Early test method development efforts focused on determining stiffness and strength properties under tension, compression and shear loadings. However, increases in the stiffness and strength properties of carbon fiber during the 1960s created significant testing challenges — and were the driving force behind the creation of several new test methods for PMCs in the 1970s. The 1980s brought some stability as carbon fiber/epoxy composites matured, and initiated a second period of test method development to address newly introduced toughened epoxies and thermoplastics, as well as high-temperature bismaleimide and polyimide resins. New test methods were required to assess their damage tolerance, leading to the development of open‑hole tension and compression test methods, and later to compression‑after‑impact test methods. By the mid-2000s, the ASTM standardized test methods for PMCs had reached a mature phase. A summary of this timeline of test method development for PMCs is shown in the left column of Table 1.

Table 1. Comparison of timelines for ASTM test method standardization: PMCs versus sandwich composite test methods.

The development of standardized test methods for sandwich composites has followed a similar path, but over an extended timeline that ranged from the early 1950s to the present. As summarized in the right column of Table 1, the earliest standardized tests for sandwich composites emerged in the early to mid-1950s, when honeycomb cores and thin facesheet constructions were first used in aerospace applications.

The initial test methods for core shear testing (ASTM C273¹), flatwise tension testing (ASTM C297²), and edgewise compression testing (ASTM C364³) were used to address the relatively narrow range of material property requirements at the time. However, as sandwich composites expanded into more demanding aerospace and marine applications, new material property requirements emerged. These requirements led to the development of additional test methods to address facesheet-to-core bond integrity (ASTM C363⁴) and core shear strength by beam flexure (ASTM C393⁵).

Unlike the test method development for PMCs — which reached maturity in the early 2000s — sandwich composite test method development entered a second period of activity beginning around the same time. Between 2000 and 2020, a total of seven new test methods were introduced, including a 2D flexural test for sandwich composite plates (ASTM D6416⁶), long beam flexure tests for strength (ASTM D7249⁷) and stiffness (ASTM D7250⁸), and a picture frame shear test (ASTM D8067^9-10). These test methods expanded the material property set beyond the foundational core‑dominated tests and reflected the growing structural demands placed on sandwich constructions.

Since 2020, five additional sandwich composite test methods have been standardized by ASTM, all of which have been featured in my CW columns. In 2022, four new sandwich composite test methods were standardized. Two addressed damage tolerance — compression-after-impact (ASTM D8287¹⁰) and flexure-after-impact tests (ASTM D8388¹¹) — and two addressed notch sensitivity — open-hole flexure (ASTM D8453¹²) and open-hole compression (ASTM D8454¹³). In 2025, the first fracture mechanics test method for sandwich composites, the Mode I single cantilever beam test (ASTM D8637¹⁴), was standardized, which was the subject of my May 2020 CW column as well as my most recent November 2025 CW column.

In summary, the history of test method development and standardization for both PMCs and sandwich composites shows that standardization has followed a natural progression driven by application maturity. PMCs moved through this progression earlier, reaching a stable and largely complete suite of standards by the early 2000s. Sandwich composites, by contrast, are still advancing, with new applications driving the creation of additional test methods.

References

¹ASTM C273/C273M-20, “Standard Test Method for Shear Properties of Sandwich Core Materials,” ASTM International (W. Conshohocken, PA, US), 2020 (first issued in 1951).

²ASTM C297/C297M-16 (2024), “Standard Test Method for Flatwise Tensile Strength of Sandwich Constructions,” ASTM International (W. Conshohocken, PA, US), 2024 (first issued in 1952).

³ASTM C364/C364M-16 (2024), “Standard Test Method for Edgewise Compressive Strength of Sandwich Constructions,” ASTM International (W. Conshohocken, PA, US), 2024 (first issued in 1955).

⁴ASTM C363/C363M-24, “Standard Test Method for Node Tensile Strength of Honeycomb Core Materials,” ASTM International (W. Conshohocken, PA, US), 2024 (first issued in 1955).

⁵ASTM C393/C393M-20, “Standard Test Method for Core Shear Properties of Sandwich Constructions by Beam Flexure,” ASTM International (W. Conshohocken, PA, US), 2020 (first issued in 1960).

⁶ASTM D6416/D6416M-16 (2024), “Standard Test Method for Two-Dimensional Flexural Properties of Simply Supported Sandwich Composite Plates Subjected to a Distributed Load,” ASTM International (W. Conshohocken, PA, US), 2024 (first issued in 2001).

⁷ASTM D7249/D7249M-20, “Standard Test Method for Facesheet Properties of Sandwich Constructions by Long Beam Flexure,” ASTM International (W. Conshohocken, PA, US), 2020 (first issued in 2006).

⁸ASTM D7250/D7250M-20, “Standard Practice for Determining Sandwich Beam Flexural and Shear Stiffness,” ASTM International (W. Conshohocken, PA, US), 2020 (first issued in 2006).

⁹ASTM D8067/ASTM D8067M-17 (2025), “Standard Test Method for In-Plane Shear Properties of Sandwich Panels Using a Picture Frame Fixture,” ASTM International (W. Conshohocken, PA, US), 2025 (first issued in 2017).

¹⁰ASTM D8287/ASTM D8287M-22, ”Standard Test Method for Compressive Residual Strength Properties of Damaged Sandwich Composite Panels,” ASTM International (W. Conshohocken, PA, US), 2022.

¹¹ASTM D8388/ASTM D8388M-22, ”Standard Practice for Flexural Residual Strength Testing of Damaged Sandwich Constructions,” ASTM International (W. Conshohocken, PA, US), 2022.

¹²ASTM D8453/ASTM D8453M-22, “Standard Practice for Open-Hole Flexural Strength of Sandwich Constructions,” ASTM International (W. Conshohocken, PA, US), 2022.

¹³ASTM D8454/D8454M-22, “Standard Test Method for Open-Hole Compressive Strength of Sandwich Constructions,” ASTM International (W. Conshohocken, PA, US), 2022.

¹⁴ASTM D8637/D8637M-25, “Standard Test Method for Mode I Dominant Face Sheet-to-Core Fracture Toughness of Sandwich Constructions,” ASTM International (W. Conshohocken, PA, US), 2025.