EN 2563 Unidirectional Laminates - Determination of Apparent Interlaminar Shear Strength

A European standard “EN 2563 Aerospace series - Carbon fibre reinforced plastics - Unidirectional laminates - Determination of apparent interlaminar shear strength” describes a method for determining the apparent interlaminar shear strength of carbon fibre reinforced plastics in the form of unidirectional laminates by means of bending testing.

This method is designed for samples where the length is parallel to the fiber direction. The method is also applicable to carbon fiber-reinforced plastics in the form of woven fabrics. In the case of cross-ply laminates consisting of layers oriented in different directions, the results obtained with the formula given in this standard can only be used to compare laminates with the same layering.

For the purposes of this standard, apparent interlaminar shear strength refers to the maximum shear stress calculated at half the thickness of the specimen at the moment of initial fracture.

This method essentially involves determining the resistance to delamination under shear forces parallel to the laminate layers. For this determination, a rectangular specimen is subjected to a bending test on two supports. The load is applied to the center of the specimen via a loading nose located between the supports. This test provides information about the quality of the resin-fiber bond.

Samples for tests are taken from panels prepared according to EN 2655 standard.

Conditioning is carried out in accordance with the following conditions:

According to EN 2743 standard for initial state tests
According to EN 2489 standard for post-immersion tests
According to EN 2823 standard for tests after exposure to a humid atmosphere

During the test, the width is measured to the nearest 0,01 mm at the center of the specimen. The height is determined by calculating the arithmetic average of three thickness measurements taken at the center of the specimen along the width to the nearest 0,01 mm. The distance between supports is measured to the nearest 0,1 mm.

For qualification testing and in case of dispute, the distance between supports should be adjusted according to the formula given in the standard:

For tests performed at temperatures other than ambient, the time between conditioning and the start of the test must meet the following conditions:

For samples that have not been aged or immersed, the exposure time at the test temperature should be determined by preliminary tests.
For samples subjected to immersion, the EN 2489 standard applies.
For samples subjected to a humid atmosphere, the EN 2823 standard applies.

The specimen is placed in the test fixture, ensuring its axis is perpendicular to the supports. The specimen is loaded uniformly. The load is recorded as a function of time or displacement of the loading nose. The load at fracture is recorded.

If a specimen fractures in shear approximately along the neutral fiber axis, the interlaminar shear strength is calculated using the formula given in this standard. If a specimen fractures in bending or plastic deformation, the result obtained using the formula given in this standard is not the true shear stress at fracture. This result can only be used for comparison with results from a series of tests on the same subject.

The EN 2563 standard is a European standard that specifies the method for determining the apparent interlaminar shear strength of fibre-reinforced plastic composites using the short-beam method.

This standard provides a standard test procedure for:

Evaluating the interlaminar shear properties of composite materials

Ensuring consistency and comparability of test results across different laboratories and industries
Assisting in material selection, quality control and design verification of composite structures

Interlaminar shear strength represents a material's ability to resist shear between layers (laminas). It is particularly critical in layered materials such as carbon fiber or glass fiber composites, where delamination can be a significant failure mode.

This standard is deemed necessary for the following reasons:

Design assurance: Helps engineers ensure that composites used in aerospace, automotive, marine and construction applications can withstand shear loads without delamination.
Quality control: Manufacturers use the EN 2563 standard method to verify that their composite parts meet performance specifications.
Standardization: Without a standard such as EN 2563, different testing methods may yield incomparable results, making it difficult to reliably assess material quality or performance.
Regulatory compliance: Many industries require materials to meet certain standards before they can be used in safety-critical applications.

Carbon fiber-reinforced plastics are composite materials made from a polymer matrix, usually epoxy, reinforced with carbon fibers. The carbon fibers provide exceptional strength and stiffness, while the polymer matrix bonds the fibers and distributes the loads. This combination results in a lightweight, strong, and durable material, making it ideal for high-performance applications.

The main properties of carbon fiber reinforced plastics are:

High strength-to-weight ratio: Stronger than steel but much lighter, ideal for weight-sensitive applications.
Hardness: High modulus of elasticity resists deformation under load.
Corrosion resistance: Unlike metals, carbon fiber reinforced plastics do not corrode, increasing durability in harsh environments.
Fatigue resistance: Excellent performance under cyclic loading makes them suitable for dynamic applications.
Thermal stability: Low thermal expansion and good performance over a wide temperature range.
Design flexibility: Can be molded into complex shapes, allowing for custom structural designs.

Unidirectional laminates are composite materials in which all reinforcing fibers are aligned in a single direction within a matrix, typically a polymer such as epoxy. This alignment gives the laminate high strength and stiffness along the fiber direction, but much lower properties perpendicular to it. They are used in applications such as aerospace, automotive, or sporting goods where specific directional strength is required, such as beams or structural components. The fibers, typically carbon or glass, are embedded in the matrix to hold them together and transfer loads.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, boasts a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the EN 2563 Aerospace series - Carbon fiber-reinforced plastics - Unidirectional laminates - Determination of apparent interlayer shear strength standard.