Interlaminar Shear and Modulus Testing
Fibre-reinforced composite materials depend on effective bonding between individual layers to achieve their required mechanical performance. While reinforcement fibres can provide high strength and stiffness within the plane of a laminate, the interfaces between layers can be more susceptible to shear-related damage and delamination.
Variations in resin systems, fibre architecture, laminate construction, manufacturing conditions, consolidation and void content can all influence interlaminar performance. Insufficient interlaminar strength can result in delamination, reduced structural integrity and premature component failure.
Interlaminar shear testing provides valuable information about the behaviour of composite laminates under shear-dominated loading. Testing to ISO 19927 and ASTM D2344 can support material selection, composite development, manufacturing optimisation, quality assurance and failure investigation.
What Interlaminar Shear and Modulus Testing Involves
Interlaminar testing evaluates the resistance of fibre-reinforced composite laminates to shear-related deformation and failure between their constituent layers.
ISO 19927 specifies a double beam shear method for determining the interlaminar strength and modulus of fibre-reinforced plastic composites. The method is particularly applicable to glass and carbon fibre-reinforced thermoset composites where an acceptable interlaminar failure can be obtained.
ASTM D2344/D2344M specifies a short-beam test for determining the short-beam strength of high-modulus fibre-reinforced polymer matrix composites. The method uses a relatively short specimen subjected to three-point bending to create a stress state in which interlaminar and resin properties can have a significant influence on failure.
Testing can be performed on composite materials including:
- Carbon fibre-reinforced plastics (CFRP)
- Glass fibre-reinforced plastics (GFRP)
- Thermoset composite laminates
- Unidirectional composites
- Reinforced polymer matrix composites
- Composite panels
- Laminated engineering materials
- Development and production composite materials
Depending on the selected method, testing can provide information including:
- Interlaminar strength
- Interlaminar modulus to ISO 19927
- Short-beam strength to ASTM D2344
- Maximum load
- Load-displacement behaviour
- Delamination behaviour
- Failure mode
- Comparative laminate performance
These results provide valuable information for evaluating composite material systems and understanding the influence of resin selection, reinforcement, laminate construction and manufacturing processes.
Methodology
At Impact Solutions, interlaminar shear and modulus testing is carried out using calibrated mechanical testing equipment and appropriate fixtures in accordance with ISO 19927 or ASTM D2344.
A typical testing programme includes:
- Identification of the appropriate test method according to the composite material and required mechanical property.
- Preparation of representative specimens from the composite laminate.
- Conditioning of specimens where required by the applicable test method.
- Measurement and inspection of specimen dimensions and laminate construction.
- Installation of the specimen within the appropriate double beam shear or short-beam test fixture.
- Application of controlled mechanical loading at the specified test rate.
- Continuous measurement of load and displacement throughout testing.
- Determination of interlaminar strength and modulus to ISO 19927 or short-beam strength to ASTM D2344, as applicable.
- Assessment and recording of delamination and other observed failure modes.
- Comprehensive reporting of test conditions, results and observations.
Testing is performed under carefully controlled laboratory conditions to provide accurate, repeatable and reliable composite mechanical performance data.
Relevant Industry Applications
Interlaminar shear and modulus testing is widely applicable to:
- Aerospace composites
- Automotive components
- Marine structures
- Wind energy materials
- Carbon fibre structures
- Glass fibre structures
- Transportation applications
- High-performance sporting equipment
- Composite structural components
- Composite material development
- Manufacturing process optimisation
- Research and development
- Quality assurance programmes
- Failure investigations
Benefits of Interlaminar Shear and Modulus Testing
- Evaluates the interlaminar performance of composite laminates
- Determines interlaminar strength and modulus using ISO 19927
- Determines short-beam strength using ASTM D2344
- Helps identify susceptibility to delamination
- Enables comparison between different composite material systems
- Assesses the influence of resin systems and laminate construction
- Supports optimisation of composite manufacturing processes
- Provides mechanical performance data for material development
- Supports quality assurance and process specification
- Helps investigate unexpected composite failures
- Uses internationally recognised ISO and ASTM test methods
Need to assess the interlaminar performance of your composite materials?
Contact Impact Solutions to discuss interlaminar shear strength and modulus testing to ISO 19927 and short-beam strength testing to ASTM D2344 and obtain reliable mechanical performance data for your fibre-reinforced composite materials.
FAQ
Q: What is interlaminar shear strength?
Interlaminar shear strength relates to a composite laminate’s resistance to shear-related failure between its individual layers. It is particularly important in fibre-reinforced composites because the through-thickness properties of a laminate can be significantly different from its properties in the fibre direction.
Q: What is interlaminar shear modulus?
Interlaminar shear modulus describes the stiffness of a composite material when subjected to interlaminar shear deformation. ISO 19927 enables both interlaminar strength and modulus to be determined using the double beam shear method.
Q: What materials can be tested?
Testing is particularly applicable to fibre-reinforced polymer composites, including carbon fibre and glass fibre laminates. The appropriate test method depends on the composite construction, reinforcement system and mechanical properties required.
