Composite Laminates Tensile Testing

THE CHALLENGE

The successful use of composite materials demands a thorough understanding of their mechanical properties throughout their operating temperature range. The anisotropic and heterogeneous nature of composite materials means that a range of different mechanical tests, many requiring special fixtures, are required for full characterisation. Maintaining accurate mechanical alignment and minimizing set-up times when switching between test types is a major challenge for laboratories testing composite materials.

OUR SOLUTION

An integrated testing system consisting of accurately aligned precision grips along with a comprehensive range of test fixtures that can be mounted onto the grips provides an effective and productive solution for composites laminates testing. An optional temperature chamber provides the ability to test over a wide temperature range. In addition, the Composites Application Module for Bluehill^® Universal software provides a range of, easy-to-use test methods for international standards (e.g. ASTM, EN, and ISO).

The Challenge

Maintaining high test productivity along with consistent tensile test results is a challenge. High test productivity, particularly when testing at temperatures, demands that the operator spends as little time as possible loading specimens. Achieving the accurate specimen alignment needed to produce consistent results is difficult given these time constraints.

Traditionally, strain measurements on composite materials have been made using bonded strain gauges but the bonding of strain gauges is a costly and time-consuming process that requires a high degree of skill and experience. Thus, the strain gauging process reduces overall productivity and increases test costs.

Precise specimen alignment requires an accurately aligned testing set-up and repeatable grips incorporating a reliable means of specimen location.

Both manual and automatic (hydraulic) gripping solutions capable of providing quick specimen loading and accurate alignment are available. These grips can be used in an environmental chamber to test over a range of temperatures.

Extensometers are available for the testing of composite laminate coupons and, in most cases, they can be used to replace strain gauges.  Averaging Axial and Biaxial types provide both average axial and transverse strain measurements (for the determination of Poisson’s ratio).

In cases where bonded strain gauges must be used strain gauge adapters can be used to connect strain gauges directly to the test machine. In addition to contacting solutions, the Advanced Video Extensometer (AVE2) non-contacting video extensometer offers completely automatic operation requiring minimal action from the operator.

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