Continued advancements in the design and manufacture of engineered composites has allowed composite materials to work their way into the products we use everyday. By definition, a composite material is simply any material that contains two or more constituent materials. The materials that make up a composite are chosen either to enhance or supplement the material properties of the individual materials. The typical material combination seen in today's composites is a material that performs well in tension (fiber or rebar) paired with a material that performs well in compression (epoxy, ceramic, or cement). The most common modern advanced composites are fiber-matrix composites and they can be manufactured with polymer, carbon, metal, or ceramic matrix and an extremely wide range of reinforcement fiber including, carbon, graphite, boron, aramid, and glass. Most engineering materials are not used in practice in the form they are tested. This is no different with composite materials, as a functional composite part is likely to have cutouts, holes, screws, rivets, or irregular shape. Open-hole tests of composites help to address the real life application of composite materials. The presence of an open hole in a composite component reduces the cross-section area available to carry an applied load, creates stress concentrations, and creates new edges where delamination can occur. Performing standardized open-hole tests for composite materials can provide useful information about how a composite may perform in an open-hole application. However, due to the nature of composites, it is often necessary to also conduct full scale component tests for products, such as airplane fuselages, where holes and irregular geometries are unavoidable.

ASTM has developed standard test methods for testing the open-hole strength of composites. The standards provide methods that can be recreated, ensuring materials are tested in the same manner and conditions and allowing test results validation between manufactures and customers. Popular test methods are ASTM D5766 for open-hole tensile strength of polymer matrix composites, ASTM 6484 for open-hole compressive strength of polymer matrix composites, and ASTM D7615 for open-hole fatigue of polymer matrix composite laminates. Open holes do reduce the tensile and compressive strength of a composite test specimen, but even this reduced strength can be very large. The required machine force capacity necessary to conduct open-hole composites tests varies depending on the test specimen material and geometry. The machine families below can be matched to the wide range of composite materials being tested. The unique properties of composites require that many grips and fixtures be custom made. The grips below are designed to meet ASTM D5766 and ASTM D6484 test requirements and TestResources can manufacture grips to meet your unique fixturing requirements. Contact a TestResources application engineer to determine the best machine and grip combination for your exact testing needs.

Applicable Testing Standards

Recommended Testing Accessories