Standards Development

Scope

The proposed standard defines the general principles for determining stress-strain curves for plastics in a wide strain rate field, with a focus on data entry of material cards for finite element simulations in the event of transient loads (impact/crash). The procedure is to be used to investigate the strain rate dependent uniaxial tensile deformation behaviour of test specimens and to determine the tensile stress-strain relationship under noncyclic, highly dynamic conditions. The procedure is particularly suitable for use in the material group of injection-moulded thermoplastics, unfilled and filled, including short fiber reinforced thermoplastics with a fiber length of up to 7.5mm as well as curable plastics. The proposed standard only describes tests in a standard climate.

Purpose

The proposed standard shall define the general principles for determining stress-strain curves for injection-moulded thermoplastics, unfilled and filled, including short fiber reinforced thermoplastics with a fiber length of up to 7.5mm as well as curable plastics, with a focus on the data entry of material cards for finite element simulations in the event of transient loads (impact/crash). Computer Aided Engineering (CAE) is deeply rooted in product development. Without the application of CAE various requirements like time, costs, performance, resource conservation, etc. cannot be achieved.

Dynamic structural simulation of plastics is state of the art within the automotive industry (crash) as well as the electrical & electronic industry, household appliances (drop / fall). Standard material models for dynamic plastic simulation require the same test data, which is uniaxial tension data at different loading speeds / strain rates. This requirement is independent on the applied software, like Abaqus Explicit, LS-DYNA, Radioss or PAM-CRASH.

Although "standard simulations" of plastics require the same input there is no recognized industry standard for determining the needed data, neither nationally nor internationally. ISO 18872: Plastics - Determination of tensile properties at high strain rates is unsuitable due to the specimen shape and too low speeds. SAE J2749: High Strain Rate Tensile Testing of Polymers is not detailed enough and only gives general comments. In addition, it is currently in draft status.

Therefore, each OEM, TIER, material supplier or test institute has its own requirements / specifications. The negative impacts for OEMs and TIERs are manifold. Material data is not available in the required quality, material data is not available at the start of the project, comparability of materials is difficult and even impossible. For material suppliers there are also diverse issues. Material suppliers are confronted with a variety of requirements and in some cases, materials need to be tested in several configurations to satisfy different customers.

Therefore, an international standard which would specify the general principle for determining stressstrain curves for injection-moulded thermoplastics, unfilled and filled, including short fiber reinforced thermoplastics with a fiber length of up to 7.5mm as well as curable plastics, with a focus on the data entry of material cards for finite element simulations in the event of transient loads (impact/crash) would, amongst others, significantly reduce costs, resources, and time.

There is a verified marked need for the proposal which can be document identified with the project members, which started the first analysis. Following markets would be positively affected: Automotive OEMs, Tier1, Tier2, E&E, material suppliers, test institutes, software companies, etc