Flexure Testing of Plastics

ISO 178, ASTM D790

ISO 178, ASTM D790

ISO 178 and ASTM D790 norms deal with the determination of the flexural properties of the unreinforced plastics

Among the most commonly used in the sector, they allow the determination of the maximum stress, flexural modulus and others related to a particular state of stress.  The fixture allows a 3-point bending, where shape and distance of the anvils are in compliance with Standards. 

Test consists in positioning the specimen on a crosshead with two points of support and gives a deflection on a punch which presses on the centerline of the specimen, thus generating a bending of the specimen itself. The use of an additional reading device of the maximum deflection in the central point is always recommended if the elastic modulus has to be calculated.

Tested materials: thermoplastic dies and extrusion materials, including reinforced and loaded compounds, in addition to the not loaded types, thermoplastic rigid sheets, thermosetting materials for dies, including reinforced and loaded compounds, thermosetting sheets. For reinforced materials it is advisable to evaluate other types of standards such as ISO 14125 and ASTM D6272.

Both 3 and 4-point flexural loading devices are used to evaluate plastics. The loading and the dimensions of the anvil support can differ from the specimen thickness. We use the software Labtest preload characteristic to determine the loading start, at this point, the strain measurement devices can automatically re-balance. The load supported by the specimen is measured during this procedure.

Flexural devices are designed to be mounted on benchtop or floor standing Quasar machines equipped with software Labtest where specimen data, automatic control of the test according to Standard parameters, automatic calculation of the results and statistical analyses for the tested material qualification will be entered.

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Le Norme ISO 178 e ASTM D790 si riferiscono alla determinazione delle proprietà di flessione delle materie plastiche non rinforzate
Il test consiste nel posizionare il provino su una traversa con due punti di supporto completa con una deviazione su un punzone che preme sulla linea centrale del provino, generando così una flessione del provino stesso. È consigliato sempre l'uso di un dispositivo di lettura supplementare della massima deflessione nel punto centrale, in particolare se si deve calcolare il modulo elastico
Fra i materiali generalmente testati si trovano stampi termoplastici e materiali di estrusione, compresi i composti rinforzati e caricati (oltre ai tipi non caricati), lastre rigide termoplastiche, materiali termoindurenti per stampi (compresi composti rinforzati e caricati), fogli termoindurenti. Per i materiali rinforzati è consigliabile valutare altri tipi di norme come ISO 14125 e ASTM D6272