ISO 75-3:2004规定了一种测定纤维长度大于7.5 mm的高强度热固性层压板和模压长纤维增强塑料在载荷下挠度温度的方法。如ISO 75-2所示，使用的弯曲应力不是固定的，而是受试材料初始（室温）弯曲模量的一部分（1/1000）。这使得该方法适用于具有广泛弯曲模量的材料。

ISO 75-3:2004 specifies a method for the determination of the temperature of deflection under load of high-strength thermosetting laminates and compression-moulded long-fibre-reinforced plastics in which the fibre length is greater than 7,5 mm. The flexural stress used is not fixed, as in ISO 75-2, but is a fraction (1/1000) of the initial (room-temperature) flexural modulus of the material under test. This allows the method to be applied to materials with a wide range of flexural moduli.