Estimate of the mechanical properties of reinforced polymers

The use of, and demand for, reinforced polymers is growing all the time, in response to the need to lighten and improve the mechanical strength of components. Compared to homogeneous materials, composites are characterized by the fact that the material (in the sense of its microstructure) and the part (materials and shapes) are developed at the same time. An important consequence of this is that the characteristics of the materials are often associated with the part to be produced. Composites are also characterized by the multiplicity of parameters involved in their construction, which means that there is an almost infinite variety of composite materials to choose from, depending on the nature and morphology of the fibers, reinforcements, stacking (angle, thickness, order), resin and reinforcement ratio, not to mention the inevitable presence of defects such as porosities or failure to comply with construction parameters (fiber disorientation, layer thickness, etc.). Several families of reinforced polymers can be defined, differing essentially in morphology (approximated by the form factor) and spatial distribution of the reinforcing phase (random, with preferential orientations, etc.). Structural composites are characterized by the use of continuous fibers organized mainly in unidirectional layers. They exhibit linear or quasi-linear elastic behavior in their field of application. Polymers are also reinforced with chopped fibers or fillers whose spatial distribution can be complex. These composites are characterized by markedly non-linear behavior, with the linear elastic range limited to small deformations. Estimating mechanical properties in the non-linear domain calls for methods that are beyond the scope of this article.

The sheer diversity of reinforced polymers makes it difficult to envisage the creation of a database of mechanical properties, or even a series of abacuses covering the multiplicity of needs, even if efforts in this direction are beginning to appear . Nevertheless, it is useful to have a simple, cost-effective means of assessing the elementary mechanical properties of reinforced polymers used in part design, first and foremost linear elastic behavior, which represents the behavior of structural composites and that of other families of composites at small deformations. A first approach consists of manufacturing the material in the final state of the part, and carrying out an experimental evaluation of properties through standardized mechanical...