This work presents the mechanical behavior of self-reinforced composites (SRCs) manufactured and modified via film stacking. For modification, interleaved films made of polypropylene (PP), a thermoplastic elastomer and a polyolefin engage were combined in different ways to induce the elastic modifier into the matrix material. The content of modifier was also varied in two ways. First, the films were produced out of a single material and second out of a compound. So, the same content of modifier was implemented in two different ways. It is shown that, in case of this research, only the kind of modifier and the content but not the way of implementation are responsible for the mechanical behavior of SRCs. It is shown that the modification can adjust the tensile strength, tensile stiffness and impact properties in a broad range. It is also shown that different mechanical properties of the composite can be predicted by a regression model that uses the Shore A hardness and the content of modifier.

A new process to produce back-injected self-reinforced composites (SRCs) is presented. In contrast to other investigations on back-injection of SRCs, a process is presented which allows compacting and back injection of SRCs in one step where the SRCs are partly consolidated only via melt pressure inside the cavity. The mechanical properties of SRCs depend to a large extent on the process parameters of temperature and pressure during manufacture. These parameters are not yet known for back-injected areas. Sensors inside of the cavity measure the influences on the temperature and pressure conditions in the cavity. Initial studies on adhesion were carried out and analysed. For this purpose, shear tests of the back-injected component were carried out and a maximum shear strength of 5.81 MPa was determined for the materials used here. The investigations also show a dependence on the Distance from the Gate (DG) and the Mass temperature (TM). First microscopic examinations show good bonding between the SRC and the injection molded part, with no voids or air pockets in the boundary layer. It can also be seen that successful consolidation takes place in the area of the back injection.

In this research paper, the effects of the combined compacting and back-injection process to produce back-injected self-reinforced composites on the mechanical properties of the self-reinforced composites (SRCs) are investigated. For this purpose, the parameters barrel temperature, time of injection and holding pressure were varied for the back injection. Tensile and bending tests were carried out on the SRCs. The results show that the mechanical properties depend to a large extent on the process parameters. The measured tensile strength varies between approx. 186 and 86 MPa, the stiffness between approx. 3500 and 2000 MPa. The flexural strength is measured between approx. 75 and 5 MPa, the flexural modulus between approx. 5480 and 650 MPa. Flexural tests are more suitable for evaluation of the consolidation, as tensile tests cannot evaluate the adhesion of the fabric layers to each other in the SRCs. Microscopic examinations show that consolidation by the back-injected melt can lead to smaller cross-sections in the SRCs compared to an area that was not back-injected. At high barrel temperatures, melting of individual fabric layers can occur, which explains, among other things, the drop in the mechanical properties of the SRCs.