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Lightweight Components Manufactured with In-Production Composite Scraps: Mechanical Properties and Application Perspectives
Abstract:
In the last years, the design in the automotive sector is mainly led by emission reduction and circular economy. To satisfy the first perspective, composites materials are being increasingly used to produce lightweight structural and semi-structural components. However, the automotive mass production arises the problem of the end-of-life disposal of the vehicle and the reduction of the wastes environmental impact. The circular economy of the composite materials has therefore become a challenge of primary importance for car manufacturers and tier 1 suppliers. It is necessary to pursue a different economic model, combining traditional raw materials with the intensive use of materials from recycling processes. New technologies are being studied and developed concerning the reuse of in-line production scraps with out-of-autoclave process that makes them desirable for high production rate applications.
In this frame, a methodology for the reuse of prepreg cutouts coming from in-line ply cutting process is proposed. Production cutouts (scraps, or chops) are used as a charge to manufacture components through the compression molding process. The structure of the final part keeps in meso-scale the same orthotropic orientation of the chops, although it is quasi-isotropic from a macroscopic point of view. Accordingly, standard three-point bending, and tensile mechanical tests were performed to characterize the mechanical behavior of the material.
Failure modes and fracture propagation were analyzed too. The chop interface resulted to affect the mechanical performance. Before material failure, multiple damage precursor sites nucleated, generally in correspondence of the chop interfaces. Delamination, brittle fracture of the matrix and debonding between the chops were the main failure modes. The results of the standard coupon tests evidenced good performance of the material in terms of strength and stiffness, despite lower than standard 2x2 twill structure, making the studied material suitable for semi-structural purposes. Accordingly, a prototype of an accelerator pedal frame was produced, in order to evaluate the feasibility, the potential limitations and the aspects to be optimized for the manufacturing of a more complex component.