On the improvement measures of interior noise reduction of minivan’s roof based on acoustic modal analysis

In this work, three types of measures, i.e., 1) adding the damping adhesive, 2) changing the local beads and 3) utilizing the dynamic vibration absorber (DVA), are performed to investigate and improve the acoustic quality of the minivan’s interior noise. For adding the damping adhesive, the difference of the adhesive location directly affects the mode of minivan’s roof. For changing the local beads, eight cases of beads are selected. The results indicate that the change trend of the first natural frequency is parabolic as the number of beads increases. For adding the 33 Hz DVA, the results show that the sound pressure levels (SPLs) of the minivan’s response points located at the front, middle and rear seat in the critical frequency are approximately reduced by 2.1 dB, 1.5 dB and 1.1 dB in the minivan’s simulation, and by 2.6 dB(A), 1.4 dB(A) and 2.7 dB(A) in the minivan’s road experiment, respectively. By contrast, the DVA with a certain frequency should be chosen if the reduction of sound pressure level (SPL) is only considered. Furthermore, if the SPL’s reduction and the additional mass are taken into account at the same time, the measure with local flatted beads should be selected. The obtained results could provide a certain practical guiding significance for improving the mode and interior noise of minivan’s roof

A Manufacturing-To-Response Pathway for Formed Carbon Fiber Reinforced Polymer Composite Structures

Over the past decade, there has been an increased adoption of thermoplastic and thermoset based continuous carbon fiber reinforced polymer (CFRP) composites for structural applications in several industries. Among the different manufacturing methods, thermoforming process for thermoplastic based continuous CFRP’s offer a major advantage in reducing cycle times for large scale productions. Similarly, out-of-autoclave curing process for thermoset based continuous CFRP’s using heated tooling enables production of large composite structures. However, these manufacturing processes can have a significant impact on the structural performance of parts by inducing undesirable effects. These effects include inhomogeneous fiber orientations, thickness variations, and residual stresses in the formed CFRP structures. This necessitates the development of an optimal manufacturing process that minimizes the introduction of the undesirable factors in the structure and thereby achieves the targeted mechanical performance. This can be done by first establishing a relationship between manufacturing process and mechanical performance and successively optimizing it to achieve the desired targets. To this end, a few attempts have been made to connect the design, manufacturing, and structural simulation steps in series, by developing virtual process chains (CAE chains) and mapping methods. However, the recent publications implementing these methods are missing some of the relevant effects or steps of the manufacturing process. The present work establishes two Manufacturing-to-Response (MTR) pathways for end-to-end analysis of CFRP composite structures. The current study focuses on establishing a relationship between manufacturing process and mechanical performance. As case studies, the MTR pathway was implemented for 1. thermoplastic based Composite Hat structure manufactured by thermoforming process and 2. thermoset based Composite Boom structure manufactured by Out-of-Autoclave (OOA) molding process using self-heated tool. The pathway primarily comprised of material characterization, finite element simulations and experimental validation. The first case study details the MTR pathway for thermoforming process of Composite Hat structure. Thermoforming process effects were studied and incorporated in structural analysis. The second case study details a framework of the MTR pathway for OOA molding of Composite Boom structure. The first two steps of the pathway namely Composite boom tool design and curing analysis were accomplished as a part of the present study. The MTR pathway(s) were validated experimentally for the Composite Hat structure and validation for the Composite Boom structure is planned for future work. Both studies indicated the significance of incorporating the manufacturing process effects into the structural performance of a composite structure