Processing‐properties relationship of sandwich panels with polypropylene‐core and polypropylene‐matrix composite skins

Passaro, Alessandra; Corvaglia, Paolo; Manni, O.; Barone, L.; Maffezzoli, Alfonso

doi:10.1002/pc.20025

Cited by 33 publications

(23 citation statements)

References 6 publications

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“…23,24 The results reported in Figure 4 indicate that the material can be successfully processed at very low pressures (down to 1 × 10 −2 MPa).…”

Section: Compression Testsmentioning

confidence: 80%

“…Above 175 • C, a further thickness decrease can be observed, indicating that the compaction process can be regarded as a two-stage process, the first relating to fiber impregnation, and the second to void reduction and expulsion from the laminate boundaries. 23,24 The results reported in Figure 4 indicate that the material can be successfully processed at very low pressures (down to 1 × 10 −2 MPa).…”

Section: Compression Testsmentioning

confidence: 94%

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A preliminary study on bladder‐assisted rotomolding of thermoplastic polymer composites

Salomi

Greco

Felline³

et al. 2007

Adv Polym Technol

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ABSTRACT:In this preliminary work, a new process is examined for manufacturing hollow parts from continuous fiber-reinforced thermoplastic polymer. The new process combines the basic idea of bag forming (or bladder-assisted forming) with the rotation of the mold for the processing of thermoplastic matrix composites. A pressurized membrane is used to compact the composite on the inner wall of a mold, which is placed inside a forced convection oven. The mold is removed from the oven for the cooling stage. The process was initially developed by using a thermoplastic pre-preg obtained using yarns of commingled E-glass fibers with isotactic polypropylene (iPP). A preliminary characterization of the thermoplastic composite showed that the material can be consolidated with pressures as low as 0.01 MPa, which is readily ROTOMOLDING OF THERMOPLASTIC POLYMER COMPOSITESachievable with the process of this study. The design of the mold and membrane was carried out on the basis of both structural analysis of the aluminum shell and thermal analysis of the mold. The mold thickness is of great importance with respect to both the maximum pressure allowed in the process and the overall cycle time. Molding was performed on stacks of three and six layers of yarn, varying the applied pressure between 0.01 and 0.05 MPa and maximum temperature of the internal air between 185• C and 215• C. The composite shells obtained under different processing conditions were characterized in terms of physical and mechanical properties. Mechanical properties comparable with those obtained by compression molding and vacuum bagging were obtained. The maximum values obtained are 12.1 GPa and 290 MPa for the flexural modulus and the flexural strength, respectively. Furthermore, the results obtained show that mechanical properties improve with increasing the pressure during the cycle and with the maximum temperature used in the process.

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“…23,24 The results reported in Figure 4 indicate that the material can be successfully processed at very low pressures (down to 1 × 10 −2 MPa).…”

Section: Compression Testsmentioning

confidence: 80%

Section: Compression Testsmentioning

confidence: 94%

A preliminary study on bladder‐assisted rotomolding of thermoplastic polymer composites

Salomi

Greco

Felline³

et al. 2007

Adv Polym Technol

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“…Continuous fiber reinforced thermoplastic matrix composites, based on commodity polymers, are attracting a growing interest, essentially, thanks to their processability, high impact and delamination strength, abrasion and chemical resistance, low moisture absorption, unlimited shelf life of raw materials, and low cost. In addition, the ability of thermoplastic matrix com-posites to be recycled is one of the main advantages over the thermosetting matrix composites in the automotive industry [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Assessment of the relevance of sintering in thermoplastic commingled yarn consolidation

et al. 2011

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The aim of the present article is to study the different phenomena which are at the basis of the consolidation of commingled thermoplastic semi‐pregs made of amorphous polyester fibers and E‐glass reinforcement. The evolution of the void fraction during the consolidation of the composite was monitored by a dynamometer, equipped with parallel plates and a forced convection oven. Different physical changes were associated to the consolidation temperature. Scanning electron microscopy (SEM) and thermomecahnical analysis (TMA) showed that at low temperature, matrix fiber deformation and sintering are responsible of the initial void reduction. At a temperature higher than the onset of the flow region, reinforcement impregnation is responsible of the further void reduction. Dimensionless analysis confirmed that at lower temperatures, corresponding to higher viscosities, consolidation due to viscous flow of the polymer matrix is negligible compared to consolidation due to sintering of matrix fibers. The results indicate that the Darcy law can efficiently represent the consolidation during the microscale impregnation of the reinforcement, but cannot account for the initial stages of consolidation. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

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“…During the forming process, the material is formed between matched dies, while the flow of the matrix wets out the fibers, as a result of the applied pressure and temperature. Many experimental studies have dealt with the correlation between molding parameters and the final properties of composites,3–5 often neglecting the mechanism of fiber impregnation. In contrast, many theoretical and experimental studies have been devoted to the principles of the flow mechanism of thermosetting resins in RTM‐like processes, mainly using the Darcy approach 6,7.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of the microscale impregnation in commingled thermoplastic composite yarns

2010

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ABSTRACT:The impregnation of a glass woven fabric with an amorphous polyethylene terephthalate copolymer (PET-g) matrix was investigated using a finite element (FE) model for interbundle and intrabundle flow of the matrix. Micrographs of samples obtained by film stacking of PET-g to impregnate the glass fabric have confirmed the occurrence of interbundle and intrabundle flow, taking place as separate steps. On the basis of this evidence, two different mechanisms for the fiber impregnation were postulated. The first flow process is associated with a macroscale interbundle impregnation, whereas the second is associated with microscale intrabundle impregnation. Two different FE models were developed to simulate the microscopic and macroscopic flow of the matrix, considering a large number of different random fiber arrangements. Both models could account for the non-Newtonian rheological behavior of the thermoplastic matrix. The microscale impregnation of fibers was simulated by using randomly spaced and nonoverlapping unidirectional filaments. The effect of the number of filaments and the number of random distributions necessary to achieve an adequate accuracy of the method was assessed. The results obtained from the simulation showed that at low pressures, the polymer melt exhibits Newtonian behavior, which makes it possible to predict the tow permeability by the Darcy law. A more difficult situation arises at high pressures because of the Correspondence to: A. Maffezzoli;

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Processing‐properties relationship of sandwich panels with polypropylene‐core and polypropylene‐matrix composite skins

Cited by 33 publications

References 6 publications

A preliminary study on bladder‐assisted rotomolding of thermoplastic polymer composites

A preliminary study on bladder‐assisted rotomolding of thermoplastic polymer composites

Assessment of the relevance of sintering in thermoplastic commingled yarn consolidation

Numerical simulation of the microscale impregnation in commingled thermoplastic composite yarns

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