Influence of Pressure and Temperature on the Strength Properties of a Laminate Produced by the RTM Method

This paper discusses the effect of pressure on the content of microvoids and defects inside laminates fabricated under different pressures, by vacuum methods. Two basic vacuum methods resin transfer molding (RTM) and vacuum bag method were used in this paper. A glass mat with an alignment angle of (0□/90□) and a mass of 450 g/cm2 was used to produce the laminate, and a polymer resin was used as the matrix. Special attention was paid to the technological parameters of both processes. A mathematical analysis of the most important parameters which include flow rate, permeability, and gelation temperature has been carried out. In addition, the resin temperature is used to reduce the viscosity of the resin to facilitate its flow through the reinforcement, and in the final stage of production to control the chemical reactions occurring in the mold. The pressure is chosen so that the resin flow is continuous. The synchronization of these two parameters and the measurement of the time in which they occur are called the “cure cycle”. In the final step of the study, the composite was subjected to a static tensile test, using specimens of two different dimensions (scale effect) to evaluate the effect of microvoids and microcracks created by the processes on the strength of the material.

A Sequential Approach for Simulation of Thermoforming and Squeeze Flow of Glass Mat Thermoplastics

In this study, a sequential thermoforming and squeeze flow simulation approach for Glass Mat Thermoplastic (GMT) material is proposed and applied to a hat section geometry using input properties based upon Tepex flowcore, a long glass fiber reinforced polyamide (PA/GF) mat manufactured by Lanxess. First, a fully-coupled thermomechanical simulation is conducted based on a purely Lagrangian description, to efficiently capture thermoforming. Subsequently, relevant state variables are mapped and initialized for a Coupled-Eulerian-Lagrangian (CEL) approach. The CEL approach is adopted to accurately capture squeeze flow, which is not possible by a purely Lagrangian description. While numerical techniques differ, both approaches use the same three-dimensional and thermomechanical constitutive equations including an equation of state, a nonlinear viscosity model, and crystallization kinetics, implemented through a material user-subroutine (VUMAT) for the commercially available simulation software package ABAQUS/Explicit.

Process- and material-induced heterogeneities in recycled thermoplastic composites

A novel recycling solution for thermoplastic composites (TPCs) was recently implemented. The processing steps comprise shredding of TPC offcuts to flakes of a few centimetres, melting and blending of the flakes in a low-shear mixer, extrusion of a molten mixed dough and subsequent compression moulding in a press. This material and process are similar to the compression moulding of long-fibre thermoplastics (LFTs) that have been in the market for decades, such as glass mat thermoplastics (GMT) or direct-LFT. However, the input material in this recycling route consists of multi-layered woven flakes, which is very different from the pellets or chopped rovings of other LFTs. Process- and material-induced heterogeneities such as fibre orientation, percolation, variation of fibre fraction, or fibre attrition may be different for this new material. The development of this recycling technology and future industrial applications require more confidence in the material and process. The objective of this study is to characterise these heterogeneities for this recycling solution, and compare them to those generated in regular LFTs. It was found that the process- and material-induced heterogeneities of the recycled TPCs are similar to other LFTs, for the aspects listed here: fibre orientation, percolation, variation of fibre fraction and fibre attrition. In comparison to GMT, the effect of the mixing step is particularly noticeable on the local variation of fibre fraction within the panels. Industrial applications of this recycling route will benefit from this similarity, as it improves the confidence in the material and process combination.

Biomolecule-guided cation regulation for dendrite-free metal anodes

Lithium (Li) or zinc (Zn) metal anodes have attracted interest for battery research due to their high theoretical capacities and low redox potentials. However, uncontrollable dendrite growth, especially under high current (>4 mA cm−2), precludes reversable cycling in Li or Zn metal batteries with a high-loading (>4 mAh cm−2), precludes reversable cycling in Li or Zn metal batteries with high-loading (>4 mAh cm−2) cathode. We report a cation regulation mechanism to address this failure. Collagen hydrolysate coated on absorbed glass mat (CH@AGM) can simultaneously induce a deionization shock inside the separator and spread cations on the anode to promote uniform electrodeposition. Employing 24 mAh cm−2 cathodes, Li and Zn metal batteries with CH@AGM delivered 600 cycles with a Coulombic efficiency of 99.7%. In comparison, pristine Li and Zn metal batteries only survive for 10 and 100 cycles, respectively. This approach enabled 400 cycles in a 200 Ah-class Zn metal battery, which suggests a scalable method to achieve dendrite-free anodes in various batteries.