Performance comparison of resin-infused thermoplastic and thermoset 3D fabric composites under impact loading (original) (raw)
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Impact properties of thermoplastic composites
Textile Progress, 2018
The excellent properties exhibited by thermoplastic composites at much reduced weight have attracted attention in the development of products in different sectors. Thermoplastic (TP) composites, because of their distinctive properties as well as ease of manufacturing, have emerged as a competitor against the conventional thermoset resin-based composites. Depending on the application, these composites may undergo impact events at various velocities and often fail in many complex modes. Hence, the development of TP composites having high energy-dissipation at (the desired) much-reduced weight has become a challenging task, but it is a problem which may be alleviated through the appropriate selection of materials and fabrication processes. Furthermore, fibre surface modification has been shown to increase fibre-matrix interfacial adhesion, which can lead to improved impact resistance. Textile preforms are helpful in acting as a structural backbone in the composites since they offer a relatively free hand to the composite designer to tailor its properties to suit a specific application. Additionally, hybrid textile composite structures may help in achieving the desired properties at much lower weight. Simulation software can play a significant role in the evaluation of composites without damaging physical samples. Once the simulation result has been validated with actual experimental results, it should be possible to predict the test outcomes for different composites, with different characteristics, at different energy levels without conducting further physical tests. Various numerical models have been developed which have to be incorporated into these software tools for better prediction of the result. In the current issue of Textile Progress, the effects of various materials and test parameters on impact behaviour are critically analyzed. The effect of incorporating high-performance fibres and natural fibres or their hybrid combination on the impact properties of TP composites are also discussed and the essential properties of TP polymers are briefly explained. The effects of fibre and matrix hybridization, environmental factors, various textile preform structures and fibre surface modification treatments on the impact properties of thermoplastic composites are examined in detail. Various numerical models used for impact analysis are discussed and the potential applications of TP composites in automobile, aerospace and medical sectors are highlighted.
Impact behavior of a fully thermoplastic composite
Composite Structures
Composites are materials of choice for lightweight structures due to their excellent strength/weight/ and stiffness/weight/ properties. For several years, the application of composite materials with continuous fiber was limited to those with thermosetting matrix. Recently, interest in composites with thermoplastic matrix is growing thanks to their considerable advantages also in terms of recyclability. The thermoplastic composites appear to be the right alternative to the materials currently used, replacing not only the non-structural parts, but also the structural components located in areas potentially subject to impacts. This paper presents the results of an experimental campaign made on a fully thermoplastic composite, where both the reinforcement and the matrix are made in polypropylene. The target is to analyze its behavior under different impact loading conditions using a drop weight testing machine. The influence of the impact mass and of the velocity on the energy absorption capability of the material have been analyzed and discussed. During the tests, the material showed a ductile behavior and developed extended plasticity without a crack tip. The main observed damage mechanisms were the yarn sliding.
Composite Structures, 2017
We present a method to improve the impact damage tolerance of thermoset resin matrix composites by exploiting thermoplastic material impact resistance properties. Two configurations of thermoplastic/thermoset multilayer composites are considered: (a) thermoplastic material is used on sample surface as shock absorber and (b) thermoplastic film is inserted in between thermoset layers to act as interlayer. We aim at increasing adhesion strength between thermoplastic and thermoset resin matrix. We show that mode I critical strain energy release rate, determined by the wedge double cantilever beam fracture test, increases significantly when a third amorphous polymer interlayer compatible with both thermoplastic and thermoset resin is inserted. The analysis of scanning electron microscope fracture surfaces helps us to clarify the adhesion mechanism involved. The high adhesion between thermoplastic and thermoset resins obtained with this method, together with the ability of thermoplastics to dissipate the impact damage in the first plies ensure the reliability of this stacked configuration. Finally, we show that these multilayer composite significantly increases the impact resistance of composite materials.
Experimental investigation on a fully thermoplastic composite subjected to repeated impacts
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2019
In the last years, the spread of composite laminates into the engineering sectors was observed; the main reason lies in higher values of strength/weight and stiffness/weight ratios with respect to conventional materials. Firstly, the attention was focused on fibres reinforced with thermosetting matrix. Then, the necessity to move towards low density and recyclable solutions has implied the development of composites made with thermoplastic matrix. Even if the first application of thermoplastic composites can be found into no structural parts, the replacement of metallic structural parts with such material in areas potentially subjected to impact has become worthy of investigation. Depending on the field of application and on the design geometry, in fact, some components can be subjected to repeated impacts at localized sites either during fabrication, activities of routine maintenance or during service conditions. When composite material was adopted, even though the impact damage ass...
Composite Structures, 2014
This study was aimed at comparing the residual compressive strength and behavior of TS-based (epoxy) and TP-based (PPS or PEEK) laminates initially subjected to low velocity impacts. Provided that the impact energy is not too low, the permanent indentation is instrumental in initiating laminates local buckling under compressive loadings. CAI tests revealed that matrix toughness is not the primary parameter ruling the damage tolerance of the studied materials. However, matrix ductility seems to slow down the propagation of transverse cracks during compression thanks to plastic micro-buckling which preferentially takes place at the crimps in woven-ply laminates. It could therefore justify why the matrix toughness of TP-based laminates does not result in significantly higher CAI residual strengths. Finally, the compressive failure mechanisms of impacted laminates are discussed depending on matrix nature, with a particular attention paid to the damage scenario (buckling and propagation of 0°fibers failure).
Composite Structures, 2017
This paper reports the low velocity impact behavior of thermoplastic laminated structures based on thermoplastic polyurethane reinforced with woven glass fiber highlighting effects related to sample thickness and test temperature with the aim to verify their potential applications. Plaques obtained by film stacking and compression molding technologies are tested using an instrumented falling dart machine at room temperature,-25 °C and-50 °C. Impact results are reported in terms of typical load-deflection and energy-time curves, but also discussed with reference to the well known ductility index (DI) parameter. As expected, the cooling is reflected in an increased stiffness of tested specimens and their higher propensity to the damage. Increases of plate thickness and reductions of the test temperature lead to enhanced friction phenomena at the material-dart contact, responsible of significant deviations from well established semi-empirical models about the Hertz contact force and the penetration energy. Finally, no delamination phenomena seem to be verified for all investigated samples as supported by visual inspections of front and rear impacted areas.
In the course of their “life”, fibre-reinforced plastics (FRP) are subjected to impacts which can cause damage. This damage may lead to a reduction of FRP strength and static load-bearing abilities. In this contribution, new results of three-point flexural tests on glass fibre/polyester composites after non-penetrating ballistic impact are presented. Composite materials were reinforced using a continuous filament mat and a woven roving, and the fibre content varied in the range of 42÷61% wt. The materials were produced using the Resin Transfer Moulding (RTM) method. The impactor was a free-flying 3 g steel ball, and the impact velocities approached 130 m/s. After the impact and evaluation of the extent of damage, the samples were subjected to three-point bending tests under fixed conditions. Reduction in the critical load value was noticed. A novel approach to the evaluation of residual strength has been presented. This approach allows estimation of the actual load-bearing ability of damaged material without removing the undamaged parts of the sample. The said approach involves testing samples including a damaged area as well as undamaged samples. It was considered what effect complete elimination of the damaged field would have on the load-bearing ability of the sample. The load transmitted through the undamaged area surrounding the area of delamination was then subtracted. This allowed for evaluation of the percentage of residual properties in the damaged area. It was found that reinforcement in the form of a continuous-filament mat compares favourably to loose woven roving. Higher-reinforced composites after the impact test seem to lose their properties to a higher extent. Keywords: polymer composites, laminates, unsaturated polyester resin, glass fibre, ballistic impact, residual properties
Glass fibre/polyester composites under ballistic impact
Kompozyty, 2008
This work presents results of ballistic impact tests on glass-fibre/polyester laminates. An effort has been made to manufacture composites with improved tolerance to ballistic impact using inexpensive, common materials like fibreglass and unsaturated polyester resin, by means of modern, yet popular moulding technology. Laminates were made using various E-type glass fibre reinforcements: chopped strand mat, continuous filament mat, cloth and two different woven rovings, with varying weight. Varying number of reinforcement layers were tested, as well as varying reinforcement-to-matrix ratio - from 20 to 60% vol. Samples of manufactured laminates were subjected to impact by a 3 g spherical hardened steel impactor moving at the velocity of 60 and 70 m/s (giving 5.4 and 7.35 Joules of kinetic energy, accordingly) using a gas gun test assembly. Samples were subsequently scanned using optical flat-bed scanner and the obtained images were digitally processed by software to measure the extent of delamination. Two ways of interpreting the extent of delamination in composites were tested - through the evaluation of delaminated volume and through the maximal delaminated surface area - to find usefulness of both methods. Impact energies were kept low such that none of manufactured laminates were perforated. The impact testing and image analysis of delaminated zone has shown similar range of damage in low-weight cloth and continuous filament mat, contrasted to inferior performance of chopped strand mat and high-weight, loose-structure woven rovings. Relationship between coherence of structure and delaminated area reduction has been shown. Unexpected three-dimensional shape of delaminated volume that had been found was discussed. Moreover, two methods of delaminated zone evaluation in composites subjected to impact - by means of delaminated volume and by means of delaminated area - has been discussed, suggesting superiority of the latter. Keywords: composites, laminates, impact testing, RTM, ballistic performance UDAR
2009
High strength 2D fabrics and 3D textile composites comprised of materials such as Kevlar™, Vectran™, Zylon™, and S2-Glass® find applications in protective systems such as personnel armor, spall liners, and turbine fragment containment. Various parameters can significantly affect the response of these fabrics under high rate impact including yarn/tow geometry (cross section), yarn/tow material (modulus, strength), and architecture (undulations and span). However these are just a few of the many other parameters such as projectile characteristics, boundary conditions, number of layers and orientations, weaving degradations, and so forth. Many of these parameters are inter-related and unfortunately this makes a comprehensive study very complex. Therefore, a set of key parameters have been identified for an initial exploratory numerical investigation. These include, on the material front: yarn/tow axial modulus, strength, frictional coefficient; and on the architectural front: yarn/tow ...