The impact resistance of fiber–metal laminates based on glass fiber reinforced polypropylene

The high velocity impact response of a range of fiber–metal laminates (FMLs) based on a woven glass fiber reinforced polypropylene and an aluminum alloy has been investigated. Tests on FMLs, based on 2024‐O and 2024‐T3 aluminum alloys, were undertaken using a nitrogen gas gun at velocities up to 150 m/s. The failure processes in the FMLs were investigated by examining the samples after impact and by sectioning a number of specimens through the point of impact. The impact response of these multilayered samples was also characterized by measuring the residual out‐of‐plane displacement of the targets after testing. Energy absorption in the FMLs occurred through gross plastic deformation, membrane stretching and tearing in the aluminum plies, as well as delamination, fiber fracture, and matrix cracking in the composite layers. In the multilayered FMLs, the permanent displacement at the perforation threshold remained roughly constant over a range of target configurations, suggesting that the aluminum layers deform almost independently through a membrane stretching mechanism during the perforation process. The impact resistances of the laminates investigated were compared by determining their specific perforation energies (s.p.e.), where it was shown that s.p.e. of several of laminates was almost three times that of the corresponding aluminum alloy. The perforation resistances of the FMLs as well as those of the plain composite were predicted using the Reid–Wen perforation model. Here good agreement was noted between the model and the experimental data for the range of laminates investigated here. POLYM. COMPOS. 27:700–708, 2006. © 2006 Society of Plastics Engineers     

The fracture properties of a smart fiber metal laminate

This paper investigates the interfacial, tensile, and fatigue properties of a novel smart fiber‐metal laminate (FML) based on a nickel‐titanium (Ni‐Ti) shape memory alloy and a woven glass fiber reinforced epoxy. Initial tests, using the single cantilever beam (SCB) geometry, have shown that this unique system offers high values of metal‐composite interfacial fracture toughness. Tensile tests have shown that the mechanical properties of these FMLs lie between those offered by its constituent materials and that their tensile modulus and strength can be easily predicted using a rule of mixtures approach. Tension‐tension fatigue tests have shown that the fatigue performance of notched smart FMLs is superior to that offered by the plain Ni‐Ti alloy. A subsequent optical examination of unnotched laminates tested to failure under tension‐tension fatigue loading has shown that the fracture mechanisms occurring within the Ni‐Ti FMLs are strongly dependent on the applied cyclic stress. POLYM. COMPOS., 28:534–544, 2007. © 2007 Society of Plastics Engineers     

The fracture properties of a fiber metal laminate based on a self‐reinforced thermoplastic composite material

The present research program has studied the fracture properties of a Fiber‐Metal Laminate (FML) system constituted by aluminum alloy and a high‐impact self‐reinforced composite material. Here, the self‐reinforced composite system consists of a polypropylene matrix reinforced with polypropylene fibers. Initial testing has shown that a though adhesion can be achieved between the aluminum layers and the composite material by incorporating a thermoplastic adhesive interlayer at the common interface. The adhesion at the metal–composite interface has been studied under a wide range of strain rate conditions using a Single Cantilever Beam test geometry, and it has been shown that the interfacial fracture toughness is loading rate sensitive. Interlaminar delamination tests of the plain composite have also been studied and it was shown that their fracture toughness is also loading rate sensitive. Additional tensile tests have shown that the tensile strength and moduli of the FMLs are linearly influenced by the volume fraction of their constituent materials as well as are successfully predicted using a simple rule of mixture. Low velocity impact tests have also shown that the FMLs based on a self‐reinforced polypropylene composite yielded specific perforation energies well above the 30 J m²/kg. It was also shown that by increasing the number of metal and composite plies in the FMLs, resulted in hybrid structures capable of absorbing higher specific low velocity impact energies. POLYM. COMPOS., 35:427–434, 2014. © 2013 Society of Plastics Engineers     

The influence of different circular hole perforations on interlaminar shear strength of a novel fiber metal laminates

This study characterizes surface treated classic type fiber metal laminates (FMLs) interlaminar shear strength (ILSS) based on a glass mat reinforced polyphenylene sulphide composite and an aluminum alloy. The effect of concentration of γ‐glycidoxypropyltrimethoxysilane surface treatment on ILSS of adhesive bonding between aluminum sheet and composite laminates has been investigated. After determining the silane concentration, novel FML material is manufactured using a compression moulding process which involves aluminum sheets with different circular hole perforations (Array type A and B) with two circular hole diameters (ϕ3 and ϕ5 mm) and two total hole area/closed area: 0.05 and 0.06) to develop mechanical interlocking between aluminum layers and composite laminates. Tensile tests are performed to investigate the effect of different circular hole perforations on ILSS properties of FMLs. Test results show that ILSS is improved with increasing the circular hole diameter and decreased with the number of holes as correlated with undrilled FMLs. Failure modes, damage initiation, and progression of FMLs with different open hole perforations are determined with optical microscope. POLYM. COMPOS., 37:963–973, 2016. © 2014 Society of Plastics Engineers     

Evaluation of adhesion of continuous fiber–epoxy composite/aluminum laminates

Continuous fiber composite/metal laminates (FMLs) offer significant improvements over currently available composite materials for aircraft structures due to their excellent fatigue endurance and low density. Glass fiber–epoxy composite laminae and aluminum foil (GLARE) are commonly used to obtain these hybrid laminates. In this work, FMLs were produced by treating the aluminum foil to promote adhesion bonding by two methods: sulphuric chromic acid etching (SCAE) and chromic acid anodization (CAA). The surface treatments were evaluated by contact angle, roughness and scanning electron microscopy techniques. In order to compare different families of fiber composite/metal laminates, carbon fiber and glass fiber fabrics were used as reinforcements for the hybrid laminates. The adhesion of the hybrid laminates was evaluated by scanning electron microscopy (SEM) and three-point bending test. CAA resulted in better wetting properties. The interlaminar shear strength results for both carbon fiber-epoxy/metal and glass fiber-epoxy metal, were close to the interlaminar shear strength results found in the literature (approx. 40.0 MPa).     

Numerical modeling of the impact response of fiber–metal laminates

This article models the impact response of fiber–metal laminates (FMLs) based on a polypropylene (PP) fiber/PP matrix composite and two types of aluminum alloy. Here, a finite element analysis is used to model the impact behavior of FMLs at velocities up to 150 m/s. The PP‐based composite was modeled as an isotropic material with a specified tensile cut‐off stress to allow for the automatic removal of failed elements. The aluminum was modeled as an elasto‐plastic material with a specified shear failure strain and a tensile failure cut‐off stress. The deformed response of the structures and the resulting failure modes were compared with the experimental data. The variation of the maximum permanent displacement versus normalized impact energy was also predicted and compared with the impact test data and good agreement was observed. Finally, the decay of the kinetic energy of the projectile with time was determined for each of the targets and used to characterize their impact resistance. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

The morphing properties of a smart fiber metal laminate

This article investigates the activation characteristics of a novel fiber‐metal laminate (FML) based on a nickel–titanium (Ni–Ti) shape memory alloy. Initial attention focuses on manufacturing this smart FML in which a woven glass fiber reinforced epoxy material is sandwiched between two shape memory alloy (SMA) outer skins. Activation tests on cantilever beams using a hot air gun have shown that the FMLs exhibits a distinct actuation capability in which beam rotations of up to 11° were recorded. An examination of the edges of polished samples indicated that no damage was incurred by the FML during the activation process. The functionality of the FMLs was enhanced through the introduction of embedded electrical resistance wires located between the composite and metal plies. Here, the embedded electrical wires were heated by passing an electric current through them, thereby activating the SMA plies in a more effective and controllable manner. As before, significant beam tip rotations were recorded in the FMLs in a relatively short time period. Finally, polymer‐based optical fiber (POF) and fiber‐bragg grating (FBG) sensors were introduced into the FMLs in order to monitor their deflection during the activation process. The results of these tests showed that such sensing elements can be successfully employed to monitor the actuation response of these layered laminates. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Interlayer bonding between thermoplastic composites and metals by in-situ polymerization technique

Fiber-metal laminates (FMLs) offer the superior characteristics of polymer composites (i.e., light weight, high strength and stiffness) with the ductility and fracture strength of metals. The bond strength between the two dissimilar materials, composite and metal, dictates the properties and performance of the FMLs. The bonding becomes more critical when the polymer matrix is thermoplastic and hydrophobic in nature. This work employed a novel bonding technique between thermoplastic composites and a metal layer using six different combinations of organic coatings. The flexural, and interlaminar shear strength of the thermoplastic fiber metal laminates (TP-FMLs) were examined to investigate the bond strengths in the different cases along with fracture characteristics revealed from the tested samples using scanning electron microscopy. The viscoelastic performance of the fabricated TP-FMLs were also investigated using the dynamic mechanical thermal analysis method.     

Structure–properties relations in titanium‐based thermoplastic fiber–metal laminates

This paper investigates the interfacial, tensile, and fatigue properties of a titanium alloy fiber–metal laminate (Ti‐FML) based on woven glass‐fiber‐reinforced polyetherimide (GF/PEI). Initial tests, using the single cantilever beam (SCB) geometry have shown that it is not necessary to surface treat the titanium alloy in order to achieve a high value of metal–composite interfacial fracture toughness. Tensile tests have shown that the mechanical properties of the FML lie between those offered by its constituent materials. Tension–tension fatigue tests have shown that the fatigue lives of these laminates are superior to those offered by the plain titanium alloy. The mechanical properties of this glass fiber/PEI FML have also been compared with those offered by an FML based on a unidirectional carbon‐fiber‐reinforced polyetheretherketone (CF/PEEK) composite. Here, it has been shown that although the fatigue properties of this woven GF/PEI composite are inferior to those of the CF/PEEK FML, they do offer a higher temperature capability due to the higher glass transition temperature of the PEI matrix. Polym. Compos. 27:264–270, 2006. © 2006 Society of Plastics Engineers.     

The comparison of low‐velocity impact resistance of aluminum/carbon and glass fiber metal laminates

This article presents the low‐velocity impact response of fiber metal laminates, based on aluminum with a polymer composite, reinforced with carbon and glass fibers. The influence of fiber orientations as well as analysis of load‐time history, damage area and damage depth in relation to different energy levels is presented and discussed. The obtained results made it possible to determine characteristic points, which may be responsible for particular stages of the laminate structure degradation process: local microcracks and delaminations, leading to a decrease in the stiffness of the laminate, as well as further damage represented by laminate cracks and its perforation. The damage mechanism of fiber metal laminates is rather complex. In case of carbon fiber laminates, a higher tendency to perforation was observed in comparison to laminates containing glass fibers. Delaminations in composite interlayers and at the metal/composite interface constitute a significant damage form of fiber metal laminates resulting from dynamic loads. Fiber metal laminates with glass fibers absorb energy mainly through plastic deformation as well as through delamination initiation and propagation, whereas laminates containing carbon fibers absorb energy for penetration and perforation of the laminate. POLYM. COMPOS. 37:1056–1063, 2016. © 2014 Society of Plastics Engineers     

The impact response of aluminum foam sandwich structures based on a glass fiber-reinforced polypropylene fiber-metal laminate

The fracture properties and impact response of a series of aluminum foam sandwich structures with the glass fiber–reinforced polypropylene-based fiber-metal laminate (FML) skins have been studied. Initially, the manufacturing process for producing the FML skins was optimized to obtain a strong bond between the composite plies and the aluminum layers. The degree of adhesion between the composite plies and the aluminum was characterized by conducting single cantilever beam tests. Here, it was found that the composites could be successfully bonded to the aluminum using a simple short stamping procedure. A detailed examination of the fracture surfaces indicated that crack propagation occurred within the composite ply in the fiber-metal laminates and along the composite-aluminum foam interface in the sandwich structures. The low velocity impact response of the FMLs and the sandwich structures was investigated using an instrumented drop-weight impact tower and a laser-Doppler velocimeter. The energy absorption characteristics of the sandwich structures were investigated along with the failure processes. Finally, a series of tensile tests on the damaged FMLs and thermoplastic sandwich structures showed that both systems offer promising residual load-bearing properties. Here, shear failure in the aluminum foam was observed in the sandwich structures, indicative of a strong bond between the FML skins and the aluminum core. Polym. Compos. 25:499–509, 2004. © 2004 Society of Plastics Engineers.     

Structural degradation and mechanical fracture of hybrid fabric reinforced composites

This investigation involves the study of accelerated environmental aging in two polymer composite laminates reinforced by hybrid fabrics based on carbon, Kevlar and glass fibers. Composite laminate configurations are defined as a laminate reinforced with E‐glass fiber and Kevlar 49 fiber hybrid fabric (GK) and another laminate reinforced with E‐glass fiber and AS4 carbon fiber hybrid fabric (GC). Both laminates were impregnated with epoxy vinyl ester thermosetting resin (Derakane 470‐300) consisting of four layers. Morphological studies (photo‐oxidation process and structural degradation) of environmental aging were conducted, in addition to comparative studies of the mechanical properties and fracture characteristics under the action of uniaxial tensile and three‐point bending tests in specimens in the original and aged conditions. With respect to uniaxial tensile tests for both laminates, good mechanical performance and little final damage (small loss of properties) was caused by the aging effect. However, for the three‐point bending tests, for both laminates, the influence of aging was slightly higher for all parameters studied. The low structural deterioration in the laminates is attributed to the high performance with the heat of the matrix (Derakane 470‐300) and the characteristics of the hybrid fabric, exhibiting fiber/matrix interface quality. POLYM. ENG. SCI., 56:657–668, 2016. © 2016 Society of Plastics Engineers     

纤维金属层板铆接损伤机理与预测的研究

纤维金属层板铆接损伤是连接件、被连接件以及铆钉等多个复杂结构的耦合损伤行为。为了预测纤维金属层板铆接损伤行为,采用Johnson-Cook失效准则预测金属层损伤,采用三维Hashin损伤准则预测复合材料层损伤,采用脱层失效理论预测层间开裂,理论预测模型的合理性通过了实验验证。通过损伤预测模型分别考察层板铺层数量、铆接预紧力、铝合金分数和结构几何对纤维金属层板铆接损伤行为及铆接刚度的影响,为FMLs铆接设计提供可行性建议。结果表明:铺层数量的增加加剧了层板自由端层间脱层剥离现象,从而降低了层板铆接强度;铝合金分数的增加能够提高层板的铆接强度,但铝合金分数大于50%时铆接强度和铆接比强度反而下降;预紧力的增大能够延缓纤维和基体的萌生,并且提升铆接刚度,使得纤维金属铆接承受更大载荷;随着横宽径比W/D和纵宽径比E/D的递增,铆接极限强度有所提高,当W/D≥3或E/D≥3时,铆接强度不再明显提高。     

FRTP材料在土木工程制品中的应用研究

FRP材料根据树脂材料的不同分为FRTP（热塑性FRP）和FRSP（热固性FRP）两种；根据FRTP材料自身的物理力学特点，对FRTP材料浸渍与成型工艺、FRTP材料与FRSP材料的物理力学性能比较、土木工程用FRTP筋／板等制品及其物理力学性能及其在土木工程中的国内外应用现状进行了研究；指出了需要进一步研究解决的一些问题。     

Effect of loading‐unloading cycles on impact‐damaged jute/glass hybrid laminates

The production of glass/plant fiber hybrid laminates is a possibility for obtaining semistructural materials with sufficient impact properties, and a better life cycle analysis (LCA) profile than fiberglass. The simplest and possibly the most effective configuration for the production of these hybrids would involve the use of a plant fiber reinforced laminate as the core between two glass fiber reinforced laminates. A main limitation to the use of composites including plant fibers is that their properties may be significantly affected by the presence of damage, so that even the application of a low stress level can result in laminate failure. In particular, it is suggested that when loading is repeatedly applied and removed, residual properties may vary in an unpredictable way. In this work, E‐glass/jute hybrid reinforced laminates, impacted in a range of energies (10, 12.5, and 15 J), have been subjected to post‐impact cyclic flexural tests with a step loading procedure. This would allow evaluating the effect of damage dissipation offered by the plant fiber reinforced core. The tests have also been monitored by acoustic emission (AE), which has confirmed the existence of severe limitations to the use of this hybrid material when impacted at energies close to penetration. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Real‐Time damage detection in thermoplastic‐based composite materials with embedded multi‐mode optical fiber sensors

In this paper we describe the use of an inexpensive standard communication‐grade optical fiber for the purpose of detecting damage in glass fiber reinforced thermoplastic composite materials and hybrid fiber metal laminates based on the same composite constituent. These multi‐mode, step‐index optical fibers were embedded at different locations within the composite structure to assess their ability for structural health monitoring. In this study, the specimens were loaded under a three‐point bend test configuration, Results from the investigation have shown that these optical fibers are capable of detecting the peak failure load in the host material when embedded at locations where structural failure initiates at peak load. The output from the optical fibers was shown to be sensitive to the applied loading conditions suggesting that they can also be used to monitor structural loading. Optical micrographs of selected specimens were obtained by sectioning the specimens at the fracture location to provide confirmation of the optical fiber results.     

Impact behavior of aramid fiber/glass fiber hybrid composites: The effect of stacking sequence

Aramid fiber/glass fiber hybrid composites were prepared to examine the effect of stacking sequence on the impact behavior of thin laminates. The effect of position of the aramid layer on the impact properties of hybrid composites was investigated using driven dart impact tester. The delamination area and fracture surface of hybrid composites were analyzed for correlation with impact energy. The addition of glass layer to aramid layer reduced the impact resistance of hybrid composite due to the restriction in the deformation of aramid layer. The position of aramid layer resulted in variations in the impact behavior of hybrid composites. When the aramid layer was at the impacted surface, the composite exhibited a higher impact energy. This was attributed to the fact that the flexible layer at the impacted surface in thin laminates can experience larger deformation. In three‐layer composites, the aramid fiber‐reinforced composite ( AAA ) exhibited the highest total impact energy due to high impact energy per delamination area (1EDA) in spite of low delamination area. Aramid fiber and glass fiber‐reinforced composites showed a different impact behavior according to the change of thickness. This was attributed to the difference in the energy absorption at interface between laminae.     

Review on impact analysis of FRP composites validated by LS‐DYNA

In recent decades fiber‐reinforced polymer (FRP) materials have revolutionized the world of engineering material. It has emerged as a substitute to traditional engineering material because of its aspect ratio. The increase in demand of FRP in various areas such as automotive and aerospace increases the need to do deep and diversified impact analysis of FRP composites. This article is an attempt to review literatures on the impact analysis of FRP composite validated by LS‐DYNA. The effect of projectile characterization, fiber orientation, and cores on the impact behavior of FRP composite has been discussed. An attempt is done to view literature from 1990s to present days. Because of insufficiency of relevant paper (using LS‐DYNA) in 1990s, this review article includes work done from 2000s to present days. Temperature dependency, energy absorbed, contact time, and damage pattern of the FRP laminates, along with future trend of research work in the area of composite are also discussed. POLYM. COMPOS., 36:1786–1798, 2015. © 2014 Society of Plastics Engineers     

短纤维层间增强碳纤维复合材料层板的力学研究

以斜纹3k T300碳纤维布、环氧树脂和0.3~0.5 mm短切碳纤维为主要实验原料,使用短切纤维铺放装置将短切碳纤维定量铺放在碳纤维布表面,并铺层得到5块层间短切纤维增强的预制体,每块预制体含8层碳纤维布且每块预制体层间短切碳纤维铺放面密度分别为5,10,20,30,40 g/m2,并增设一块层数为8层、层间不含短切纤维增强的预制体作为对照组。采用真空辅助树脂灌注成型方式浸渍预制体后高温固化,得到层间含不同面密度短切纤维的碳纤维复合材料层合板,研究了不同面密度短切纤维含量对碳纤维复合材料层合板拉伸、弯曲以及层间剪切强度的影响。研究结果表明,当短切碳纤维铺放面密度为5 g/m2时,复合材料层板的拉伸、弯曲强度最好,在5~40 g/m2范围内,复合材料层板的层间剪切强度随短切碳纤维铺放面密度的增大而增大。     

Comparison of mechanical and ballistic performance of composite laminates produced from single‐layer and double‐layer interlocked woven structures

Textile structures have become quite popular as reinforcement materials in composite laminates due to their high impact‐damage tolerance and energy absorption ability. The impact performance of textile composites is not only affected by the type of fiber/matrix but also by the fabric structure used as reinforcement. The aim of this study was to compare the mechanical and ballistic performance of composite laminates reinforced with single‐layer and double‐layer interlocked woven fabrics. Kevlar^®−29 multifilament yarn was used for preparation of all the fabric structures and epoxy resin was used as the matrix system. The composites were produced using a hand lay‐up method, followed by compression molding. The mechanical and ballistic performance of composites reinforced with single‐layer and double‐layer interlocked woven fabrics was investigated in this study. The energy absorption and mechanical failure behavior of composites during the impact event were found to be strongly affected by the weave design of the reinforcement. The composites reinforced with double‐layer interlocked woven fabrics were found to perform better than those comprising single‐layer fabrics in terms of impact energy absorption and mechanical failure. POLYM. COMPOS., 35:1583–1591, 2014. © 2013 Society of Plastics Engineers