Improvement of the Mechanical Properties of GFRP Laminates Used in the Construction of Ship Hulls by Implementing Auxetic Sheet Cores

In this study, a manufacturing process for glass fiber reinforced plastics (GFRP) laminates was developed to improve volume fraction of fibers and mechanical properties. The manufacturing process is combination with wet lay-up and vacuum curing under atmosphere pressure for production of large and complicated structure as a leisure boat and so on. Several kinds of GFRP laminates were produced to consider optimum conditions of the process from viewpoint of volume fraction of fibers and mechanical properties. Volume fractions of fibers in GFRP laminates were measured and cross sections were observed by an optical microscope. The volume fraction in the GFRP laminate made by the suggested method was improved to 41 %, although the one made by conventional wet lay-up method was 17.7 %. Because a lot of large voids included in the laminates were drastically decreased due to the methods. For each laminate, three-point bending test was performed to measure elastic modulus and fracture toughness. Elastic modulus was improved from 5.39 GPa to 8.91 GPa with high volume fractions of fibers. Fracture toughness was improved from 8.19 MPa m1/2 to 16.6 MPa m1/2. Therefore, it was obtained that the method combined with wet lay-up and vacuum curing is easy process for manufacturing large and complicated structure to improve excellent mechanical properties and accuracy of structural shape.

The effect of rolling process on the mechanical and electrical properties of CNTs-enhanced GFRP

Improving tensile properties of glass fiber-reinforced epoxy resin composites based on enhanced multiphase structure: The modification of resin systems and glass fibers

The paper discusses the mechanical and physical behaviour of hybrid glass fibre reinforced plastic (GFRP). Hybrid GFRP was fabricated by three different types of glass fibre, namely, 3D, woven, and chopped, which were selected and combined with mixture of polyester resin and hardener. The hybrid GFRP was investigated by varying three parameters which were the composite volume fractions, hybrid GFRP arrangement, and single type fibre. The hybrid GFRP was fabricated by using open mould hand lay-up technique. Mechanical testing was conducted by tensile test for strength and stiffness whereas physical testing was performed using water absorption and hardness. These tests were carried out to determine the effect of mechanical and physical behaviour over the hybrid GFRP. The highest volume fraction of 0.5 gives the highest strength and stiffness of 73 MPa and 821 MPa, respectively. Varying hybrid fibre arrangement which is the arrangement of chopped-woven-3D-woven-chopped showed the best value in strength of 66.2 MPa. The stiffness is best at arrangement of woven-chopped-woven-chopped-woven at 690 MPa. This arrangement also showed the lowest water absorption of 4.5%. Comparing the single fibre type, woven had overtaken the others in terms of both mechanical and physical properties.

Wood plastic composite (WPC) is a kind of eco‐friendly material made of agricultural and forest industry waste and residues compounded with thermoplastic. The defects of traditional WPC, such as low strength and high creep, greatly limit its engineering applications. To solve the problem, this paper proposed two methods of glass fiber reinforced polymer (GFRP) reinforced PVC‐based WPC panels (G‐WPC) by bonding GFRP sheets or embedding GFRP bars in the tensile zone of the WPC panels. The effects of the thickness of GFRP sheet and reinforcement ratio of GFRP bar on the flexural property of G‐WPC were comparatively analyzed by carrying out four‐point bending tests and finite element simulations. The results showed that the failure modes of the GFRP sheets reinforced specimens were mainly flexural fracture and interface debonding, and the GFRP bars reinforced specimens were flexural fracture and excessive deformation. The ultimate flexural bearing capacity of both GFRP sheets/bars reinforced specimens could be improved by more than 200%. GFRP bar reinforced specimens had better ductility than reinforced with sheet. The effects of WPC density, GFRP sheet fiber layup angle and GFRP bar diameter on the flexural behavior of G‐WPC were further parametrically analyzed using the finite element model (FEM). Highlights Two effective flexural reinforcement methods of WPC were proposed. The optimum thickness of GFRP sheet was obtained based on experimental tests. The suitable reinforcement ratio of GFRP bars was studied by tests and FEM. Effects of WPC density, GFRP fiber layup angle and bar diameter were analyzed.

Glass fiber reinforced polymer (GFRP) composites offer several advantages over welded steel plate connections when used in the connection of vertical joints between concrete wall panels. These advantages include resistance to corrosion, higher tensile strength, and ability to conform to uneven surfaces. In the present research, push-off tests and wall tests were carried out to understand the behavior of GFRP composite connections between concrete elements. Push-off tests were performed to understand direct shear transfer capability when using different concrete surface preparation methods. Wall tests were performed to understand the behavior of different GFRP composite connections under simulated seismic loads, or cyclic shear. Ultimately, the GFRP composite connections displayed little ductility, but demonstrated outstanding displacement and load capacity. Push-off tests were performed for a GFRP composite connection between two L-shaped concrete elements. Each of the six groups of surface preparation included three specimens each, resulting in eighteen push-off specimens. A compressive load at the top and bottom of the specimen introduced direct shear in the GFRP composite connections. Specimens with concrete surface preparation using only a high-pressure wash demonstrated superior load and displacement capacities. Wall tests were performed for GFRP composite connections between two concrete panels, with the connection only applied on one side of the joint. A lateral load was applied at the top of the wall pair, while restraining the horizontal movement at the base and the vertical movement of each panel, inducing shear in the connection. Tests from group one (using unidirectional lamina) included eight specimens and concluded that the use of application pressure and CFRP anchors significantly increased load, displacement, and shear capacity of the GFRP composite connection. Also, fewer layers and CFRP anchor use increased the amount of energy dissipated during simulated seismic loads. Tests from group two (using bidirectional lamina) included six specimens and concluded that the use of GFRP anchors significantly increased load, displacement, and shear capacity of the GFRP composite connection. Also, the use of epoxy-putty adhesive had a significant effect on the load capacity; and full seam coverage and GFRP anchor use increased the amount of energy dissipated during simulated seismic loads.

The aim of this research was focused on the relationship between the skill of an operator in the hand lay-up molding method and the mechanical properties of the molding composites. Glass fiber reinforced plastic (GFRP) plates were prepared using the hand lay-up method by five inexperience operators. The materials of GFRP included unsaturated polyester resin and chopped glass fiber mat. The working procedure of all operators was recorded by a video camera. Mechanical properties of the GFRP plates were carried out by tensile testing. The load-displacement curve was illustrated, which was used for characterizing the molding technique of various operators. The relationship of working times and mechanical strength of the GFRP was characterized, which impacted on the mechanical properties of the specimens. From the results, the relationship was considered separately in the first half and the second half of the working times. From the results, the step of degassing squeeze out air was significantly influenced the mechanical strength of the GFRP products. Therefore, the degassing step with the iron bar was the most affected on the mechanical properties of the GFRP plate making by the inexperience operator. It can be noted that the fully degassing out of the molding product strongly suggested for the hand lay-up method in order to maintain the high strength of the GFRP products.

본 연구에서 교량바닥판용으로 조립식(Modular) 유리섬유 보강(GFRP) 바닥판의 개념을 제안하였다. 본 조립식 GFRP 바닥판시스템은 GFRP 주 단위모률(unite module)과 연결 단위모듈로 구성되어 있다. 본 GFRP 바닥판의 구조성능을 평가하기 위해 정적하중실험을 실시하였다. 그리고 구조성능 결과에 대해서 범용 유한요소 프로그램인 LUSAS을 이용한 수치해석 결과와 비교 분석하였다. 본 연구에서 제안한 조립식 GFRP 바닥판은 교량적용에 매우 유용할 수 있음을 확인할 수 있었다. 제안된 GFRP 바닥판의 파괴모드가 개발된 다른 상용화된 GFRP 바닥판의 파괴모드와 매우 유사한 파괴모들 나타내었다. A concept of Modular GFRP(Glass Fiber Reinforced Polymer) deck panel was proposed for bridge decks. The modular GFRP bridge deck system is comprised of main unit module and connector unit module with GFRP flanges and web. Its structural performance under static loading was evaluated and compared with the LUSAS finite element predictions. It was found that the presented GFRP modular panel was very efficient for use in bridges. The failure mode of the proposed GFRP deck was similar when compared with that of commercial other GFRP decks developed.

Fatigue life reduction of GFRP composites due to delamination associated with the introduction of functional discontinuities

Laminated fiber reinforced polymers (FRP) have excellent in-plane stiffness and strength, but suffer from transverse impact loading due to the lack of fiber reinforcement in that direction. Under transverse impact, extensive delamination can occur in the interlaminar resin-rich regions, which leads to a reduction of stiffness and strength. Therefore, many researchers have attempted to establish a standard testing method that characterizes the interlaminar fracture toughness for delamination [1]. In addition to the measurement of the delamination toughness, analysis of the fracture surface using optical microscopy or scanning electron microscopy (SEM) can also provide useful information for the delamination resistance characterization. Recently, we have evaluated mechanical properties of two glass-fiber-reinforced polymers (GFRP) [2], using transverse impact, double cantilever beam (DCB) and end-notched flexure (ENF) tests. Results from the transverse impact and DCB tests showed a clear difference in delamination resistance between the two GFRP, but such a difference was not found from the ENF test. Based on the ENF test results, the two GFRP should have similar delamination resistance in the shear mode (Mode II). Although this discrepancy in delamination resistance may be caused by the toughness variation in different modes of loading, we believe that the discrepancy is mainly due to a problem with the ENF test for the characterization of the delamination resistance. This issue has been raised in several studies [3, 4], and is further investigated here through the examination of fracture surfaces to provide additional evidence. Two GFRP used in this study have polymer matrices that are the same as those used previously, that is, isophthalic polyester (TMR300 isopolyester, provided by Viking Plastics, Edmonton) and polyurethane-based resin (PUL-G polyurethane, provided by Resin System Inc., Edmonton). The PUL-G polyurethane resin contains 15% CaCO3 particulates for stiffness enhancement. For convenience, the two GFRP will be named PI-GFRP and PU-GFRP in this paper, for isopolyesterbased GFRP and polyurethane-based GFRP, respectively. The glass fiber used is 9-oz/yd2 warp, unidirectional woven fabric (provided by ZCL Composites, Edmonton) which consists of parallel fiber bundles stitched together with a gap of around 1 mm. The gap between the fiber bundles generated resin-rich zones in the GFRP. Therefore, the GFRP have resin-rich zones in the intra-laminar, inter-fiber-bundle regions and the interlaminar regions. GFRP plates of nominally 6.0 mm thick were fabricated using a resin transfer molding (RTM) technique. The fiber lay-up of the transverse impact specimens is [(0/90)5]s, and that of the DCB and ENF specimens is [(0/90)402]s of which the four central 0-degree layers were to provide a uni-directional fiber environment in the direction of crack growth, in accordance with most of the test coupons used in the past. The specimens for DCB and ENF tests contain an aluminum insert film, 15 μm thick, that is placed between the 2nd and the 3rd of the four central layers, acting as a starting defect for delamination crack growth. Dimensions of the specimens are 93 × 93 mm2 for the transverse impact test, and 120 × 20 mm2 for the DCB and ENF tests. Overall fiber volume fraction of the specimens is around 40%, estimated using the following equation [5]:

Although GFRP has a much higher strength-to-weight ratio than conventional materials such as steels and concrete, it suffers from poor “local” resistance to the indentation damage, often introduced by transverse point loading. This is due to the inherent in-plane reinforcement of fiber, which does not provide any strengthening of the GFRP in the out-of-plane direction. Most of the indentation damages generated by transverse loading appear to be small, with a size similar to the contact area, thus being deemed to have little effect on the over-all properties of the GFRP. Consequently, little attention has been paid in the past to understand how material parameters of the GFRP affect its resistance to the indentation. This concept, however, is being challenged by applications such as boat hulls and bridge decks that use thick GFRP laminates. For these types of applications, indentation damage is the most common mechanism that initiates damages such as delamination under the contact surface [1–3], causing significant loss of structural integrity and possibly catastrophic failure. Most research work on indentation of fiber composites [4–6] dealt with damages that were a combination of local indentation and sub-surface delamination. This was because specimens used were not stiff enough to prevent delamination under the contact point. Therefore, the results failed to isolate the indentation damage from other fracture mechanisms, producing information that was not applicable when knowledge of pure indentation damage was required. As the first step to characterize fiber composite’s resistance to indentation damage, a series of experiments were conducted to measure energy absorbed by fiber composites that were subjected to pure indentation damage. This paper summarizes results from the indentation tests, and discusses its significance in over-all energy absorption of GFRP under transverse loading. The two GFRP used in the study have the same fiber volume fraction and lay-up, but different resins for the matrix. One resin was pure isophthalic polyester (TMR300 iso-polyester, provided by Viking Plastics, Edmonton) and the other polyurethane resin with 15% CaCO3 particles (PUL-G resin, provided by Resin Systems Inc., Edmonton). The fiber used was warp unidirectional glass fiber fabric of 9 oz/yd2, which consists of unidirectional fiber bundles that are held in parallel at a distance of approximately 1 mm apart by stitching thread [7]. The fiber lay-up is [(0/90)5]s that forms a nominal specimen thickness of 6 mm with the maximum variation of ±0.05 mm. A resin transfer molding technique was used for the GFRP fabrication to ensure consistent thickness of the test coupons. Due to the inter-fiber-bundle gap, resinrich zones exist in the laminates, in the inter-laminar regions and the intra-laminar, inter-fiber-bundle regions. Overall fiber volume fraction of the GFRP was estimated to be around 40%, based on the following equation [8]

The ore and rock mass of Jinshandian iron mine is very cracked, the problem of development working failure is serious, the metal bolts supported failed is serious because of corrosion. Because of the good characteristics of glass fiber reinforced polymer (GFRP) anchor, the paper study of using GFRP bolt supporting to replace screw-thread steel bolt supporting. Based on the GFRP bolt supporting industrial test and monitoring in Jinshandian iron mine, the paper analysis the testing tunnels convergence deformation and discusses the GFRP bolt supporting problems in Jinshandian iron mine. Experiments show that, in Jinshandian Iron Mine using GFRP bolt or screw thread steel anchor supporting can achieve the same effect in controlling the deformation of tunnel, but the tail of GFRP bolt destroyed easily under blasting shock effect, and the nut easily shedding under the large tunnel deformation effect. Because of the reasons the GFRP bolt can not failed can not continue to provide effective extrusion pressure and the metal net fall off until the entire bolt failure. Furthermore, the GFRP bolt easily bending failure in the high ground pressure area. But from the whole testing development working stability, the GFRP bolt supporting tunnel is feasible in Jinshandian iron mine.

Glass Fiber Reinforced Plastic (GFRP) composites as rolled bars can be used as steel rebar to prevent oxidation or rust which is one of the main reasons concrete structures deteriorate when exposed to chlorides and other harmful chemicals. GFRP is successful alternative for reinforcement with high tensile strength- low strain, corrosion resistance and congenital electromagnetic neutrality in terms of longer service life. The main goal of the study is to investigate the mechanical and bonding properties of GFRP bars and equivalent steel reinforcing bars then compare them. GFRP and steel rebar are embedded in concrete block with three different levels. Mechanical properties of GFRP and steel bars in terms of strength and strains are determined. On the other hand; modulus of elasticity of GFRP and steel bars, modulus of toughness and modulus of resilience were calculated using stress-strain curves, as a result of the experiments. Pull-out tests are conducted on each GFRP and rebar samples which are embedded in concrete for each embedment level and ultimate adherence strengths are determined in terms of bar diameter–development length ratio. Yield strength, strain and modulus of elasticities of GFRP samples are compared to steel rebar. According to the test results reported in this study, GFRP bars are used safely instead of steel bars in terms of mechanical properties.

Synthesis of Al and Cu wires embedded glass fiber reinforced polymer (AWGFRP and CWGFRP) composites and their mechanical characterization

Behaviour of hybrid FRP-timber thin-walled Cee section columns: an experimental and numerical investigation