Flatwise Directions Research Articles

Evaluation of tensile and flexural properties of woven glass fiber/epoxy laminated composites oriented in edgewise and flatwise directions

In this study, the tensile and flexural properties of skin-core-skin woven glass fiber/epoxy laminated composites were conducted. Six plies (laminae) for the skins and twenty-four plies for the core were hand-laid up. All plies used had the same dimensions and the same elastic strength where the skins’ plies kept in flatwise direction while the core’s plies oriented in edgewise and flatwise to study the effect of plies alignments and hence loading direction i.e., edgewise (in-plane) and flatwise (out-of-plane) on the materials characteristics. It was observed that the composites oriented in edgewise position had the highest strength of 186 MPa (enhancement 59%) and deformed at higher loads with minor displacements compared to the flatwise strength of 117 MPa. The SEM analysis of the tensile’s fracture surface showed two dominant toughening mechanisms are debonding (fiber pullout) and fiber breakage, while interlaminar/intralaminar delaminated yarns was observed in the flexural fracture surface.

Effect of graphene nano-platelets on mechanical and impact characteristics of carbon/Kevlar reinforced epoxy hybrid nanocomposites

The influence of various graphene nano-platelets (GNPs) content on the tensile, flexural and Charpy impact characteristics of carbon, Kevlar and hybrid carbon/Kevlar fibers reinforced epoxy matrix composites was investigated. Both of composite configurations as carbon and Kevlar at outer and core skins were experimentally tested. The SEM images for flexural specimens were taken to observe the adhesion mechanism of GnPs particles with fiber/epoxy system. It is found that hybridization with Kevlar layers is contributed a positive effect on the hybrid carbon/Kevlar laminate structures in terms of tensile, flexural and impact behaviour. The incorporation of GnPs particles in hybrid and non-hybrid composite samples results in significant improvements in tensile, flexural and impact properties, and the greatest improvement occurs within the GnPs particle content of 0.1 and 0.25 wt%, indicating that the interfacial bonding between the matrix and the fibers is better due to the large surface area of the GnPs and the good entanglement between the GnPs layers and the matrix chains. The samples of impact test are experimented for edgewise and flatwise directions.

Nondestructive Evaluation of 2 by 8 and 2 by 10 Southern Pine Dimensional Lumber

Abstract This study investigated the use of two nondestructive testing (NDT) methods to evaluate the mechanical properties of No. 2 grade: 2 by 8 and 2 by 10 southern pine lumber. The dynamic modulus of elasticity (dMOE) of each specimen was evaluated nondestructively by using longitudinal vibration and transverse vibration in edgewise and flatwise directions. After the NDT evaluation, the specimens were destructively tested and correlations between static bending MOE with modulus of rupture (MOR) and dMOE were developed. The overall MOE values were 11.14 and 10.96 GPa for 2 by 8 and 2 by 10, respectively. For MOR, the overall value for 2 by 8 was 42.59 MPa, and for 2 by 10 was 43.05 MPa. As expected, results showed statistically significant correlations between static MOE and dMOE (with r ranging from 0.87 to 0.96 for both sizes tested). Also as expected, weaker correlations were found between MOR and the dMOE values (with r ranging from 0.42 to 0.57 for both sizes tested). The lower correlations are largely explained by the difference between the NDT tools analyzing each specimen's global stiffness versus MOR, which is influenced heavily by localized characteristics. Perhaps this finding occurred because larger strength-reducing characteristics are permitted in larger section pieces (2 by 8 vs. 2 by 10) and thus they have opportunity for greater variability. The continuation of studies to develop more reliable NDT is crucial to improve the evaluation of mechanical properties of southern pine lumber and is beneficial to the southern pine timber industry.

Assessing Southern Pine 2x4 and 2x6 Lumber Quality: Longitudinal and Transverse Vibration

A primary goal of structural lumber grading is the identification of the strength-reducing characteristics that impact the modulus of rupture (MOR). Non-destructive evaluation technology can be used to identify material of greater stiffness. This study investigates the use of longitudinal and transverse vibration methods to evaluate the mechanical properties of 2x4 and 2x6 southern yellow pine lumber. A total of 1240 samples were conditioned to 12% equilibrium moisture content. All samples were first non-destructive tested using transverse vibration equipment (Metriguard E-computer) in edgewise and flatwise directions and three different longitudinal vibration devices (Fakopp Portable Lumber Grader, Director HM200, and Falcon A-grader) to obtain the vibration properties using transverse and longitudinal methods. The dynamic modulus of elasticity (MOE) of each sample was calculated based on the fundamental wave equation. Static bending was subsequently conducted according to ASTM 198 (2012), and the rate of loading followed ASTM D4761 (ASTM 2012). The results showed statistically significant correlations between static MOE and the dynamic MOE measured by non-destructive techniques. Weaker correlations were found between MOR and the dynamic MOE values. Likely this finding is because it is related to the ultimate strength of material, often associated with the existence of localized defects, such as a knot, on the lumber piece. This study indicates that non-destructive techniques can potentially be used to evaluate 2x4 and 2x6 stiffness and improvements can be done for a better evaluation of southern pine lumber.

Bending performance of GFRP-wood sandwich beams with lattice-web reinforcement in flatwise and sidewise directions

This paper investigates the flexural behaviors of novel composite sandwich beams that feature Paulownia or Southern pine wood core and glass fiber reinforced polymer (GFRP) face-skins reinforced with lattice-webs. A vacuum-assisted resin infusion process was employed to mold sandwich beams with different numbers of webs. Two control wooden beams and eighteen lattice-web reinforced sandwich beams were subjected to four-point bending to determine their stiffness, load capacity, and failure mechanisms in the flatwise and sidewise directions. The experimental results revealed that the composite sandwich beams in flatwise bending tests failed under a lower load but yielded a larger deflection than those in sidewise bending tests. With an increase in the number of lattice-webs, pseudo-ductility was found to increase in the flatwise directions but decrease in the sidewise directions. Analytical equations were developed for calculating the bending stiffness, load capacity, and pseudo-ductility of the GFRP-wood sandwich beams, and the corresponding analytic results were found in good agreement with the experimental results.

Design and Experimental Study of a Model Magnet for Spiral-Sector FFAG Accelerators

A project to develop fundamental technologies for accelerator magnets using high- $T_{c}$ superconductors is currently underway. In this project, conceptual design studies of fixed-field alternating gradient (FFAG) accelerators for carbon cancer therapy and for accelerator-driven subcritical reactors have been carried out. To establish technologies for cryocooler-cooled high- $T_{c}$ superconducting (HTS) accelerator magnets wound with coated conductors, a downscaled model magnet system for a spiral-sector FFAG accelerator has been developed. A model magnet consisting of multiple coils with complicated shapes, including a negative-bend part or a 3-D bent part, was designed to demonstrate the generation of an asymmetrical magnetic field on the midplane of the magnet bore. One issue is how to wind coils for the accelerator magnets by using tape-shaped coated conductors, which have anisotropic bending flexibility between the flatwise and edgewise directions. Another issue is the effects of the characteristic features of the coated conductors on the accuracy of the magnetic field. The field precision of coils wound with coated conductors is considered to be influenced by the dimensional accuracy of the YBCO tapes and coils, as well as the magnetization of the HTS layer. This paper describes the design and fabrication of YBa2Cu3Ox coils for the model magnet, as well as disturbance factors of the field of the HTS magnet and the effect of dimensional variations of the YBCO coil on the magnetic field.

Experimental and Computational Investigations of Creep Responses of Wood/PVC Composite Members

Abstract This article reported on finite element simulation to predict the creep responses of wood/poly (vinyl chloride) (WPVC) composite members before and after strengthening by using high carbon steel (HCS) flat bar strips bonded to the tension side of composite members. The short-term properties and creep characteristics, in accordance with power law models of WPVC composites and HCS flat bar materials, were determined individually by extensive experimental investigations. The experimental results indicated that strengthening of WPVC composites with HCS flat bar strips could increase the flexural and creep performances of the WPVC composite members both in flat-wise and edge-wise directions. The improvement in the edge-wise direction was relatively greater than that in the flat-wise direction, representing the loading direction dependence for this composite member. Abaqus finite element analysis (FEA) software was applied to predict the creep responses of WPVC composite members based on the characteristics of the individual component material; these results were then verified by the experimental results. Good correlations between FEA and experimental results were found in all cases, indicating that Abaqus software with the power law creep model can be used as an alternative tool for determining the creep responses of WPVC composites.

A Study on Mechanical Properties of Short Kenaf Fiber Reinforced Polylactide (PLA) Composites

In this study, bast fibers of kenaf (Hibiscus cannabinus L.), in the form of randomly dispersed short-fiber reinforcement, were loaded into poly(lactic acid) (PLA) or simply polylactide. Twin-bladed melt mixing followed by hot-pressing was chosen as the present composite molding with fiber weight fractions varied from 0wt% (i.e. neat PLA) to 20wt% by 5wt% increment. From the optical microscopic surface images, kenaf fibers were found to evenly be dispersed in the present composites with random fiber orientations in the two-dimensional flat-wise directions. Tensile strength and strain at break of the composites were found to decrease as compared to those of neat PLA. On the other hand, the tensile moduli both at initial and at several stress levels up to the final breakage were found to be improved via kenaf fiber loading. Two-parameter Weibull plots in terms of tensile strength and SEM fractography of the fractured surfaces were also examined and complicated and multiple sources for the fracture initiation and propagation in the present composites were implied. Finally, flexural properties, Charpy impact toughness, plain strain fracture toughness and S-N curves for the present composites were also shown and then discussed to sustain some benefits of the kenaf fiber loading.

Effects of cross‐section design and loading direction on the creep and fatigue properties of wood/PVC composite beams

AbstractThe creep and fatigue properties of two wood/poly(vinyl chloride) (WPVC) composite beams were studied under flexural and cyclic deformations. The effects of cross‐section design and load direction were the main interests. The weight ratio of the wood and PVC compound used was 1:1, and the composites were produced by using an industrial‐scale twin‐screw extruder. In creep testing, the changes in WPVC beam displacement for the edgewise and flatwise directions increased with time. The WPVC composite with a greater size (thickness) and number of cores had the higher creep resistance. Testing a WPVC composite in the flatwise direction gave less time‐dependence than testing in the edgewise direction. The recommended applied loads for optimum creep resistance of the WPVC specimens were found to be 20 and 30% of the ultimate load to failure, depending on the size and number of cores for the cross‐section used. In fatigue testing, the number of cycles to failure for both WPVC composite specimens tested in the flatwise direction was greater than that for testing in the edgewise direction. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers