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Continuous fiber reinforced thermoplastics (CFRTPs) are valued for their high strength-to-weight ratios, corrosion resistance, and recyclability over traditional structural materials. However, CFRTPs are difficult to fabricate compared to thermoset composites, a significant barrier to their adoption in construction and infrastructure. The University of Maine's Advanced Structures and Composites Center has developed several innovative manufacturing and post-processing techniques to address fabrication challenges. The Continuous Forming Machine (CFM) is a processing device for non-reactive thermoplastic pultrusion, efficiently producing structural profiles like rods, plates, and channels. The CFM platform can be expanded with co-processes to create parts such as field-bendable concrete reinforcing bar. Further, effective post-forming processes will be crucial for adapting CFRTP components to on-site infrastructure applications. Localized thermoforming targets specific bending regions within a CFRTP component, offering a field-friendly approach over stamp thermoforming. Using localized heating methods, such as embedded heating elements, CFRTP panels can be locally thermoformed into three-dimensional components. Additional work has been performed to mitigate wrinkle formation in the bending of thick-gauge CFRTP laminates by implementing modifications to component architecture. This research presents significant advancements towards the widespread adoption of CFRTPs for infrastructure, demonstrating the technology's adaptability for onsite manufacturing and its future impact on sustainable construction practices. [ABSTRACT FROM AUTHOR]

Recently, 3D printing of large, structural polymer parts has received increasing interest, especially for the creation of recyclable structural parts and tooling. However, the complexity of large-scale 3D polymeric printing often dictates resource-intensive trial and error processes to achieve acceptable parts. Existing computational models used to assess the impact of fabrication conditions typically treat the 3D-printed part as a continuum, incorporate oversimplified boundary conditions and take hours to days to run, making design space exploration infeasible. The purpose of this study is to create a structural model that is computationally efficient compared with traditional continuum models yet retains sufficient accuracy to enable exploration of the design space and prediction of part residual stresses and deformations. To this end, a beam-based finite element methodology was created where beads are represented as beams, vertical springs represent inter-bead transverse force transfer and multi-point, linear constraints enforce strain compatibility between adjacent beads. To test this framework, the fabrication of a large Polyethylene terephthalate glycol (PETG) wall was simulated. The PETG was modeled as linearly elastic with an experimentally derived temperature-dependent coefficient of thermal expansion and elastic modulus using temperature history imported from an ABAQUS thermal model. The results of the simulation were compared to those from a continuum model with an identical material definition, showing reasonable agreement of stresses and displacements. Further, the beam-based model required an order of magnitude less run time. Subsequently, the beam-based model was extended to allow separation of the part from the printing bed and the inclusion of part self-weight during fabrication to assess the significance of these effects that pose challenges for existing continuum models. [ABSTRACT FROM AUTHOR]

A method is proposed to locally heat areas of thick (>25.4 mm) continuous glass fiber reinforced thermoplastic (C-FRTP) composites with embedded wire mesh resistive heating elements. Four test specimens including 10.6 cm wide nichrome mesh heating elements embedded in C-FRTP laminates were fabricated and used for heating trials, showing that the composite can be locally heated to near the thermoplastic forming temperature over its entire thickness in less than 1 hour. The heating trials were simulated using a purpose-built finite difference model to investigate detailed temperature distributions. The simulations show that the internal resistive heating elements are capable of locally increasing the temperature of the composite with negligible effect on the adjacent material. Heating efficiency is between 73% and 77%, with temperature differences in the z -direction at peak temperatures less than 35°C. Temperature uniformity can be improved by longer heating times and more heating elements. The local heating method does not cause deconsolidation of the part. The heating method was also experimentally assessed on a more complex cross-section laminate with varying thickness and a foam core using stainless steel mesh heating elements. Results from the first heating tests were applied to the experimental assessment of the more complex laminate to reduce z -direction temperature differences. Numerical simulation of the heating of the foam core laminate showed a z -direction temperature range of 15.5°C. The results of this study show that embedded resistive heating is a cost-effective and simple method for heating a local portion of a thick fiber reinforced thermoplastic composite. [ABSTRACT FROM AUTHOR]

This paper describes the structural performance of an innovative wood plastic composite (WPC) sheet piling. Tensile coupon tests were performed to determine tensile strength and modulus over a range of strain rates for both WPC and specimens cut from commercially available vinyl sheet piles. Full scale four-point bending tests were conducted up to failure on 20 sets of joined pairs of WPC Z-piles with four different span lengths. For comparison, bending and coupon-level tension tests were also conducted on commercially available vinyl Z-piles and coupons cut from them. The coupon-level tests indicated that WPC had on average a 14% greater modulus than the vinyl specimens in the initial linear range, defined as between 10 and 40% of the respective material's ultimate tensile strength. However, if the modulus is computed over the same stress range of 10-40% of the WPC ultimate tensile strength, both materials have a similar modulus. The vinyl had a tensile strength 3.6 times that of the WPC. During the bending tests, the hollow cross section WPC Z-piles failed primarily in bending-induced tension, while the solid vinyl Z-piles exhibited buckling of the compression flange. Creep rupture testing was conducted for pair of WPC Z-piles in a four-point bending setup to determine long-term load- carrying capacity. No loss of load-carrying capacity was observed during the 90-day test and creep rates generally decreased during the test. However, creep deflections were larger than what would normally be exhibited by wood structural members. While additional studies are needed to address the effects of water absorption on WPC properties, the findings show promise for wood plastic composite light duty sheet piling retaining wall structures. DOI: 10.1061/(ASCE)MT.1943-5533.0000132 CE Database subject headings: Composite materials; Composite structures; Sheet piles; Stiffness; Creep. Author keywords: Composite materials; Composite structures; Sheet piles; Stiffness; Creep.

This study focuses on the in-plane load-deflection and buckling response of pressurized fabric arches of constant circular cross section. These lightweight portable structural members support tents used for temporary medical facilities, disaster- relief shelters, and military applications. A quadratic Timoshenko beam element is developed for materially and geometrically nonlinear analysis based on a virtual work principle that includes work done by internal pressure due to deformation-induced volume changes. The inability of the arch fabric to carry compressive stress is addressed with a nonlinear moment-curvature relationship that captures the effect of fabric tensile stiffness, internal pressure, and axial load. A corotational formulation and cylindrical arc-length solver are used to permit large displacement analysis and the tracking of postbuckling softening response. A convergence study demonstrates the good performance of the element and the solver. Results of laboratory load tests on a 9.5 m-span semicircular inflated fabric arch are presented, and shown to agree well with the model predictions. Parametric studies are conducted to examine the significance of inflation pressure and lateral restraint on arch deflections and buckling under the action of code-specified snow loads. The numerical studies show that the work done by the confined air significantly increases arch load capacity, and that shear deformations of woven fabrics can significantly reduce arch capacity. DOI: 10.1061/(ASCE)ST.1943-541X.0000068 CE Database subject headings: Arches; Finite element method: Buckling; Load factors; Deflection; Stability; Cross sections.

Lightweight, portable air-pressurized beams and arches serve as primary load-carrying members for a number of civilian and military structures. These members are made from synthetic fibers that are woven or braided into a circular cross section. The pressurized air provides structural capacity by pretensioning the fabric and through its behavior as a confined gas. In this paper, a beam finite element is developed for the analysis of pressurized fabric beams based on virtual work principles. Work done by internal pressure due to deformation-induced volume changes is included in the formulation. A nonlinear moment-curvature relationship accounts for fabric wrinkling, and shear deformations are incorporated. A mixed-interpolation Timoshenko beam element is used to discretize the virtual work expression. A numerical method for determining the moment-curvature relationship of an inflated beam made from a fabric obeying a nonlinear stress-strain relationship is developed. Results of experiments on pressurized fabric beams loaded in three- and four-point bending are presented, and the finite-element model is shown to accurately predict experimentally observed load-deflection response for a range of pressures. Simulations demonstrate that in addition to prestressing the fabric, the pressurized air significantly increases beam capacity as the beam volume decreases due to deformation. DOI 10. 1061/(ASCE)0733-9445(2007) 133:7(990) CE Database subject headings: Beams; Finite element method; Fabrics; Tubes; Deformation.

This study addresses the development and structural testing of a hybrid sheathing panel designed to improve the lateral resistance of light wood-frame shear walls. The panel consists of thin outer sheets of oriented-strand board (OSB) bonded to strips of fiber-reinforced polymer (FRP) that are sandwiched between the OSB panels at the edges. The FRP-reinforced panel material selection and fabrication are summarized. Monotonic and cyclic tests were conducted to assess the performance of single-connector sheathing-to-framing connections using both OSB and FRP-reinforced OSB. Twenty-four full-scale shear walls were tested under monotonic and cyclic racking loads to determine the benefits of FRP-reinforced OSB to wall lateral load resistance. For a 102 mm perimeter nail spacing, FRP-reinforced OSB-sheathed walls exhibited increases in peak capacity and energy dissipation under cyclic loading of 27 and 73%, respectively, compared to walls sheathed with conventional OSB. Based on these experimental results, FRP-reinforced OSB panels appear to have significant potential for increasing the energy dissipation capacity and lateral load resistance of wood-frame structures subjected to extreme lateral loads. However, their full utilization will require higher strengths for critical shear wall components such as tension ties and framing interconnections, as well as improvements in sheathing-to-framing fastener performance. DOI: 10.1061/(ASCE)0733-9445(2006)132:1(153) CE Database subject headings: Timber construction; Fiber reinforced polymers; Shear walls; Seismic design; Panels; Wooden structures.

his paper examines the effect of dowel looseness on the structural response of jointed concrete pavements. A technique for modeling dowels in 3D finite-element analyses of rigid pavement systems is presented that relies on an embedded formulation of a quadratic beam element. This embedded element permits the efficient modeling of dowel looseness using a nodal contact approach and allows the dowels to be exactly located irrespective of the slab mesh lines. The embedded bending element is extended to include a general bond-slip law, and the practical case of a Winkler foundation sandwiched between the dowel and slab is implemented. The results of parametric studies examining the significance of dowel looseness on the response of rigid jointed pavements to both axle and combined axle and thermal loadings are presented. These studies indicate that significant increases in both slab and soil stresses can be expected due to small gaps (

The development and implementation of a general, three-dimensional (3D) embedded bending member suitable for modeling dowel action is presented. The development is motivated by the desire to efficiently model rigid concrete pavement slabs with doweled joints using solid brick elements without requiring the mesh nodes to coincide with the dowel element nodes. All derivations are done with respect to an arbitrarily oriented coordinate system. The stiffness matrix of the embedded dowel element is expressed as a transformation of the unembedded dowel element stiffness matrix, eliminating the need for special integration techniques. Consideration is given to axial debonding of the dowel, as well as the nonlinear case where a gap exists between the dowel and surrounding material. Details of the object-oriented implementation of the element and its incorporation in a general, nonlinear solution strategy are presented. Convergence and parametric studies were performed using a realistic model of two rigid, concrete pavement slabs subjected to static axle loading near the joint. The results of these studies demonstrate the applicability of the element as well as indicating the potential for significant detrimental effects on doweled joint performance when gaps exist between the dowels and the pavements slabs.

This study focuses on the development and implementation of a layered analysis method for predicting the response of FRP-reinforced glulam beams with partially composite concrete decks. The development of the model is quite general, allowing the easy incorporation of material nonlinearity and nonlinear load-slip response of wood-concrete connectors. An effective numerical algorithm is developed and implemented for solving the governing integral and differential equations, which relies on Newton's method and a single level of iteration. The model is verified through comparison with published experimental data on the bending response of partially composite wood-concrete beams.