30 Oct 2025

Thermomechanical Material Characterization of Polyethylene Terephthalate Glycol Carbon Fiber 30% for Large-Format Additive Manufacturing of Polymer Structures

Abstract: Large-format additive manufacturing (LFAM) is used to print large-scale polymer structures. An understanding of the thermal and mechanical properties of polymers suitable for large-scale extrusion is needed for de-sign and production capabilities. An in-house-built LFAM printer was used to print polyethylene terephthalate glycol with 30% short carbon fiber (PETG CF30%) samples for thermomechanical characterization. Thermogravimetric analysis confirmed the samples had 30% carbon fiber by weight. X-ray microscopy and porosity studies found 25% porosity for undried material and 1.63% porosity for dry material. Differential scanning calorimetry showed a glass transition temperature (Tg) of 66°C, while dynamic mechanical analysis found Tg to be 82°C. The rheology indicated that PETG CF30% is a good printing material at 220°C–250°C. Bending experiments showed an average of 48.5 megapascals (MPa) for flexural strength, while tensile experiments found an average tensile strength of 25.0 MPa at room temperature. Comparison with the literature demonstrated that the 3D-printed PETG CF30% had a high Young’s modulus and was of similar tensile strength. For design purposes, prints from LFAM should be considered from a bead–layer–part standpoint. For testing purposes, both material choice and print parameters should be considered, especially when considering large layer heights.

15 Aug 2024

Repair Quality Assessment: Spiral 4

Abstract: The Expedient and Expeditionary Airfield Damage Repair (E-ADR), Joint Capability Technology Demonstration (JCTD) program developed, demonstrated, and transitioned a repeatable capability for rapidly repairing bomb-damaged craters at adaptive base locations using logistically friendly technologies, indigenous materials, and less manpower than traditional crater repair methods. Within the E-ADR JCTD program, quality assessment took a major role to ensure quality repairs were performed while meeting the requirements of “just enough, just in time.” Repair criteria for backfill compaction and surface cap quality were developed through extensive testing. These criteria were incorporated into an easy-to-use and deployable smartphone application, the E-ADR Repair Assessment (ERA) application. This report focuses on the backfill quality assessment criteria development, roughness tolerance of surface caps checking procedure, and the development of the ERA application. The criteria and the ERA application both proved successful in the expedient evaluation of backfill and surface cap materials.

16 Nov 2020

Magnetorheological Composite Materials (MRCMs) for Instant and Adaptable Structural Control

Abstract: Magnetic responsive materials can be used in a variety of applications. For structural applications, the ability to create tunable moduli from relatively soft materials with applied electromagnetic stimuli can be advantageous for light-weight protection. This study investigated magnetorheological composite materials involving carbonyl iron particles (CIP) embedded into two different systems. The first material system was a model cementitious system of CIP and kaolinite clay dispersed in mineral oil. The magnetorheological behaviors were investigated by using parallel plates with an attached magnetic accessory to evaluate deformations up to 1 T. The yield stress of these slurries was measured by using rotational and oscillatory experiments and was found to be controllable based on CIP loading and magnetic field strength with yield stresses ranging from 10 to 104 Pa. The second material system utilized a polystyrene-butadiene rubber solvent-cast films with CIP embedded. The flexible matrix can stiffen and become rigid when an external field is applied. For CIP loadings of 8% and 17% vol %, the storage modulus response for each loading stiffened by 22% and 74%, respectively.

1 Oct 2020

Laboratory Evaluation of Aquablok™ Erosion Resistance: Implications for Geotechnical Applications

Abstract: AquaBlok™ (AB) is a commercial product traditionally used as an alternative material for contaminated sediment capping applications. Previous studies of AB capping performance have reported enhanced stabilization through increased erosion resistance. Subsequently, AB has been considered for use as an alternative levee repair material due to its cohesive properties. Through a series of laboratory experiments, this study investigated the erosion behavior of new AquaBlok formulations (10%, 20%, and 30% clay by weight) under increased shear stresses previously unachievable in the previous tests. The new AquaBlok formulations were tested in non-compacted and compacted states to simulate the physical properties in capping and levee repair applications. In the non-compacted state, excess hydration of the clay matrix extended approximately 5 cm below the bed surface, which greatly reduced erosion resistance and was independent of clay percentage. Below this horizon, critical shear stress increased, and erosion rates decreased, with clay percentage, respectively. However, this does not consider a continuous change in hydration state when exposed to free water. In the compacted state, erosion rates were greatly arrested, with measureable erosion only possible under the maximum applied shear stress (24 Pa). The results are discussed in the context of capping and levee applications.