Search results

Adhesive bonding is critical to the effectiveness and structural integrity of 3D printed components. The purpose of this study is to investigate the effect of joint configuration on failure loads to improve the design and performance of single lap joints (SLJs) in 3D printed parts.

In this study, adherends were fabricated using material extrusion 3D printing technology with polyethylene terephthalate glycol (PETG). A toughened methacrylate adhesive was chosen to bond the SLJs after adherend printing. In this study, response surface methodology (RSM) was used to examine the effect of the independent variables of failure load, manufacturing time and mass on the dependent variable of joint configuration; adherend thickness (3.2, 4.0, 4.8, 5.6, 6.4, and 7.2 mm) and overlap lengths (12.7, 25.4, 38.1, and 50.8 mm) of 3D printed PETG SLJs.

The strength of the joints improved significantly with the increase in overlap length and adherend thickness, although the relationship was not linear. The maximum failure load occurred with a thickness of 7.2 mm and an overlap of 50.8 mm, whilst the minimum failure load was determined with a thickness of 3.2 mm and an overlap of 12.7 mm. The RSM findings show that the optimum failure load was achieved with an adherend thickness of 3.6 mm and an overlap length of 37.9 mm for SLJ.

This study provides insight into the optimum failure load for 3D printed SLJs, reducing SLJ production time and mass, producing lightweight structures due to the nature of 3D printing, and increasing the use of these parts in load-bearing applications.

Breastfeeding bras are functional garments having specialised features to facilitate easy breastfeeding. The purpose of this paper is to design and develop breastfeeding bra prototypes with a focus on the needs of the user.

The method uses gathering breastfeeding user requirements through consumer surveys. The subsequent data analysis and a literature review provided the basis for feature selection for the breastfeeding bra designs. The bras were constructed using ultrasonic welding and bonding techniques. The mechanical properties of the fabric were measured. Lastly, the designed bras underwent a wear trial to evaluate their effectiveness.

The bra prototypes use non-restrictive designs and aesthetically appealing construction methods with smooth panel joints. The results of the wear trial demonstrated the successful incorporation of user requirements in the final product.

The insights from user-need mapping through consumer surveys and a literature review provided the basis for the new design of breastfeeding bras using stitchless technology. The developed bras have unique features that have not been explored earlier in this product category.

The purpose of this review paper is to provide a review of the most recent advances in the field of manufacturing composite sandwich panels along with their advantages and limitations. The other purpose of this paper is to familiarize the researchers with the available developments in manufacturing sandwich structures.

The most recent research articles in the field of manufacturing various composite sandwich structures were reviewed. The review process started by categorizing the available sandwich manufacturing techniques into nine main categories according to the method of production and the equipment used. The review is followed by outlining some automatic production concepts toward composite sandwich automated manufacturing. A brief summary of the sandwich manufacturing techniques is given at the end of this article, with recommendations for future work.

It has been found that several composite sandwich manufacturing techniques were proposed in the literature. The diversity of the manufacturing techniques arises from the variety of the materials as well as the configurations of the final product. Additive manufacturing techniques represent the most recent trend in composite sandwich manufacturing.

This work is valuable for all researchers in the field of composite sandwich structures to keep up with the most recent advancements in this field. Furthermore, this review paper can be considered as a guideline for researchers who are intended to perform further research on composite sandwich structures.

Herein, the authors report the effects of printing parameters, joining method, and annealing conditions on the structural performance of fusion-joined short-beam sections produced by additive manufacturing.

The authors first identified appropriate printing parameters for joining segmented short beams and then used those parameters to print and fusion-join segments with different configurations of stiffeners to form a longer section of a wing or small wind turbine blade structure.

It was found that the beams with three lateral and three base stiffening ribs give the highest flexural strength among the three beams investigated. Results on joined beams annealed at different conditions showed that annealing at 70 °C for 0.5 h yields higher performance than annealing at the same temperature for longer times. It is also found that in the case of the hot-plate-welded three-dimensional (3D)-printed structures, no annealing is needed for reaching a high strength-to-weight ratio, but annealing is helpful for maximizing the modulus-to-weight ratio. Both thermal buckling and edge wrapping were observed under annealing at 70°C for 0.5 h for 3D-printed beams comprising two lateral and four base stiffening plates.

Fusion-joining of additively manufactured segments is needed owing to the constraint in building volume of a typical commercial 3D-printer. However, study of the effect of process parameters is needed to quantify their effect on mechanical performance. This investigation has therefore identified key printing parameters and annealing conditions for fusion-joining short segments to form larger structures, from multiple 3D-printed sections, such as wind blade structures.

The aim of the research presented in this paper is to provide information on the common problems of healthy homes in the context of architectural design deficiencies. Especially because determining the status of a healthy house is particularly challenging if the design is poor.

Qualitative methods, i.e. interviews, site visits and graphic elicitation diagramming were used in two different stages of data collection. They were then analysed using thematic analysis.

The findings show that the architectural elements can have positive or negative effects on the health and safe environments. The quantity of doors and the use of transparent glass have largely contributed to the thermal transmission and increased indoor temperatures. The roof aluminium sheets and absence of vents inhibited indoor heat loss. This has led to discomfort and overuse of air-conditioning units, particularly during the COVID-19 pandemic where most households stayed/worked from home. The inappropriate height of the ceiling and roof made it challenging for maintenance purpose, reducing safety levels, which could result in physical injuries.

The concept of healthy homes is not new. Studies have been conducted in Western countries and in the field of healthcare. However, there is lack of study in built environment particularly in developing countries and inadequate inter-disciplinary and empirical research to connect the healthcare field. The pervasive and recurring design deficiencies in the construction industry remain a source of unhealthy homes, which must be addressed. Future investigations are necessary to expand the conclusions that can be drawn from this paper for health equity within the society and nation.

Stitching is the traditional method of creating seams using needles and threads. However, this is not useful for waterproof breathable garments as needle holes allow water to penetrate inside the garment, compromising its functionality. This study aims to investigate different techniques for covering the needle holes formed during stitching to achieve a seam that is waterproof, durable and functionally effective.

This study investigates different methods to cover needle holes formed during stitching with the help of seam tape, seam grip adhesive and fuser thread. The emphasis is on evaluating the seam characteristics, including seam strength, seam efficiency, puckering, bending stiffness and resistance to water penetration. Statistical analysis involves the use of the Shapiro–Wilk test, Levene statistic, one-way ANOVA and Tukey’s HSD and Tamhane post-hoc tests.

The experimental results suggest that seam tape is effective in enhancing water resistance, seam strength and seam efficiency, but it contributes to stiffness and aesthetically degrades seams due to increased puckering. Meanwhile, the use of fuser thread presents an alternative, exhibiting improved waterproof properties compared to regular stitching. It offers more flexibility and less puckering compared to seam tape.

This study contributes novel insights by shifting the focus from alternative seaming methods such as bonding and welding, to enhancing traditional stitching for waterproof seam construction. While prior research primarily explored alternatives to stitching, this study uniquely addresses the effectiveness of different techniques in covering needle holes to achieve waterproof seams. The findings provide valuable information for enhancing the functionality of stitched seams in the production of waterproof breathable garments.

This paper comprehensively addresses the influence of chopped strand mat glass fiber-reinforced polymer (GFRP) patch configurations such as geometry, dimensions, position and the number of layers of patches, whether a single or double patch is used and how well debonding the area under the patch improves the strength of the cracked aluminum plates with different crack lengths.

Single-edge cracked aluminum specimens of 150 mm in length and 50 mm in width were tested using the tensile test. The cracked aluminum specimens were then repaired using GFRP patches with various configurations. A three-dimensional (3D) finite element method (FEM) was adopted to simulate the repaired cracked aluminum plates using composite patches to obtain the stress intensity factor (SIF). The numerical modeling and validation of ABAQUS software and the contour integral method for SIF calculations provide a valuable tool for further investigation and design optimization.

The width of the GFRP patches affected the efficiency of the rehabilitated cracked aluminum plate. Increasing patch width WP from 5 mm to 15 mm increases the peak load by 9.7 and 17.5%, respectively, if compared with the specimen without the patch. The efficiency of the GFRP patch in reducing the SIF increased as the number of layers increased, i.e. the maximum load was enhanced by 5%.

This study assessed repairing metallic structures using the chopped strand mat GFRP. Furthermore, it demonstrated the superiority of rectangular patches over semicircular ones, along with the benefit of using double patches for out-of-plane bending prevention and it emphasizes the detrimental effect of defects in the bonding area between the patch and the cracked component. This underlines the importance of proper surface preparation and bonding techniques for successful repair.

In this experimental investigation, the behavior of strengthened/repaired heat-damaged one-way self-compacted concrete (SCC) slabs with opening utilizing near-surface-mounted-carbon fiber reinforced polymers (NSM-CFRP) strips was explored.

CFRP strip configurations, number of strips and inclination were all investigated in this study. For three hours, slabs were exposed to temperatures of 23°C and 500°C. Four-point load was applied to control slabs, enhanced slabs and repaired slabs.

The results indicate that exposing the slabs to high temperatures reduces their load capability. The number of strips and angle of inclination around the slab opening have a considerable impact on the performance of the strengthened and/or repaired slabs, according to the experimental results. The load capacity, toughness and ductility index of a strengthened and/or repaired slab with opening increase as the number of CFRP strips increases by 143.8–150.5%, 137.3–149.9% and 122.3–124.5%, respectively. The use of NSM strips around the opening with zero inclination showed higher load compared to the NSM strips around the opening with other angles.

It is frequently important to construct openings in the slabs for ventilation, electrical supply, and other purposes. Making openings in slabs might affect the structure’s performance since the concrete and reinforcing would be cut off. SCC is a new type of concrete mixture that can fill in all the voids in the formwork with its own weight without the help of external vibration.  As a result, it is necessary to reinforce the slab under flexure and increase the flexural strength of the SCC slab. Therefore, this work investigates the effect of using NSM-CFRP strip  on the behavior of one way SCC slabs that have been heat-damaged.

The purpose of this study is to investigate the effects of a pigment coating on the mechanical properties of fluting paper.

Two different calcium carbonate pigments were used in the preparation of the coated color, precipitated calcium carbonate (PCC) and ground calcium carbonate (GCC). Fluting paper produced by recycling waste paper was used as base paper. The effects of PCC and GCC pigments on mechanical properties were compared. Ring crush test (RCT), corrugating medium test (CMT), corrugating crush test (CCT), tensile and burst strength tests were applied to the coated papers, and the results were compared to the mechanical properties of base paper.

The tensile and burst indices of the coated papers were found to be higher than base papers about 13.9% and 6.05%, respectively. While the coating process positively affected the RCT and CCT values, it did not show a significant impact on the CMT values. GCC, one of the pigments used in coating colors, had a more effective effect on the mechanical properties of fluting papers compared to PCC.

These results suggest that coating of fluting papers has a positive effect on mechanical properties and the use of GCC as a pigment is more effective than PCC.

Polyurethane (PUR) foam parts are traditionally manufactured using metallic molds, an unsuitable approach for prototyping purposes. Thus, rapid tooling of disposable molds using fused filament fabrication (FFF) with polylactic acid (PLA) and glycol-modified polyethylene terephthalate (PETG) is proposed as an economical, simpler and faster solution compared to traditional metallic molds or three-dimensional (3D) printing with other difficult-to-print thermoplastics, which are prone to shrinkage and delamination (acrylonitrile butadiene styrene, polypropilene-PP) or high-cost due to both material and printing equipment expenses (PEEK, polyamides or polycarbonate-PC). The purpose of this study has been to evaluate the ease of release of PUR foam on these materials in combination with release agents to facilitate the mulding/demoulding process.

PETG, PLA and hardenable polylactic acid (PLA 3D870) have been evaluated as mold materials in combination with aqueous and solvent-based release agents within a full design of experiments by three consecutive molding/demolding cycles.

PLA 3D870 has shown the best demoldability. A mold expressly designed to manufacture a foam cushion has been printed and the prototyping has been successfully achieved. The demolding of the part has been easier using a solvent-based release agent, meanwhile the quality has been better when using a water-based one.

The combination of PLA 3D870 and FFF, along with solvent-free water-based release agents, presents a compelling low-cost and eco-friendly alternative to traditional metallic molds and other 3D printing thermoplastics. This innovative approach serves as a viable option for rapid tooling in PUR foam molding.