Guoqiang Li

Louisiana State University | LSU · Department of Mechanical and Industrial Engineering

Vitrimers with self‐healing, recycling, and remolding capabilities are changing the paradigm for thermoset polymer design. In the past several years, vitrimers that exhibit shape memory effects and are curable by ultraviolet (UV) light have made significant progress in the realm of 4D printing. Herein, we report a molecular dynamics (MD) modeling f...

This study investigates a neoteric approach in manufacturing lunar regolith-filled shape memory vitrimer (SMV) composites for extraterrestrial applications. A SMV with robust mechanical properties was combined with locally available lunar regolith to form a composite material. Fourier Transfer Infrared Spectroscopy (FTIR), Scanning Electron Microsc...

Proposing shape memory polymer (SMP) materials for lifting and rigging equipment can foster unparalleled advancements and several potential applications in various industries. This pioneering study focuses on the thermomechanical properties of SMP wire ropes and their components during programming steps for small- and finite-sliding contact deforma...

Herein, we report a new solar energy harvesting approach by connecting two form-stable phase change materials under moist environment dissolved with carbon dioxide (CO2). Recently, a smart and creative energy harvesting concept has emerged by using form-stable phase change material (PCM) composites without any thermoelectric device. In that approac...

Over the years, thermoelectric energy harvesting has been becoming a topic of intensive research and thermo-electric power generator has been utilized in various energy harvesting applications. However, a thermoelectric device is required to harvest energy, which has relatively low efficiency and high cost. To overcome such a common problem, the ob...

A method for detecting low-velocity impact damage in carbon fiber reinforced polymer (CFRP) is presented. It involves the use of the Impulse Excitation Technique (IET) and hysteresis loops to calculate the damping parameter of T700/NCT304-1 carbon/epoxy samples subjected to various low-velocity impact energies. The value of the coefficient of resti...

Lightweight materials are highly desired in many engineering applications. A popular approach to obtain lightweight polymers is to prepare polymeric syntactic foams by dispersing hollow particles, such as hollow glass microbubbles (HGMs), in a polymer matrix. Integrating shape memory vitrimers (SMVs) in fabricating these syntactic foams enhances th...

The utilization of multifunctional composite materials presents significant advantages in terms of system efficiency, cost-effectiveness, and miniaturization, making them highly valuable for a wide range of industrial applications. One approach to harness the multifunctionality of carbon fiber reinforced polymer (CFRP) is to integrate it with a sec...

Highlights: • Natural and synthetic fibers hybrid composite were designed, fabricated, and tested. • A newly designed shape memory vitrimer made the hybrid composites multifunctional. • Hybridization improves mechanical properties 5-fold higher than coir fiber alone. • Hybrid sample shows repeated room temp. damage healing with excellent shape memo...

Abstract Natural fibers have high potential as renewable reinforcement for polymers; however, their lower load-carrying capacity compared to synthetic fibers significantly limits the wide application in fiber-reinforced polymer composites. In laminated composite beams under bending load, the normal stress is the highest on the top and bottom layers...

Abstract Cultivated natural fibers have a huge possibility for green and sustainable reinforcement for polymers, but their limited load-bearing ability and flammability prevent them from wide applications in composites. According to the beam theory, normal stress is the maximum at the outermost layers but zero at the mid-plane under bending (with (...

Herein, a new lightweight syntactic foam is reported with strong mechanical properties, unique multifunctionalities, and recyclability. Multifunctionality of materials and structures has gained ever‐increasing interest as an excellent approach to designing minimalistic systems. Inspired by nature, these materials can perform multiple functions besi...

While injection molding is becoming the fabrication modality of choice for high-scale production of microfluidic devices, especially those used for in vitro diagnostics, its translation into the growing area of nanofluidics (structures with at least one dimension <100 nm) has not been well established. Another prevailing issue with injection moldin...

Shape memory vitrimers (SMVs) are an emerging class of advanced materials that have garnered significant interest from researchers in the past five to six years. These materials can return to their original shape when exposed to a stimulus, while also healing damage they have sustained. However, achieving both high healing/recycling efficiency and...

Cultivated natural fibers have a huge possibility for green and sustainable reinforcement for polymers, but their limited load-bearing ability and flammability prevent them from wide applications in composites. According to the beam theory, normal stress is the maximum at the outermost layers but zero at the mid-plane under bending (with (non)linea...

Natural fibers have a lot of potentials as renewable reinforcements for polymers. However, their lower load-carrying capacity compared with synthetic fibers made it a challenge to use them as polymer reinforcements. When a laminated composite beam is bent, the normal stress is the highest on the top and bottom layers and zero in the midplane due to...

Herein, we present a new sandwich panel composed of a carbon fiber grid-stiffened shape memory vitrimer (SMV) core. The sandwich panels were fabricated via a pin-guided dry-weaving technology, and their impact responses were evaluated via low-velocity impact testing. The main failure mode observed after the first round of impact was the transverse...

Improving the fireproof performance of polymers is crucial for ensuring human safety and enabling future space colonization. However, the complexity of the mechanisms for flame retardant and the need for customized material design pose significant challenges. To address these issues, we propose a machine learning (ML) framework based on substructur...

Damage healing in fiber reinforced thermoset polymer composites has been generally divided into intrinsic healing by the polymer itself and extrinsic healing by incorporation of external healing agent. In this study, we propose to use a hybrid extrinsic-intrinsic self-healing strategy to heal delamination in laminated composite induced by low veloc...

The lamination of strong synthetic fibers, such as carbon and glass, greatly enhances the load carrying capacity of lightweight polymer composites. Such fiber-reinforced polymer (FRP) composites face a significant challenge of delamination due to the various load applications during practical use. Especially the functional properties, such as self-...

Natural fibers have high potential as renewable reinforcement for polymers; however, their lower load-carrying capacity compared to synthetic fibers significantly limits the wide application in fiber-reinforced polymer composites. In laminated composite beams under bending load, the normal stress is the highest on the top and bottom layers but is z...

In the recent decades, with rapid development in computing power and algorithms, machine learning (ML) has exhibited its enormous potential in new polymer discovery. Herein, the history of ML is described and the basic process of ML accelerated polymer discovery is summarized. Next, the four steps in this process are reviewed, that is, dataset sele...

Herein, we report the first hybrid open-cell foam with revisable actuation. Open-cell foams with revisable actuation are favoable for many applications. However, it is challenging to fabricate such open-cell foams with very low density. This study presents a novel concept of creating hybrid two-way (2W) shape memory open-cell foams using two-way sh...

Two-way shape memory polymers with reversible elongation upon cooling (EUC) and contraction upon heating (CUH) have emerged as promising smart materials for use in soft actuators. However, it remains challenging to develop organogels with as high as possible actuation strain. Here, novel photo-crosslinkable poly(1,4-butadiene) (PBD) based organogel...

Inorganic fillers have been used to improve the out-of-plane mechanical properties of carbon fiber reinforced polymer (CFRP) composite laminates for decades. Nonetheless, its associated high cost and environmental unfriendliness is a concern. Biomaterials are currently being explored as fillers in polymeric materials due to their low cost, wide ava...

Thermomechanical constitutive modeling is essential for shape memory polymers (SMPs) to be used in engineering structures and devices. However, the classical method of deriving constitutive models is difficult, time consuming, and relies heavily on trial and error. In this work, we aim to decrease the time and resources needed to develop new thermo...

The problem of loss circulation in geothermal wells is inherently challenging due to high temperatures, brittle rocks, and presence of abundant fractures. Because of the inherent challenges in geothermal environments, there are limitations in selecting proper lost circulation materials (LCMs). Traditional LCMs such as calcium carbonates that are co...

Geothermal drilling is highly affected by mud losses. This adverse event is the leading cause of non-productive time in geothermal well construction. Mud losses account for 20% of total drilling costs in geothermal drilling. If not adequately addressed, mud losses can lead to costly drilling problems such as stuck pipe, kicks, and well control even...

Cyclic topologies or loops in crosslinked networks have negative effect on mechanical and functional properties. In this study, an epoxy resin diglycidyl ether of bisphenol A (DGEBA) crosslinked by a hardener 4,4-diaminodiphenyl methane (DDM) with various cyclic topologies were simulated to find correlations between the mechanical/shape memory prop...

Shape memory polymers (SMPs) are a new member of the smart materials family. SMPs have found wide applications or potential applications in almost all manmade structures and devices. In order to better design smart structures and devices using SMPs, thermomechanical constitutive modeling is essential. In this insight paper, we will focus on present...

In this paper, an open-cell metallic foam was filled in by a tough shape memory polymer (SMP), to form a hybrid metal/polymer composite with multifunctionalities and enhanced mechanical properties. This work aims to study the positive composite actions between the metallic skeleton and the SMP filler. Mechanical, thermal, and conductive properties...

Laminated multifunctional composites are highly desired in modern lightweight engineering structures. The purpose of this study is to develop a composite laminate with impact tolerance, delamination healing, strain sensing, Joule heating, deicing, and room temperature shape restoration functionalities. In this study, a novel self-healable and recyc...

Lost circulation is a severe problem encountered while drilling operations. Huge resources, efforts, and time are spent treating fluid losses worldwide. Treatment methods vary depending on the loss amount and severity, such as using conventional lost circulation material (LCM), smart LCMs, LCM pills, cement, and advanced drilling operations. Howeve...

Novel UV curable acrylic pressure-sensitive adhesives (PSAs) with exceptional flame retardancy and promising two-way shape memory effect have been developed using a commercial diethyl phosphoramidate as multifunctional tackifier for the first time. The abundant hydrogen bonds and high viscosity of the resultant networks contribute to the low temper...

Shape memory polymers (SMPs) are one of the intriguing functional materials and have been widely and intensively studied. In order to apply these new polymers to load bearing engineering structures and devices, developing physics-based thermomechanical constitutive models is mandatory. The aim of this Tutorial is to demonstrate how to establish a t...

Novel syntactic foams were prepared by incorporating three types of glass microbubbles in a crosslinked cis poly(1,4-butadiene) (cPBD) matrix. The as-prepared semi-crystalline polymer-based syntactic foams displayed a clear two-way shape memory effect (2W-SME) with remarkable strain actuation of about 56% expansion when the temperature drops from 6...

Here we report a thermoset shape memory polymer-based syntactic foam inherently integrated with flame retardancy, good mechanical properties, excellent shape memory effect, and 3D printability. The syntactic foam is fabricated by incorporating a high-temperature shape memory polymer (HTSMP) as the matrix, with 40 vol % hollow glass microspheres (HG...

Shape memory polymers (SMP) have been a field of interest for researchers over the past few decades and SMPs with unique characteristics are being developed continuously. Careful, time-consuming design is required for improved materials. Polymer informatics is part of an effort to shorten the development time of polymers by using computation and da...

Artificial muscle is an emerging material in the field of smart materials with application in aerospace, robotic, and biomedical industries. Recently, innovative actuation devices based on artificial muscles with performances surpassing those of natural muscles in many aspects have been developed. However, most of the artificial muscles are facing...

Polymeric artificial muscles, which mimic the function of human muscles, have found wide-spread applications in soft robot, actuator, gripper, and smart textile. A recent development is that conventional polymeric fibers with negative coefficient of thermal expansion (NCTE), such as Nylon fiber and Polyethylene fiber, can demonstrate torsional actu...

Although laminated composites are characterized as having high specific strength, stiffness, corrosion resistance, and have been widely used in load bearing structures, they are vulnerable to low velocity impact damage. Under a low velocity impact, various types of damages such as delamination, matrix cracking, fiber/matrix interfacial debonding, a...

In the past several decades, cohesive zone models (CZMs) have been widely utilized for understanding fracture of adhesively bonded structures including adhesively bonded joints due to its fairly simple and accurate predictive ability. In CZMs the nonlinear interfacial fracture behaviors are described by the traction-separation laws (also referred t...

To meet increasingly complex needs in modern industries, it is highly desired to develop thermoset polymers with multifunctional properties. For example, in electrical and electronic fields, fire hazard caused by the flammability of thermoset polymers always leads to a great loss of lives and properties. To save energy and time, rapid prototyping o...

This chapter discusses the healing efficiency characterization of self-healing polymers. Both qualitative and quantitative characterizations are discussed. Qualitative evaluation such as direct observation of healing and FTIR characterization of chemical bond reformation is presented in detail. Quantitative characterization and calculation of heali...

In this chapter, we first reviewed the various crack self-healing strategies. We then focused on self-healing of thermosetting shape memory polymer (SMP) composite according to the close-then-heal (CTH) healing strategy. Three types of composite structures were prepared, including thermosetting SMP-based syntactic foam cored sandwich, grid stiffene...

In this chapter, various self-healing composites per the close-then-heal strategy were studied. Two types of stimuli-responsive fibers were used as the crack closing device or suture: one is tension programmed shape memory polymer fiber, and the other is pre-stretched polymeric artificial muscle that is fabricated by twisting and coiling of precurs...

The last several decades have witnessed remarkable advances in smart materials, which will be playing a significant role in the areas of aerospace structures, transportation vehicles, maritime and offshore structures, wind turbine blades, pipelines, pressure vessels, civil engineering structures, medical devices and implants, household products, sp...

Self-healing smart materials have been studied extensively during past decades. The recent developments in self-healing materials have resulted in a new generation of load-carrying smart material systems with the ability to heal micro-scale to structural-scale damages. The self-healing agent might contribute to the load-carrying capability of the s...

Cellular materials have been widely used in load carrying lightweight structures. Although lightweight increases natural frequency, low stiffness of cellular structures reduces natural frequency. Designing structures with higher natural frequency can usually avoid resonance. In addition, because of the less amount of materials used in cellular stru...

Additive Manufacturing (AM) is a crucial component of the smart manufacturing industry. In this paper, we propose an automated quality grading system for the fused deposition modeling (FDM) process as one of the major AM processes using a developed real-time deep convolutional neural network (CNN) model. The CNN model is trained offline using the i...

This study proposes an approach to produce a jammed architectural structure without human intervention to clog remote fractures with large widths. Granular particles, slender members, and two-dimensional elements are fabricated and programmed to build a self-assembled three-dimensional architecture. Shape and surface properties of individual compon...

The concept of superhydrophobicity has been widely used after years of theoretical and experimental exploration. Researchers have obtained materials with excellent surface superhydrophobicity for numerous areas (e.g. textiles, paints, and coatings industries), through different design and synthesis methods using low surface energy components (LSECs...

The advocacy of carbon neutrality and circular economy encourages people to pursue self-healing and recycling of glassy thermoset polymers in a more realistic and energy-saving manner, the best being intrinsic healing under room temperature. However, the high mechanical robustness and healing ability are mutually exclusive because of their complete...

Herein, a solvent-based green recycling procedure is reported for recycling thermoset epoxy resins (TERs) and carbon fiber reinforced epoxy composites (CFRECs) employing ionic liquids (ILs) and alcohols under mild conditions. With melting points less than 100 °C, ILs are defined as organic salts, typically composed of bulky cations with organic or...

Lost circulation presents challenging issues in drilling operations, especially in high-temperature and fractured formations. Lost circulation events increase the nonproductive time (NPT) and the total cost of drilling operations. In some severe cases of high or total losses, well control is jeopardized, leading to a loss in lives and resources. Th...

Herein new lattice unit cells with buckling load 261–308% higher than the classical octet unit cell were reported. Lattice structures have been widely used in sandwich structures as lightweight core. While stretching dominated and bending dominated cells such as octahedron, tetrahedron and octet have been designed for lightweight structures, it is...

In this study, two general solutions for the dynamic tensile load-carrying capacity of brittle materials subject to an arbitrary incident stress wave in the form of Fourier integral are derived. In order to verify the general solutions, we reduce them to three particular solutions, respectively, i.e., trapezoidal pulse, quadratic pulse and cubic pu...

This paper studies the rheology and annular flow of a smart lost circulation material (LCM) at 160 °C, using a high-temperature flow loop. The smart LCM is a shape memory polymer (SMP) that activates at high temperatures, and its particle size increases to seal fractures in geothermal formations. SMP was mixed with the base fluid in two different c...

In polymer composites, constrained shape recovery, either by shape memory polymer (SMP) matrix or embedded SMP fibers, is utilized to close wide-opened cracks, followed by molecular scale healing either extrinsically or intrinsically, the so-called close-then-heal strategy. The most popular means to trigger shape recovery and healing is by heating....

Here we report an intrinsically flame-retardant high-temperature shape memory photopolymer (HTSMP) with ultrahigh glass transition temperature (Tg) of 280°C and record-breaking recovery stress of 35.3 MPa. Photopolymers have been widely used in 3D printing structures with high resolution by technologies such as digital light processing (DLP). Howev...

While there have been various lost circulation materials (LCMs) available in the market for treating fractures during the drilling of oil and gas wells, there is still a demand for a technology to seal large fractures. Considering limitations on the size of the particles that can be circulated through the drilling equipment, especially the bottomho...

Structure scouting and design optimization for superior mechanical performance through inverse machine learning is an emerging area of interest. Inverse machine learning can be a substantial approach in structural design to explore complex and massive numbers of geometrical patterns within short periods of time. Here, an inverse design framework us...

Geothermal formations often contain extensive fracture networks. These fracture networks contribute to the significant loss of drilling fluids during geothermal drilling. Multiple loss circulation materials (LCM) such as fiber, granules, and pills have been proposed to tackle this problem but with only limited success. Recent advances in materials...

Lost circulation continues to be one of the most troublesome problems encountered during drilling. The financial cost of lost circulation in geothermal drilling can rise to 15% of the total drilling cost. The non-productive time from dealing with lost circulation is also costly and increases the drilling projects' duration. If not adequately addres...

Pavement, as an important transportation infrastructure, plays an essential role in modern society. Joints and cracks, which are either designed for or created by internal and external means, must be filled in with proper sealant to stop penetration of water into the surface layer and layers beneath; otherwise, they usually lead to severer prematur...

Herein, we introduce a new catalyst-free β-hydroxy phosphate ester exchange chemistry in fabricating mechanically robust vitrimer with excellent recyclability and intrinsic fire safety. The desire to use polymers sustainably and safely has driven rapid development of recyclable thermosets and flame-retardant thermosets, respectively. However, few e...

Molecular dynamics simulations were carried out to understand the mechanical and energy storage properties of bisphenyl-A diglycidyl ether cured with isophorone diamine — a thermoset shape memory polymer (TSMP) with both excellent shape memory and stress memory properties. Different cross-linked systems were created to determine which cross-linking...

Geothermal formations are naturally fractured with large fracture openings and networks. This can often lead to frequent drilling fluid loss events which is a major contributor to the cost and non-productive time in geothermal drilling. Development of smarter technologies and methods to tackle problem lost circulation is vital for geothermal drilli...

4D printing is an emerging manufacturing technology that combines complex geometries and shape memory materials together, which is important for the development of next-generation smart structures. To meet the sustainability requirement, multifunctional smart structures that can be used repeatedly for various engineering structural or construction...

Nowadays, with the advancement in modern technology, applications of polymers become wider and deeper from high tech to everyday life. Polymer composites were developed to meet increasingly high-performance demands. However, in practical applications, the complex service environments and requirements for cost-saving drive the rapid development of m...

In this article, we report that, machine learning, an artificial intelligent technique, is used to optimize biomimetic rods and lattice structures. Various structures available in nature such as plant stems and roots that exhibit better buckling resistance are mimicked and modeled using finite element analysis, to obtain a training dataset. For val...

Shape memory polymer (SMP) is a branch of polymeric smart material that possesses excellent programmable thermomechanical properties. In order to design and develop new SMP materials, it is essential to understand their constitutive behaviors. In this chapter, we summarize four main types of thermomechanical constitutive models for SMPs, i.e., rheo...

Multiscale modeling framework of polymeric artificial muscle fabricated through twisting and coiling of precursor polymeric fibers are discussed in this article. The activation mechanism in the precursor polymeric fibers is either through negative coefficient of thermal expansion such as fishing lines or sewing threads, or two-way shape memory effe...

With rapid advances in computational power, machine learning (ML) has boomed as an effective tool to discover new materials. In the field of polymers, ML has also found its applications in finding new materials with desired performance in a lot of studies. In this article, we review a brief history for ML development and summarize a main framework...

In this article, laminated composite with the ability to heal low velocity impact induced delamination designed, fabricated, and tested. The self-healable and recyclable composite is made of a self-healable and recyclable vitrimer-based shape memory polymer (VSMP) as the matrix, unidirectional Saertex glass fiber as the reinforcement, and tension p...

In this article, 3D woven fabric reinforced polymer composites are presented. We focused on 3D woven fabric reinforced shape memory polymer based syntactic foam with extrinsic self-healing capability so that low velocity impact induced damage can be healed repeatedly. To this end, we first present the mechanics of low velocity impact response, ener...