A numerical study on the influence of strain rate in finite-discrete element simulation of the perforation behaviour of woven composites

Predicting the perforation limit of composite laminates is an important design aspect and is a complex task due to the multi-mode failure mechanism and complex material constitutive behaviour required. This requires high-fidelity numerical models for a better understanding of the physics of the perforation event. This work presents a numerical study on the perforation behaviour of a satin-weave S2-glass/epoxy composite subjected to low-velocity impact. A novel strain-rate-dependent finite-discrete element model (FDEM) is presented and validated by comparison with experimental data for impacts at several energies higher and lower than their perforation limit. The strain rate sensitivity was included in the model by developing a novel user-defined material model, which had a rate-dependent bilinear traction separation cohesive behaviour, implemented using a VUSDFLD subroutine in Abaqus/Explicit. The capability of the model in predicting the perforation limit of the composite was investigated by developing rate-sensitive and insensitive models. The results showed that taking the strain rate into account leads to more accurate predictions of the perforation limit and damage morphology of the laminate subjected to impacts at different energies. The experimental penetration threshold of 89 J was estimated as 79 J by the strain-rate-sensitive models, which was more accurate compared to 52 J predicted by the strain-rate-insensitive model. Additionally, the coupling between interlaminar and intralaminar failure modes in the models led to a more accurate prediction of the delamination area when considering the rate sensitivity

Experimental and numerical study of the influence of pre-existing impact damage on the low-velocity impact response of CFRP panels

This paper presents an experimental and numerical investigation on the influence of preexisting impact damage on the low-velocity impact response of Carbon Fiber Reinforced Polymer (CFRP). A continuum damage mechanics-based material model was developed by defining a userdefined material model in Abaqus/Explicit. The model employed the action plane strength of Puck for the damage initiation criterion together with a strain-based progressive damage model. Initial finite element simulations at the single-element level demonstrated the validity and capability of the damage model. More complex models were used to simulate tensile specimens, coupon specimens, and skin panels subjected to low-velocity impacts, being validated against experimental data at each stage. The effect of non-central impact location showed higher impact peak forces and bigger damage areas for impacts closer to panel boundaries. The presence of pre-existing damage close to the impact region leading to interfering delamination areas produced severe changes in the mechanical response, lowering the impact resistance on the panel for the second impact, while for noninterfering impacts, the results of the second impact were similar to the impact of a pristine specimen

Significance of intermodal freight modal choice criteria: MCDM-based decision support models and SP-based modal shift policies

This paper reviews modal choice decisions associated with intermodal freight transportation through decision support models based on the Multi-Criteria Decision-making (MCDM) techniques and modal shift policy as�sessments based on the Stated Preferences (SP) experiments. The objectives were to determine the relevant decision criteria and their relative significance, to define methods in use, and to identify respective policies that boost intermodality. Google Scholar database and manual search using identified keywords were conducted and references of the relevant articles were double-checked. Consequently, a total of 27 articles consisting of respective 18 and 9 MCDM-based and SP-based articles were reviewed in this study. The results showed that the most commonly used decision criteria were cost, CO2 emissions, delivery time, safety, reliability, flexibility, and frequency. The cost factor was assigned the highest weight in 22 articles (or 81.4%). Analytical Hierarchy Process (AHP) technique was implemented in 12 out of 18 MCDM articles (or 66.6%)). Successful application of MCDM methods (both single and integrated) showed the suitability of these methods for intermodal freight modal choice decision-making. The results of SP experiments revealed that cost reduction policies are more effective than policies addressing other factors to increase the demand for intermodal transportation

A Review of Strategies to Prevent On-Site Construction Waste

One of the most important concerns that improves building profitability is the implementation of a positive approach to minimize construction waste. This paper will discuss the roots of construction waste, current waste reduction strategies, and lastly the possible use of waste management. Furthermore, the key environmental priority for this issue should be to control and mitigate construction waste generation. The purpose of this study is to provide prevention measures, and the rising tide of public awareness is all conspiring to modify the face of waste management. Clients, contractors, suppliers, and designers Architects & Engineers all have opportunities and duties to reduce construction waste. The outcomes of this study will assist academics in furthering their research into important management strategies for reducing on-site building waste

Life cycle assessment of brick and timber house and effects on climate change in Malaysia

Environment education is an important issue not only from the origination stage but also from the value of sustain it for now and for next generations. From the 1990s, the importance of environment conserve becomes understood for conservation effort in many areas. Among all activity, building construction industry played the principal roles in improving the environment, therefore attempt to mitigate effects from building constructions to environment. Sustainable development needs a method to evaluate and compare the environmental effect of human activity on any economic for various products. Environmental impacts include emission into the environment and utilization of resources as well as other inventions such as land use to build new products. The materials consist of brick and timber house with different roof materials. This study review the extraction of raw materials until the erected of building on the site. The objectives show that how much this construction can effect on climate change and human toxicity by building construction. The aim of this article is introducing the most friendly environment material for building construction and result shows wood building is the preferable solution

Numerical Investigation of the Effect of Open Holes on the Impact Response of CFRP Laminates

The presence of open holes changes the behaviour of composite laminates when subjected to mechanical loads creating critical zones with a high probability of interlaminar and intralaminar damage initiation. While open holes in composite laminates are a requirement in many situations such as assembly needs, wiring, and maintenance access, their influence on the impact response of composite laminates is still poorly understood. In this paper, a numerical study was performed on Carbon Fibre Reinforced Polymer (CFRP) composite laminates with open holes subjected to low velocity impacts. The influence of the distance between open holes to impact origin, hole diameter, and the number of open holes on mechanical response and failure was studied using a FE model based on the inter-fibre failure criterion of Cuntze to account for the progressive intralaminar failure. The interlaminar failure was considered by using zero thickness cohesive elements based on the cohesive zone model. The results showed that i) open holes change the shape and size of the damage caused by low velocity impact and ii) that the presence of an open hole close to the impact origin in-plane spread of damage is stopped resulting in more severe damage and a smaller projected damage area compared to the control specimen. In addition, the presence of open holes in most cases did not change the locality of the low velocity impact but rather changed the severity of the damage in the local impact zone

Economic and environmental life cycle assessment of alternative mass timber walls to evaluate circular economy in building: MCDM method

The construction industry is one of the largest consumers of energy and materials, which leads to it being one of the highest sources of environmental emissions. Quantifying the impact of building materials is critical if strategies for mitigating environmental deterioration are to be developed. The lifecycle assessment (LCA) consequential methodology has been applied to evaluate diferent methods of constructing residential double-story buildings. The ReCiPe methodology has been used for life cycle inventory. Three diferent forms of mass timber construction have been considered including cross-laminated timber (CLT), nail-laminated timber (NLT), and dowel-laminated timber (DLT). These have been assessed as load-bearing panels or wood frame construction. We evaluated the global warming potential (GWP), embodied energy, and cost to identify the building type with the lowest impacts. The results revealed that total CO2 emissions for mass timbers for the construction stage are 130 CO2/M2 , 118 CO2/M2 , and 132 CO2/M2 of the panel for CLT, DLT, and NLT, respectively. The embodied energy emission is 1921 MJ/M2 , 1902 MJ/ M2 , and 2130 MJ/M2 related to the CLT, DLT, and NLT, respectively, for this stage. The results also indicated that the carbon emission of DLT is lowest compared to the other two alternatives in the manufacturing and construction stages. However, when the entire life cycle is considered, NLT is the most favorable material. However, based on the life cycle cost (LCC), DLT has a lower cost. Finally, multiple-criteria decision-making (MCDM) was used to normalize the results and compare the alternatives. This showed DLT to be the best alternative, followed by CLT and NLT. In conclusion, the selection of building materials needs to prioritize regulations to reduce environmental and economic impacts

Strategies for reducing greenhouse gas emissions from residential sector by proposing new building structures in hot and humid climatic conditions

Malaysian government has advised builders to apply Industrial Building System (IBS) technique in construction due to so many advantages such as productivity, efficiency and cost. This study attempted to reduce greenhouse gas (GHG) emissions from building sector by representing two new building compositions into IBS structures categories. Life cycle assessment (LCA) tool Simapro.8 has been used to identify the environmental performance of buildings from cradle to grave. The full LCA has been run to assess the six different types of prefabricated buildings system, of which four are currently recognized and the other two are designed by current research. The primary result shows that timber prefabricate is the best choice due to having lower emissions toward climate change mitigation of building construction. However, timber houses have rarely been built due to some defects that occurred to its material and structure over time. Rate of applying wood in the construction industry in Malaysia has gone down from about 60% to 7% over the last 40 years. Therefore, this research aims to contribute to the body of knowledge by introducing new composite. First composite is Glued laminated timber (GLT) with steel stud and the second is a combination of laminated veneer lumber (LVL) with steel stud as two new compositions which not only have significantly less global warming potential (GWP) than prefabricated concrete structure or steel framing system, but can be replaced rather than abandoned timber structure. Therefore, new compositions can be suggested to house builders and facilitate the decision making process

Combinations of building construction material for residential building for the global warming mitigation for Malaysia

Global warming mitigation is used as a key to devise built environment strategies and sustainable policies in developed countries that aim to reduce the rate of carbon emissions. The goal of this research is to mitigate global warming from building construction by suggesting an alternative building scheme for Malaysia. A problem related to the building industry is releasing carbon dioxide emission. Use of timber for construction has less impact on the environment due to less carbon dioxide emissions, thus making wood the best material for wall construction. However, as the Malaysian climate is hot and humid, wood encounters many defects and deteriorates. Presently, most buildings in Malaysia are built from other materials such as concrete or brick. In the last 40 years, wood materials in building schemes in Malaysia have dropped from 60% to almost 5%. This research proposed a new approach to minimize the effect of CO2 emission for buildings as well as to improve their structural stability for a longer lifespan because these would encourage the Malaysian construction industry to use wood components in their building schemes. In this study, SIMAPRO Software was used to assess CO2 emissions caused by seven different types of building schemes in wall constructions. The results from a simulation of three time frames of twenty, one hundred and five hundred years showed that timber scheme is the best choice for construction. To promote the use of timber, a new building scheme that would solve the problem of timber wood structure in Malaysia were proposed. The alternative building scheme has combined precast concrete and timber (H8) to improve the timber scheme deficiency while releasing less CO2 emissions compared to other systems. Therefore (H8) could replace current building schemes. This research can facilitate decision-maker to choose the most flexible scheme for Malaysian housing. Thus, this system could be positively and widely used in the Malaysian construction industry